79 Georgie boy vibration starts at 65 mph

[kansascat]

 Was just wondering if anyone has encountered a drive train vibration that starts being noticeable at about 65 mph while under load...or under power versus coasting. It seems to go away when i let of the gas some and gets very noticeable by the time im approaching 70. I have a 30ft 79 model P30 chassis with 454 carbureated with TH400. It has just under 55k on it now. It did sit idle for over 15 years prior to me getting it and rebuilding the coach. It has new shocks, new air springs in front and air bags on the rear. New radial tires all around that were balanced when mounted. I cant feel any looseness in the U joints but have not removed the drive line and inspected each one by hand nor the carrier bearing. Below 65 it runs smoothly and drives nice. The vibration is best described as a rumble that can be both felt and heard. The sound appears to come from the engine compartment area and the feel is everywhere like coming up thru the floor. We have put about 4000 miles on it since its resurrection from the dead and this issue wasnt there that i recall at the beginning and seems to be getting more noticeable as miles go by now. I should add i also serviced the tranny before its first trip with new fluid and filter and added a second external HD tranny cooler with its own elec fan. My thoughts are either a bearing going out in the TH400, U joint and or carrier bearing thats rough but not loose to the feel, or maybe pinion bearing, but again cant feel it by shaking things by hand..Having sat idle so long i know bearing races could have been damaged by rust pitting due to lube not being run thru them. Anyone had and found the cause of a similar problem here? We have a large trip planned for it in late july so i need to find and fix it before then. Thanks guys.

[Rickf1985]

Sounds like the symptoms of a carrier bearing. A pinion bearing will do the same but that is real low mileage for a bad pinion. And the carrier is attached right at midpoint to the floor/frame. And a U-joint does not have to be loose to be bad, it gets dry first, then it brinnels or starts to break apart and then it gets loose. It is bad for a long time before loose is seen. Look for any rust stains coming from a joint or after a ride see if any of the joints are hot.

[kansascat]

I might just pull the drive line out and inspect the joints and bearing, maybe just replace them either way as im sure they are all original 1979 model parts. I figure the driveline is my best case scenario versus tranny tail housing or rear end pinion.

[Rickf1985]

Be sure to mark the entire drive shaft from end to end so that it goes back together exactly the same position.

[Hahn007]

I'm curious to see to see how this turns out as I am currently battling the same problem.

[EldoradoBill]

You can check the center bearing without pulling everything out. Get underneath and grab the driveshaft near the bearing and give it a lateral pull while watching where it goes through. Any noticeable slop, or if the rubber has deteriorated, and it's time to replace. may as well change the other joints while you have it out, they are inexpensive and relatively simple to replace and the section of shaft with the bearing needs to be separated anyways to press the new one on (and possibly the old one off).

[Rickf1985]

Have you priced those joints recently?!I am am not talking about the Chinese specials.

[EldoradoBill]

AC Delco Professional #45U0103 the greaseable kind I bought and replaced 3 @ $9.86 each I also bought and replaced a Timken center bearing that was $28

[cncsparky]

Kansascat, I took my driveshaft to Power Drive in Wichita.  They installed new Spicer joints, carrier, and balanced shafts for under $200. 

Also, you mentioned the rear tailshaft bearings on the TH400.  When I rebuilt mine, the two bearings in there were fairly rusty.  Could definitely cause a vibration.   The bearings (2) are National #109 and seal is National # 2457 or SKF # 21111

http://www.classicwinnebagos.com/forum/index.php/topic,9139.msg53438.html#msg53438

http://www.tpetruckparts.com/PowerDrive/DriveLine/

[legomybago]

Your screaming that old girl.....I feel bad when I approach 65 in ours W% The old 454 just buzzes..

[kansascat]

60 MPH in mine is only 3000 rpm. Those ole 454's will easily turn higher than that. In fact it seems to run smoother and better and make better power at about the point up to about 3400 range. I asked a few of my older racing friends and they all agreed that that rpm range was not a problem for them.

As for shaking the drive line feeling for looseness in the carrier or u joints, i dont feel any, but my fear is that since this rig sat idle for 16 years or so the bearing races may have gotten some rust pitting between where the rollers were sitting at. Im thinking they are still tight, but are now rough. Hope to get time to pull it out and inspect in the next week or so. will let ya know what i find.

[kansascat]

Rebuilt both drive lines with new u joints and carrier bearing and the vibration was a little better but still had the rumble at highway speeds while under load. opened up the rear dif and think i found the problem. One of the 3rd member carrier bearings had somelooseness to it and when spinning the dif by hand in one direction you could see the carrier move slightly and feel a rumble in it. Tomorrow morning i will finish installing another complete rear end that i had in a parts rv out back. It looked to be all good inside so i flushed it out well and refilled with new HD fluid. Got it bolted up to the springs before calling it a night. Will finish in the morning and take it for a spin. Fingers crossed.

[Rickf1985]

A rumble under load is usually a pinion bearing.

[kansascat]

Pinion bearings seemed to be fine, noloseness or roughness i could detect, but the left side carrier bearing had looseness in it which was allowing the ring gear to move slightly causing the mesh to be incorrect depending on load or coast. The repl\acement rear end i had in my burnt parts donor is in and the rumble / vibration seems to be gone as far as i could tell on the short test run i took it on. Flushed it out and filled it with a mixture of lucas additive and Mystic JT7 85w90 gear lube, put all new wagner thermo quiet pads on it and swapped over the new brake hoses etc from the original and i hope its good to go. Will soon know as we will be leaving on a 3 week trip towing a trailer with two small jeeps on it to moab utah and ouray colorado. Now im in the process of fixing a small crack at the top of the fresh water tank and a small leak in the grey water tank and installing a awning from the parts donor rig. Already put 3 window awnings on off of it. These should make it a lot easier to cool while in the dessert at moab. Anyone here ever use the plasti mend abs repair stuff. Its guaranteed to work or money back. Am going to try it on the grey water tank. The frsh water tank is polyethelene and from what i read they say the eterna bond roof repair stuff works well on that so guess ill try that. Already stop drilled the crfack and did my best try at heat welding the crack but think ill put the eternabond tape over it just to be sure. Thankfully it only leaked when the tank was filled clear full at it was right at the top onthe back side. Time will tell.