Adding overdrive, cost vs. benefits

denisondc · December 13, 2012, 03:45 PM

Sent: 8/5/2004 7:15 AM

Ian: You posed a good question. As far as a Spicer HD60 being the same as a Dana 60, I dont have any hard evidence, not having a Dana 60 to look at. But.... the Spicer 60 axles under our motorhomes have ratings like 6200 and 7500 lbs. The internet indicates the Dana 60 gets used as the axles under the front and rear ends of a 4wd Ford Bronco -- a vehicle whose gross wt is perhaps 7500 lbs and has a much narrow track than an M300 chassis. So I would suspect the axles are very different. If you find out, please let us know.

moparmotivator · December 13, 2012, 03:48 PM

Sent: 8/9/2008 3:20 PM

Now that fuel will probably never again drop below 3.50 a gallon again, has anyone installed an OD in their motorhome yet???

I picked up a browny aux. tranny this week. under, direct and overdrive with the shifter. Installation is a pain, but what isn't on these old boats. Heavy cables can substitute for the shift rods to help keep the shifter in a reasonable position for the driver. The tranny could be mounted where the carrier bearing is now with no clearance issues. Only major cost would be having the drivelines cut down and balanced. Give $50 for the tranny and $20 for a pile of extra drivelines and yokes.

The underdrive would be handy in some of the really hilly campsites in our area and the overdrive would have to help with fuel and keeping up with traffic without winding the guts out of the 413.

Has anyone tried this yet???

I would like to know how well the tranny would shift behind the automatic.
I don't expect to split shifts or anything like that, just be able to upshift ranges once rolling good in third on the automatic blipping the throttle to get in and out of gear.

I looked up the #'s on the aux tranny I have.

.86 over, direct, 2.14 under( creeper handy for launching boats and steep driveways)

not too radical on the overdrive but it would be nice for interstate travel in the old travco, the coach feels like it has plenty of power to pull the taller gears and it would get my interstate rpm back down to around 2750

uglydukwling · March 15, 2013, 10:16 AM

I'm in the process of installing an auxiliary transmission to replace the grenaded Gear Vendors in my Elandan II. I found a Spicer 5831, but it turned out to need internal work. It's just about ready to reassemble now. When I come to the installation, I can see it's going to be pretty involved. First, I'll have to fabricate mounting brackets. Then I'll have to devise a shifting system. And finally, there will be the driveline to match up. Since the 5831 is a lot heavier than the existing driveline, that means adapters. I'll probably have to make adaptor plates for the drive flanges. Adaptor u-joints don't seem to exist for such a large jump in sizes. (Any other ideas?)

I'm still considering the option of a 2-speed rear axle, as HeavyHaulTrucker suggested. The problem is that any that I've found are quite a bit bigger and have ratios that are low and lower. If you're sure that a near bolt-in with suitable ratios exists, I'll look again. Any suggestions as to what I should be asking for?

Part of the problem is that I'm not sure what axle I have now. My motor home is a '78 Elandan II, 27 foot (M500 chassis?). The closest manual I've been able to find is for a '77. My axle has a large 5-bolt pattern hub with 19.5" duals. If there ever was a tag on the axle, it's long gone. Can you tell me what axle I have, or should have, if it hasn't been changed? Model number and ratio would be good.

One thing that's a little perplexing and makes me wonder if I have the original axle, is that the way it's installed, it's impossible to adjust the rear brakes. The slot in the backing plate is tight against the spring. I'm going to have to service the rear brakes, but I guess that's separate thread.

If it looks like there's a chance of finding something, I'll get out my tape measure and start shopping again.

Elandan2 · March 15, 2013, 01:14 PM

The M500 was orginally equipped with a Spicer 70HD rear end with 4.56 gears. Rick

DRMousseau · January 05, 2015, 05:10 PM

I see so many of these posts regarding mileage.

Fact is, there are only two ways to improve the mileage of your vehicle. You either reduce the resistance against the horsepower you're using, or you improve the efficiency of which are turning gasoline into horsepower.

MOST folks want the latter, more horsepower per gallon will give more miles per gallon. Gasoline can only produce so much BTU per gallon. And the older gasoline engines are not very efficient at producing the horsepower we need and want. Typical older and common engines that are carbureted, are only about 25% efficient. SEVENTY-FIVE PERCENT of our fuels potential, is lost to heat and overcoming mechanical and physical resistances that are typical of internal combustion engines!!!

Given that most of are rigs weigh relatively about the same, and have very simular aerodynamics, road & tire resistance, mechanical drive-train resistance, etc,.... we can pretty much assume we all have the same horsepower needs. Oh yes, some have AC, air compressors, heavy alternators, and what have you,.... But even these luxuries will only require roughly 10% or so of the typical 300bhp that these engines typically turn out. And normally,... we see this all converted to about 7-9mpg!!!

Best way to increase milage?

Reduce the load and work being done! The GVW is pretty signicant here, but the added load of gas, water, food and equipment seldom amounts to more than about 10-15% of the GVW. Even I, as an old man, can push a 2000lb car!!! Most significant is aero resistance, which inversely increases with speed on "the big ol' box". EVERYONE will testify that jus cutting back on high-way speeds can significantly improve milage. Try standing on the top of your RV at 45mph,.... and imagine more than A DOZEN TIMES that power against the front end!!!! The drag behind us can suck up, into the rear bumper, a couple of close following motorcycles or a car totaling thousands of pounds. It's only a fraction of drag pulling back on the RV!!! But we're jus not gonna signicantly reduce ANY of these aero forces.

Increasing engine efficiency is about all we got. Electronic fuel injection computer systems can really help, by eliminating the errors of the unskilled operator and mechanic. Engine system modifications can increase the efficiency to produce horsepower,.... or rather "hp per gal",... which means we'll use less gas for needed hp, and more hp "in reserve" to fight those hills and headwinds!!! Even so, mods that boast a 10, 15, or even 20% increase in proformance,... are only a fraction of real engine efficiency, like 2.5%-5% of extra hp per gal!!!

Oh,... and those oversize tires, trans gears, axle and overdrive ratios??? The engineering of the whole design, is to run the engine at a speed that produces the needed hp that's required. To vary from that ratio design, won't increase milage, as we still require X amount of hp to do the work we need.

circleD · January 05, 2015, 06:31 PM

GEAR VENDOR!! Between the cost of unit and install verses the cost of all the mods and equations with EFI conversion, headers, cold air intake etc. It is the easiest upgrade and you can return to stock with a button. But you still have to drive right.

FastGlassman69 · January 05, 2015, 08:27 PM

Not going to happen my friend. If you overdrive while going down a mountain , possibly? But gaining that much MPG will not happen. I drove over the road for 25 years and always had overdrive transmissions, maybe 2 mpg difference between running without a trailer or with a load. If you put an overdrive unit in you better get a refrigerated transmission cooler , as it will cause more heat in the transmission. Don't think you'd ever recoupe the investment, might make it a little quieter at the sacrifice of engine and transmission wear/life! Good Luck whichever way you decide to go with it! Bob Hm?

FastGlassman69 · January 05, 2015, 08:41 PM

Quote from: DRMousseau on January 05, 2015, 05:10 PM
I see so many of these posts regarding mileage.

Fact is, there are only two ways to improve the mileage of your vehicle. You either reduce the resistance against the horsepower you're using, or you improve the efficiency of which are turning gasoline into horsepower.

MOST folks want the latter, more horsepower per gallon will give more miles per gallon. Gasoline can only produce so much BTU per gallon. And the older gasoline engines are not very efficient at producing the horsepower we need and want. Typical older and common engines that are carbureted, are only about 25% efficient. SEVENTY-FIVE PERCENT of our fuels potential, is lost to heat and overcoming mechanical and physical resistances that are typical of internal combustion engines!!!

Given that most of are rigs weigh relatively about the same, and have very simular aerodynamics, road & tire resistance, mechanical drive-train resistance, etc,.... we can pretty much assume we all have the same horsepower needs. Oh yes, some have AC, air compressors, heavy alternators, and what have you,.... But even these luxuries will only require roughly 10% or so of the typical 300bhp that these engines typically turn out. And normally,... we see this all converted to about 7-9mpg!!!

Best way to increase milage?
Reduce the load and work being done! The GVW is pretty signicant here, but the added load of gas, water, food and equipment seldom amounts to more than about 10-15% of the GVW. Even I, as an old man, can push a 2000lb car!!! Most significant is aero resistance, which inversely increases with speed on "the big ol' box". EVERYONE will testify that jus cutting back on high-way speeds can significantly improve milage. Try standing on the top of your RV at 45mph,.... and imagine more than A DOZEN TIMES that power against the front end!!!! The drag behind us can suck up, into the rear bumper, a couple of close following motorcycles or a car totaling thousands of pounds. It's only a fraction of drag pulling back on the RV!!! But we're jus not gonna signicantly reduce ANY of these aero forces.

Increasing engine efficiency is about all we got. Electronic fuel injection computer systems can really help, by eliminating the errors of the unskilled operator and mechanic. Engine system modifications can increase the efficiency to produce horsepower,.... or rather "hp per gal",... which means we'll use less gas for needed hp, and more hp "in reserve" to fight those hills and headwinds!!! Even so, mods that boast a 10, 15, or even 20% increase in proformance,... are only a fraction of real engine efficiency, like 2.5%-5% of extra hp per gal!!!

Oh,... and those oversize tires, trans gears, axle and overdrive ratios??? The engineering of the whole design, is to run the engine at a speed that produces the needed hp that's required. To vary from that ratio design, won't increase milage, as we still require X amount of hp to do the work we need.

I certainly agree with you, as in my tractors with 400hp Caterpillar engines in them cruise was at 1800 at 60 mph, if I pushed up to 70-75 my fuel milage decreased rapidly as I had to push a wall of air all the time, loaded or empty! Don't think you can force a gas big-block that is geared to cruise at 55-60 @ 2500-2650 and drag it down with Overdrive to 1800 and make it magically get 9-11 mpg, in fact it will probably get worse if not on flat ground with no headwinds or any hills! Just an Old truckers opinion! Bob

FastGlassman69 · January 05, 2015, 08:48 PM

Quote from: uglydukwling on March 15, 2013, 10:16 AM
I'm in the process of installing an auxiliary transmission to replace the grenaded Gear Vendors in my Elandan II. I found a Spicer 5831, but it turned out to need internal work. It's just about ready to reassemble now. When I come to the installation, I can see it's going to be pretty involved. First, I'll have to fabricate mounting brackets. Then I'll have to devise a shifting system. And finally, there will be the driveline to match up. Since the 5831 is a lot heavier than the existing driveline, that means adapters. I'll probably have to make adaptor plates for the drive flanges. Adaptor u-joints don't seem to exist for such a large jump in sizes. (Any other ideas?)

I'm still considering the option of a 2-speed rear axle, as HeavyHaulTrucker suggested. The problem is that any that I've found are quite a bit bigger and have ratios that are low and lower. If you're sure that a near bolt-in with suitable ratios exists, I'll look again. Any suggestions as to what I should be asking for?

Part of the problem is that I'm not sure what axle I have now. My motor home is a '78 Elandan II, 27 foot (M500 chassis?). The closest manual I've been able to find is for a '77. My axle has a large 5-bolt pattern hub with 19.5" duals. If there ever was a tag on the axle, it's long gone. Can you tell me what axle I have, or should have, if it hasn't been changed? Model number and ratio would be good.

One thing that's a little perplexing and makes me wonder if I have the original axle, is that the way it's installed, it's impossible to adjust the rear brakes. The slot in the backing plate is tight against the spring. I'm going to have to service the rear brakes, but I guess that's separate thread.

If it looks like there's a chance of finding something, I'll get out my tape measure and start shopping again.

It would be really cool if you could find a Spicer airshift auxiallary, no linkage to worry about! As Far as flanges most of the big truck flanges of the bolt on type could have say a 1/2 piece of flat steel bolted and welded to them and then find the flanges you need to adapt that bolt to those plates and be balanced along with the shortened driveshafts. Would love one of those for my rig if only for the nostalgia of days gone past! Old trucker dreams! Bob ps if you send me a PM I will draw you up what I am talking about.

Rickf1985 · January 06, 2015, 07:06 AM

OOOORRRRR, You could eliminate the automatic altogether and adapt a 13 speed to the engine and you are done. I bought some parts off of a Dodge dually pick-up that a guy had put a 13 speed into. I was offered the whole trans setup at an attractive price but at that time I did not have the RV and had no desire to put a 13 in a truck that would only need about four of those gears. W%
As DRM has pointed out about the engine efficiency there is only so much you will gain. What has not been mentioned is increasing the old style engines efficiency. You can buy a complete kit from companies like Edelbrock that have the headers, cam, intake manifold, carburetor and even heads if you really want to go all out. This is a complete dyno matched setup for low end grunt power. I used to build these engines before the complete kits came out and you can get better mileage and power. The key word is power, most people tend to use that extra power to excess and there goes the mileage gains out the window. A motor built like this is designed to be in it's best power band at a much lower RPM than your average engine. There are take aways though as there are in any modification. The power will drop off fast above about 2500 RPM which means that if you are trying to pass someone going up a hill it may just fall flat at around that rpm. This is where the overdrive comes in. As you can see it gets REALLY expensive to save gas and I like to refer to it as dollars per mile of savings as opposed to dollars per mile spent before modifications and where is the breakover point.

HamRad Mobile · April 19, 2015, 05:22 PM

Good morning;

Surprising that I had not noticed this particular message thread until now.

First, in the interest of public disclosure, no, I do not yet have an overdrive on my 1987 Winnebago Elandan WCP31RT. However, I can say that the comments about trying to put an overdrive behind a weak engine are valid comments. And, I can tell you why I am putting some money into this system:

I am in the middle of a multiple step process to prepare the entire engine and drive train for working with the Gear Vendors 3D0475 22% overdrive. A comment about that 22% reduction in comparison with the common 30% reduction often found:

When I took the numbers for the gear ratios in the GMC 3L80 (also known as the THM-475 or the Heavy Duty THM-400) three speed automatic transmission, and calculated the resulting gear ratios for Low or First, First Over, Second, Second Over, Third, and Third Over, the numbers came out in a very nicely staged 22% drop in each gear up to the Second Over to Third shift where the drop is only 15%, but that smaller drop is right where you want it to be less as your vehicle speed increases and the required horsepower rises as you go faster, or, to put it another way, the gear ratios are closer together as you get to the top. Again, this is with the GMC 3L80 or THM-400HD or THM-475 transmission.

Probably the best way to summarize this is by saying that it provides a very nicely staged 5 speed transmission with an overdrive on it.

I have not calculated the resulting gear ratios with other transmissions.

Being able to drop back to Second Over is very nice for climbing hills and other similar places. I have wound my way up to the top of Stevens Pass in normal Second at 42 MPH. It will be nice to do that at 50-55 MPH or so. Yes, I am installing the controls to manually (pedally with a foot switch?) call for the overdrive shifts. And I will be less of a mobile road block.

Then when you are cruising on level ground and you do not need as much horsepower and torque to move you along, you have the normal 22% drop when you shift from Third to Third Over. Then you get the full normal engine speed reduction with less engine noise and wear than when it is cruising at 3200 RPM at 60 MPH and the tachometer drops to 2500 RPM on the torque curve with the overdrive, but with my vehicle with about a 0.34 drag coefficient, I think it will pull it nicely. This is where I expect to also see some improvement in fuel economy.

One observation about the reliability of the Gear Vendors overdrive is that the recommended fluid change interval seems to be routinely ignored. Sort of like most of the other fluid changes in the rest of the driveline.

Again, the overdrive is the final step in my process once the engine is improved and the transmission has the additional cooling capacity added. I am in the middle of the engine modifications now.

The first change was the fitting of another distributor in place of the GM HEI system. The new distributor allows me to run a CDI box with it. The stage in progress right now is the installation of a modified Gale Banks Engineering 49052 "PowerPack" intake and exhaust kit. Once that is in, then I think that it will be ready for the Gear Vendors overdrive after this Summer. There are some family activities that must be accommodated during the Summer. Finally, there may be installed an aftermarket electronically controlled TBI fuel injection system, but I do not expect to see any real performance improvement from that over a clean and well adjusted Rochester Quadra-Jet four barrel carburetor, except for the ability of the TBI system to automatically adjust the air/fuel ratio with a change in altitude when driving in the mountains; something the normal four barrel carburetor cannot do. That is the only performance improvement that I can see getting from the TBI system. However, the O2 sensor mounts are going onto the exhaust system now so that I can monitor what the carburetor is doing at this time, and the exhaust system will be ready for the addition of the TBI fuel injection system if it does go in.

All of the aftermarket replacements or add-ons that have been purchased, and will be purchased, will come to a little over $10,000.

Not included in all this calculation is the additional instrumentation to watch the engine speed, the automatic transmission fluid temperatures, the real-time monitoring of the air/fuel ratio, the direct readout of the current fuel economy performance, and some other parameters.

Will these pay for themselves over time from a possible resulting saving in fuel costs? Probably not over the period I will be driving it. However, the ability to cruise with less engine noise, and to climb more efficiently, and to keep the engine on the optimum point on the torque curve for the driving condition, along with the probable extension of the cruising range from one filling of the gas tanks, is something that is not easy to measure in terms of a dollar value.

Probably my main goal is to just be able to say that I have improved the efficiency of my motor home recreational vehicle so that it is no longer as dependent on fossil fuels as it was, and I can say that I did that. And I must also admit that it does cost something to make the performance something like what we are getting from the newer motor homes available for sale today. All I am doing is taking advantage of some of the advances in automotive engineering and technology that have been made in the last 25 years. However, all this is still less than the cost of a new similarly equipped motor home being sold today. And there are some other reasons why I do not want one of the taller motor homes being sold today. Yes, there are some personal and emotional reasons why I am doing this. To many people, that may not be rational or logical. OK.

And, finally, all of this is still a lot less expensive than the child support that I was paying for over 22 years. You need to keep things in perspective, guys, and not look at just one aspect of the problem.

Enjoy;

Ralph
Latte Land, Washington

circleD · April 19, 2015, 09:33 PM

Get a Gear Vendor and keep it at 60 or slower. Cruises down the interstate nicely. For the money and hassle free its worth it.

eXodus · April 20, 2015, 06:47 AM

IMHO for 10,000$ i would swap in a diesel with a 4 or 5 speed automatic.

but that's me i just plain love diesel.

Rickf1985 · April 20, 2015, 08:23 PM

Remember that 13 speed I was talking about? Behind a 24 valve Cummins? W% Did I ever mention I was a truck driver?

DRMousseau · April 21, 2015, 12:25 AM

Unlike gasoline engines, where we struggle with heat issues, Diesel fueled engines utilized the heat of high compression and tend to be more efficient than gasoline fueled engines. Diesel also has more BTU potential per gal than gasoline. While we need the same power to move the weight and overcome wind and rolling resistance of our RVs, we typically see better mpg from diesel powered rigs. It also seems the efficiencies of diesel power are much preferred in most countries outside the US, where here, we only use it for dependable "heavy" work.

The uniqueness of diesel engines and fuels, is where "overdrive" has it's greatest advantage. Such engines produce their greatest power at a much lower RPM than gasoline engines. Diesel engines can also utilize "blowers" and "turbines" with greater efficiency than gasoline engines. Multi-geared transmissions are an advantage in BOTH, gasoline and diesel powered rigs, allowing us to keep engine rpm in the best range for the power needed,... higher rpms for gasoline engines, and lower rpms for diesel powered engines, within their unique limitations of course.

I suppose I'd still see my 85mph speed limitation in the old Winnie, whether it was gas or diesel powered. But not many folks to pass on our highways at that speed anyways! LoL! But I find the Dodge 440 with the 727 trans in my D20 is actually perfect. Plenty of power to pass when needed, and plenty to maintain uphill speeds wherever I go. And reasonable expected mileage. Kinda makes me miss my old "'Runner"! Can't really imagine a smaller engine! And if I DID have the smaller engine,... I'd likely consider some modifications for the briefly needed extra power. But NOT at the expense of overall milage or stock performance!!!

Yup! Bettin a couple 20# bottles would get a little engine and me over the hills and around those slow rigs on the highways,.. jus not so quick off the light in town! So what!

eXodus · April 21, 2015, 07:21 AM

back to the overdrive:

I've got the 4L80E:
1 2 3 4 R
2.48 1.48 1.00 0.75 2.07

When I cruise in 4th (3+OD) around 60 I'm getting 10mpg, even with an added 5500lbs horse trailer (and drag) still getting 8 mpg out of my TBI.
The 4th with 0.75 makes it really less noisy to cruise.

Why not change the gearbox to a 4 speed instead of an overdrive ? You can get used automatics for really cheap.
Just found they make aftermarket valvebodys for the 4L80E so you can engage the overdrive in every gear - basically getting a 6 speed.

Rickf1985 · April 21, 2015, 10:57 AM

You are confusing overdrive with torque converter lock up. Overdrive is another gear, fourth in your case. Engaging fourth gear anywhere other than after third would just bog. You can lock the converter manually with a switch in any gear and that will be something that Ralph is going to miss out on. Locking the converter manually will also give better compression braking going downhill. Without the lockup converter you will always have a higher engine rpm than what the gear charts are saying you have because of converter loss. You are also going to have much higher transmission temps for the same reason.

Froggy1936 · April 21, 2015, 12:13 PM

Just a note : With any lock up convertor equipped veh , If the lockup valve sticks or is electronicly abled in the lockup position You will have no convertor slip as soon as veh is put in gear engine will stall (same as letting out the clutch suddenly at a stop without acceration ) This will also cause a stall when comeing to a stop . If its an electrical problem you can just pull wires to correct but you will lose all lock up . The problem parts are inside the tranny ! Frank

Rickf1985 · April 21, 2015, 12:39 PM

I have mine set up on my Dodge dually on a switch on the dash. The lockup command from the computer grounds the solenoid in the valve body, all you are doing is bypassing the computer and grounding the solenoid manually. And yes, it will stall if you stop. You have to have a modified valve body to get it to lock in first or second though. You cannot simply add the switch and get 1 or 2 lockup. I personally see no need and it is just inviting broken parts. Another issue to be aware of is locked up shifts. 3-4 shift while locked at normal throttle is no issue but if you are full throttle and the rpm is up there and you are full into the power band it is going to hit fourth gear really hard, not good. You have to be aware of what is going on if you are controlling it manually.

eXodus · April 21, 2015, 01:20 PM

no manual for me. hey i wont do anything to my rig until something brakes.

the 6 speed conversion of the 4l80e comes with a new computer, so I'm guessing they figured it out somehow. Probably they shift the normal gears first and then see how the throttle reacts, and then shift the OD gear. i know a overdrive is also a gear but it is behind all other gears.

a lot of front wheel drive cars gearboxes have these concept, 3 gears with Od but here it is to save room.

Rickf1985 · April 21, 2015, 03:24 PM

The 4L80 is a 4 speed with lock up. No extra gears unless a separate gear box has been added to it.

Froggy1936 · April 21, 2015, 04:14 PM

Exodos, you might be confusing standard transmission OD which was on the rear of the 3 speed tranny, Actually the 4L80E overdrive planetary is in the front section of the trans & 4th (OD) is the very front clutch assy Frank

eXodus · April 22, 2015, 06:42 AM

Yeah I'm good in confusing.
I'm coming from a different culture and learned on different cars. We had a couple of cars where a certain "gear" inside the transmission is called an overdrive.

I'm thinking about when I hear overdrive about a gear which affects all gears.

Back to topic: I would rather change the transmission instead of adding a separate unit behind it. (maybe a transfer-case for installing 4 wheel drive

)

GONMAD · April 22, 2015, 07:13 AM

Froggy is right about the 4l80e, the planetary for the OD is in the very front of the rotating mass carrying the entire assembly into overdrive instead of just the output shaft. I have often wondered just what the logic for this was. It took a lot for me to shell out the bucks for the Gearvendors but I have yet to regret it. Just the noise level reduction was worth it!

circleD · April 22, 2015, 09:03 AM

I'm with GONMAD on that. If I turn off the gear vendor while driving it gets loud in the living area. But with it on the noise is like cruising at 30 mph. It cost alot for it but you can move it from vehicle to vehicle with some adaptation especially if you know a good drive line guy. But I understand what you're wanting and its hard to find a balance.