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swebster · 08-13-2003, 07:37 AM

Does anyone else get a "whirring" sound from their driveline while coasting? I've noticed a pretty substantial whirring noise and corresponding vibration in the pedal and steering wheel in the 345 when I match the engine power exactly to the driveline speed. Sounds kind of like a low volume version of driving over the rumble strip on a highway shoulder. In fact the first time I heard it I thought that's what happened.

I can even move the sound and vibration in and out by increasing or decreasing the gas pedal at highways speeds. It only occurs within a very narrow range and lasts only a second or two. When I'm on the gas or off the gas it does not happen at all but I can hear it when applying power from a coast (engine braking downhill to full power uphill).

It's very noticeable at higher speeds (70 mph) but not nearly as bad at 60 or 65. I'm thinking it could be U joints or something else in the driveshaft itself or maybe an input shaft?

Please chime in with any similar experiences or advice. As always it will be greatly appreciated.

jaiman · 08-13-2003, 07:51 AM

It sounds like the beggining of a U-Joint starting to go. I'd have it checked immediatley and replace before its too late. You can somewhat check it yourself by putting the tranny in park engine off. and trying to rotate the driveshaft back and forth. There shouldnt be much if any side to side movement.

Jai

swebster · 08-13-2003, 07:57 AM

Thats what I was thinking too. When you're driving along at 11:30 at night through PA going up and down hills, listening to this noise you start to imagine all of the spinning parts under there and how bad it would be if you blew a U joint on the road. I'll get under there tonight and check it out how much play is in the driveshaft.

jaiman · 08-13-2003, 08:02 AM

not very much at all. There shouldnt be any dead stops in the play either. Try to manipulate the drive shaft right near the U-Joints so you can hear any bangs when it stops moving. Chances are it is the rear one but make sure to look at them all.

Jai

wb13798 · 08-13-2003, 08:06 AM

you dont want to drop a drive shaft. your wallet will cry. i would also check the carrier bearings . lol
al

swebster · 08-13-2003, 08:28 AM

Quote:

Originally posted by wb13798
you dont want to drop a drive shaft. your wallet will cry. i would also check the carrier bearings . lol
al

Beyond the incredible noise this would make, followed closely by an over rev'd motor and transmission, you all would hear a very loud cry from me!

I'm trying to be as proactive as possible on this new to me MH and replace anything critical and suspect right away. So far, I've been lucky as things are in better than expected condition. The best part is that NAPA has almost everything needed on the chassis and the parts are el cheapo to buy!

jaiman · 08-13-2003, 08:33 AM

The wonders of a P-30 chassis never cease to amaze. Its nice not having to shed a tear everytime you need to buy something. Napa is just down the street from me, with the exception of a belt length everything they have sold me fits like a glove. I even whined enough that they give me jobber pricing now.

jai

swebster · 08-13-2003, 08:43 AM

You are definately right about the P30. Part of our decision to go with the AS was this chassis. I threw an alternator belt in a SOB diesel pusher once in MA and couldn't find a belt for 100 miles! Ended up finding one in a storage bay, but it scared me enough to adopt the KISS concept for my own MH.

Seems like our AS has the right combination of ride quality, reliability and parts availability for us DIY owners. Makes me wonder why so many modern MH's have such overly complex chassis and systems.

jaiman · 08-13-2003, 08:58 AM

Amen!

74Argosy24MH · 08-13-2003, 09:27 AM

Start it, hold the brakes on and go from drive to reverse a couple of times and listen for a clunk. If it does it is probably a U joint. If not check the carrier bearing and your rear axle lube.

John

swebster · 08-13-2003, 05:33 PM

There is a definate clunk sound when going from drive to reverse and back. More on the reverse to drive than the other way around. So...I'll order U joints tomorrow. I haven't crawled under there to look at them. Any tricks or special tools needed?

wb13798 · 08-13-2003, 07:33 PM

before removing the drive line mark every thing and make sure it all goes back like it was. or you might have a balance problem. i would go ahead and replace the carrier bearing while you have the drive line out. lol
al.

PeterH-350LE · 08-13-2003, 07:54 PM

Don't be surprised if the clunk is still there after replacing all the u-joints. The biggest clunk is probably coming from of the differential.
I once went thru replacing all the u-joints, carrier bearings and had the driveshafts balanced and still had the 'whirring' at a certain speed. Brought it to a drive line shop and they found a worn yoke at the transmission.
Remember the park function doesn't work real well with the drive shaft off

dinoburb · 08-13-2003, 07:55 PM

The clunk you heard might be the transmission yoke fitting in need of some serious lube. Very common problem in the GM world of 454/TH400 combination. So along with the u-joints I'd make sure the yoke and splines are well lubricated. This clunk will return so plan on an annual re-lubing!!

Hope that is of some help.

Take care,

Sean

swebster · 08-14-2003, 07:47 AM

Great advice from everyone. My whirring occurs at different speeds and rpms and seems to be related more to the relative speed between the driveline and the engine, so I'm not ruling out balancing, but I'm looking for a mechanical culprit first.

If I'm under there I might as well replace the carrier bearings, check the diff fluid levels and the lube the trans yoke. Like my Dad told me, you can do it right the first time or you can do it again! I'll be sure to chock the wheels (all of the wheels) and mark the relative positions on the driveshafts before disassembly.

I figure if I replace all of the bolt on stuff and it's still whirring then I'll bring it to a truck shop. An advantage to living in Louisville is that we are a huge distribution/logistics point so there are many very good truck shops in town.

This must be payback for how easy it was to get the gen, fridge, airs and plumbing working! I'm cabin camping this weekend in Indiana so it will have to wait till next week

Do you know if NAPA sells the carrier bearings? They have part numbers for U Joints for the 86 P30 ($7.99 each). Are they the same all the way down?

PeterH it sounds like you've done this at least once. Any tips, suggestions, caveats?

thenewkid64 · 08-14-2003, 08:39 AM

My .02 worth.

Take the drive shaft out, load it in the truck and take to a napa that can press out the U-joints and do the carrier bearing. They will stock them. They can also do the rebalancing of the shaft.

There sometimes is a mix and match going on with the U joints.

This way you eliminate 5 pieces that could be problems.

Chuck · 08-14-2003, 08:48 AM

geez, I never heard of a NAPA shop that can do that stuff...not around here, anyway. My brother-in-law specializes in driveline repair and so forth. One of the reasons he's so busy all the time is that he's one of the very very few people around here that can actually DO it. (and metro-boston ain't small).

jaiman · 08-14-2003, 08:51 AM

Great advice Brett. Its really not that expensive of a repair. One that I personally would leave up to professionals.

Jai

swebster · 08-14-2003, 08:58 AM

Brett,
My neighborhood NAPA is also a machine shop so I like this idea a lot. We are also extra lucky because one of their Distribution Centers is ten minutes from my office so getting parts should not be an issue.

The last thing I want to do is turn this into a bigger problem. I've replaced U Joints in Jeeps and pickups but never on something as big and heavy duty as the AS. I'll check with the NAPA guy this afternoon and see what they can and can't do. I like the AS because so many repairs and improvements fall into the DIY category, but I know when I'm in over my head!

thenewkid64 · 08-14-2003, 09:01 AM

I am speaking from experience. I did a carrier and 2 u-joints on the 76 and it was a bear.

The carrier on the 78 had to pressed on and off. The NAPA shop in north Dallas could do it, but they may send it out. I had the carrier pressed on at a small parts shop in Duncanville, TX. The U joints and balancing were done when the engine was replaced as part of the driveline upgrade.