A727 to A518 Transmission Swap?

[thisoldhippy]

Was wondering if anyone has thoughts on a518 tranny swap into their winny?

Great article:Big block a518 overdrive conversion (lots of pics)

[Wantawinnie]

I am close to pulling the trigger on a Cummins swap in my Chieftain. The main concern I have is using the A518 overdrive behind the Cummins and that version was beefed up some over the gas version and also features a non lockup torque converter. The overdrive section seems to be the weak spot on the A518 and my worry is the heavy weight and wind resistance that the overdrive will experience. In truck use the overdrive is not recommended for towing. In a Class A 440 application you will be dealing with a lot of weight and engine torque at the same time so whether a "stock" small block A518 will hold up is questionable. They can be built to handle more but that can get expensive real quick. I would consider a deep tranny pan, trans temp guage, a big fan cooled trans cooler at a minimum.

[thisoldhippy]

I actually have an Isuzu 6bd1t built in1986 that I bought to put in mine! It came with a ford 4 speed behind it! Thought about doing a manual but the clutch thing got out of hand! Then it was about an allision 1000! Cost was really big! The a518 came up next! I tow a 16' trailer so total weight is right at 20,000lbs! Talked with a guy on cummins 4bt and he says that it will handle the weight! So I am kind of confused! 

[Wantawinnie]

The A518 is basically a 727 with a rear overdrive section. The overdrive section is generally considered the weak link. It may work fine for you but 20000lbs. is a lot to ask out of a stock one and is way over the original GVW of the trucks that used them. If you only pull overdrive on level roads that will help.

[chicknnhead]

i have researched this many times, and can never seem to pull the trigger. i can't really see a fuel savings to warrant the cost. I think the only thing your really saving is the motor working so hard. i est the gain on fuel mileage would be 1-2mpg

[thisoldhippy]

Have a friend in Idaho has an 30' winny like mine did the cummins swap with a 5 speed and now averages 14! Took it to mopars on the strip with a car trailer and 7 people 28,000 gross worst 12 best 18! 

[thisoldhippy]

Wantawinnie what tranny are you thinking about? 

[Wantawinnie]

My situation is a little different because I have a gear vendor unit that I got off Craigslist. If I keep the 440 I will be using an original 727 with a gear vendors unit and the original 4.56 gears. The gear vendor features a 0.78 overdrive and would drop the rpm around 700 rpm at highway speeds.

I have a A518 out of a 1992 Cummins and the gear vendor unit that I would use in the diesel application. With a Cummins diesel the 4.56 gears in the rear are not the ideal setup for highway crusing and the gear splits are not very good even with a 0.69 overdrive A518 due to the limited rpm range when not in overdrive. If it will hold up the A518 and a gear vendors overdrive behind it will give nearly perfect rpm range at all speeds. With the double overdrive the 4.56 gears will work well on the highway and off the line performance will be good.

The other alternative with the diesel swap is to use a 1989-90 Cummins 727 3 speed and the gear vendors unit with a rear end swap to 3.54 or 3.73 gears. I feel this would be the strongest and most reliable alternative for me but the gear swap and purchase of another transmission would be required.

Just to be clear, the diesel transmission case and some internals are different than the small block version and neither will bolt up to a big block without specific adapters.

If you are looking at a diesel swap and do not have a transmission yet the 47RH from a 94-95 Cummins diesel features a lockup torque converter and is supposed to be an improvement on the A518. They are more costly to build though and the good aftermarket converters are very expensive.

 

[thisoldhippy]

Actually I don't have a tranny yet! Been researching and starting to think that it may be better to go old school turbo 400 and a gear vender overdrive! Just wanting to do some thing I know will hold up without the guess work! New to this diesel thing!I drag raced for many years and know that the 400 will take the pressure of towing as will the overdrive! Appears a rear gear change would have to happen also! I put in a ? to Monstertrans to see what they say about their a518 1600$ I will let you know what I hear!

[Wantawinnie]

If I were starting from scratch I would go with a 3 speed and gear vendor and change the rear gears just for simplicity and durability. You can then split gears from 2nd, 2nd over, 3rd, 3rd over as well depending on your driving needs. The Turbo 400 is a popular tranny and I see gear vendors units for sale with those adapters on Craigslist a lot more than the Dodge versions.

[Oz]

One thing which seems to be apparent from reading the posts over the years is that, given the engine is in a good state of maintenance and tuning, even the most expensive modifications yield minimal improvements in mileage on their own, singular merit..  Maybe 1 or 2 mpg or maybe only a half a mile per gallon.  Don't forget, we're starting with small numbers to begin with ( 6 - 8 mpg).  So, in order to make the most of what we've got to work with, you need to be prepared to possibly spend some substantial time and funds to make improvements and be prepared to see very small improvements as significant.   Two miles per gallon better over 5,000 miles of driving is a BIG improvement, isn't it?

The other factor is, in the long run, will the modifications pay for their cost in terms of better fuel efficiency?  In many cases, depending on just how much you spend to get 3 or 4 gallons per mile better, you still would have to drive 100,000 miles for the benefit to justify the cost.  If not, then you'd be better off just sticking with a well tuned, mildly improved engine and making sure the other factors which affect fuel efficiency are just as well maintained.  Whenever you "hear" someone else say they get fuel mileage which is well above the norm, remember that it could be due to the area they drive and well, some people do have a natural tendency not want to say they're getting soaked at the gas pump and may embellish their actual experiences a little.  This is certainly not to say it's not possible to get significantly better mileage.  It has been proven with documented data from reliable sources that it is possible but, there are many factors involved.  The exact same modifications on the exact same make, model, size, weight, etc RV can result in completely different results due to the variable of driving terrain and driving habits.

So, I've always wondered about this transmission swap myself.  One would think it would improve your gas expenses because of the overdrive but, I would also reasonably guess that it all depends on how and where, and how frequently you drive your RV.  In mountainous areas and traveling mostly short trips, I don't think it would make much difference.  Maybe in the west and areas where there are a lot of long, flat or low rolling hill areas, over many miles, the savings would be noticeably better.

[thisoldhippy]

I live in eastern Oregon! Not a lot of serious mountains 4800 to 6000 feet! We are at 4148 here! I am an artist so I make my money doing shows in Oregon,Nevada and Idaho would like to branch out more into Washington and Colorado! Have already tried headers and a new carb gained maybe a mile to the gallon! Looking at the diesel swap for the power and mileage! Tranny is out in the winny so I have to replace it any way! Get really tired of pulling the hills at 30!! Figure if we can get the power and pickup the mileage to say 12 it would be worth it! Although I must admit I have to wonder if I need to work with the gas a little more! The 4.56 just kill this poor engine!     

[Wantawinnie]

If you stay with a 440 there is no need to change the 4.56 gearing when using the A518 transmission. The 0.69 overdrive yields a final drive ratio in the 3.15 range. I would be a little hesitant as that seems almost to high IMO, especially for the Class A rigs running taller 19.5 rims and 33" tires. This is another reason why a gear vendor with a 0.78 overdrive yielding a more realistic 3.56 final drive ratio would be my first choice. 

I have ran a bunch of rpm spreadsheets researching this and it is a balancing act keeping all the variables in order to ensure the engine operates in its optimum torque curve.

[ClydesdaleKevin]

I'm all ears on this one.  As full timers and doing our own shows all over the country, in our case Renaissance Faires, we do put on a lot of miles on our RV.  About 8000 miles a year actually.

We get 7-8 miles to the gallon, depending on what part of the country we are in, which is pretty respectable with a 35 foot motorhome, loaded down with not only our fulltimer living stuff, but a full wood shop, a display tent, and towing a 5700 lb Jeep Cherokee.

Just to keep the math simple, lets call it 8 miles to the gallon, at 8000 miles a year.  So that means we use 1000 gallons of gasoline a year, and if gasoline costs 3.50 a gallon, that means we spend 3500.00 a year in gasoline for the RV alone.

Now, if we were to do an engine mod, and it brought it up to 9 mpg, we would then be using 889 gallons of gas, which at 3.50 a gallon now means we would only spend 3111.50 a year, for a savings of 388.50 a year, which is pretty significant.

At 10 miles to the gallon, we would use 800 gallons a year, costing 2800.00, for a total savings of 700.00 per year.

At 11 miles to the gallon, we would use 727 gallons a year, costing 2544.50, for a total savings of 955.50 per year.

At 12 miles to the gallon, we would use 667 gallons a year, costing 2334.50, for a total savings of 1165.50 a year.

So you can see, at least with the amount that we drive, it would be cost effective to spend the money to make some improvements, as even just a 1 mpg improvement would save us around 390 bucks a year. 

The problem is, of course, that while it would eventually pay itself off, engine and transmission mods that actually work and really do improve fuel economy significantly are ridiculously expensive! 

So now that you've been patient with my math, I do have a question for you.  The Gear Vendor overdrive...just how much to they cost for a Turbo 400, which is what we have in our RV behind our Chevy big block 454?  We travel a lot out west, especially the trip out there, which is a lot of flat nothing going through Louisiana and Texas...then turns into mountains in earnest once we hit New Mexico and Arizona.  And how hard are they to install?  Is it something a decent home mechanic can do, or does it require special tools and know-how?  I'm very interested in the prospect, especially after doing the math...lol!  If it could improve fuel economy just 1 mpg, it might be worth it if the cost of the mod wasn't astronomical.

Also, how does the Gear Vendor work exactly?  Does it work automatically with the gear shifter for the stock transmission, or does it have its own controller?  Is it installed inside the housing of the stock transmission, or is it installed after the rear tail cone, between the transmission and the drive shaft?

Any mod I make has to pay itself off within a few years, but something like this might be worth it, depending on cost.  This is the reason I'm hesitant about doing anything else with the fuel intake on our motor...switching to aftermarket fuel injection or even TBI costs upwards of 3500 bucks, but you would be lucky to see a whole mile per gallon improvement, and more realistically, from the research I've done, it stays about the same, or maybe a half mile per gallon, which even with the way we drive would take years to pay for itself.

Getting the 7-8 mpg with our heavy rig and toad to me is pretty good, showing that our motor is tuned as optimally as it can be, and not much else I do under the hood is going to milk it out any better.

But an overdrive?  Especially with the roads we travel out west?

So yeah, how much to these things cost?  How hard are they to install?  And what gains could I realistically expect in MPG by installing one?

Sorry for rambling on, but this topic really interests me...

Kev

[thisoldhippy]

Hi Kev: From what I can see about the gear vendor it has a lot more advantages the just overdrive! It is controled by a control box that has an automatic or manual feature! It actually turns your 400 into a 6 speed i.e 1st 1st over-2nd 2nd over etc1 Thus you can also split gears when you are in the hills as well as just over drive when it applies! It bolts on as a replacement for the tail shaft! I have been in this game for many years (hot rodding)! But seems that any competent home mechanic can handle it! Drive shaft will have to be shortened! They aren't cheap! I figured around 3500$ with a new tranny!

http://www.gearvendors.com/ This is their website! Lots more info there!

[Wantawinnie]

The gear vendor is expensive new. There are deals to be had on the used market. I bought mine off craigslist last fall attached to a freshly built bigblock Chrysler 727 for $450 and the guy included a nice set of 440 RV headers. Shipping cost another $200 so I am all in for around $650.

[thisoldhippy]

Wantawinnie: I got an answer back from Monster! They say that the a518 won't handle that kind of weight! Am going to put the diesel in it! Starting to think that manual might be better with the weight thing and towing! Although I'm with you the turbo 400 with overdrive seems good also!

[ClydesdaleKevin]

So if I were to find one used, I might be able to get one for around 500 bucks, which would be well worth the money.  As far as replacing the tail shaft, I think I could handle that, and then bring the driveshaft in to be shortened. 

I take it I wouldn't be able to use the parking brake though if it replaces the tail cone?

Kev

[ClydesdaleKevin]

Holy crap!  I went to the website...3400 bucks brand new!  Then figure another 300 bucks to modify the drive shaft...

Even with the miles we put on 3700 bucks would take years to pay off, so there is no way I'd spend that kind of dough.

Now, if I found one used for 500 bucks or so, then that would be a different story altogether.

Kev

[gadgetman]

Thats a kewl set up ! Wish I had money to burn ! I would put one on mine. Finding a used one and then buying their 700.00 adaptpr kit would be an option. I like it ! Anyone have 4k  they want to get rid of ?? 

[thisoldhippy]

Ok! So I talked with a guy here in Oregon on the cummins 4bt site! He builds a adapter to turn the back of my Isuzu into a cummins so I can put a 96 or newer 46re behind it! This has a lockup converter and uses a electric box to control the tranny! Will have to change the rearend gears Adaptor qwith all I need is right at 600$ Then the tranny out of 2wheel drive about 600$ Much less then 3000$ or more! So at least I have a direction now! He says should get 12-15mpg! Will keep everyone posted!

[Wantawinnie]

I wouldn't go 46RE as they are the gas version and you are going to have to run a computer controller. The 47RE and later 48RE were the Cummins versions if you go that route.

If you use a 1994 or 1995 47RH (H stands for hydraulic) it will shift old school in all gears but overdrive. Overdrive and lockup can be run by pressure switches or simple toggle switches if you want manual operation.

[thisoldhippy]

Ok! He explained a bunch! I will check on those! Thanks 

[Wantawinnie]

You should start a diesel swap thread so that we can start documenting the details involved with such a project. I planned to do that if the Cummins swap happens for me. I am still on the fence as it is a fairly involved task and I would like to get camping before my 4 year old graduates high school.  :)rotflmao

[ClydesdaleKevin]

So I actually sat down and did some more math...and calculated the actual number of miles we travel in the RV a year, including a few hundred extra miles for potential side trips, and the total was quite a bit less than my estimated 8000 miles...5935.85 to be exact.  So yeah, it would take even LONGER to pay off an expensive mod. 

Thanks Dave for that link!  There are some on there, even a new one in California for 2500.00...still too much, but a grand cheaper...so its something to consider some day if I run out of other stuff to do... :)rotflmao

Yeah, like that will happen...lol!

Kev