fflumpy

Hey guys, been chasing down vibration in the drive train of my stock 85' C4.

I replaced u-joints on the drive shaft, replaced the slip yoke, bushing, seal and had the drive shaft balanced. Was definitely worn and needed replacing but didn't completely fix the problem…

So I replaced the u-joints on half shafts and I noticed that both yokes going into the rear differential (off the half shafts) was a little loose… I can shake them up and down with a clunking noise. I'm thinking this is the drivetrain vibration that I've been looking for.…

This is where I need some of the expert opinions Here…

How easy is it to remove the yolk from the rear differential? I know there's a bolt holding it on…is it similar set up to the slip yoke going into the transmission where it slips over a spindal with a bushing (of course not a slip in the differential)? Or is the gearing on the yoke? Can it be slipped out or do you have to remove the differential and take it apart to get the yoke out?

I am obviously not a differential guy… any help would be greatly appreciated.

Thanks

WVZR-1

Differential assembly needs to be removed to service the seals/bearings for the "short-axles". Is this an A4 (D36) or a 4+MT (D44)? The "short-axles" are retained in the differential by selective thickness snap-rings.

fflumpy

Not sure.…hiw do i find out that info? On the differential? Or on the sticker in the rear storage compartment?

…i have to remove the whole differential out of the car and basically do a re build?

WVZR-1

Yes needs removed from the car. Is your car an automatic or a 4+3 manual?

RichS

You basically need to take it down to this to pull the stub axles out. You will need a stout pair of snap ring pliers to get the axles out.
Auto: Dana 36
Stick: Dana 44

fflumpy

4+3

fflumpy

great…lol…does it have bushings in the housing like the tail of the transmission for the slip yoke?

RichS

All replaceable bearings and races for the pinion and carrier. Roller bearings for the axles. You could buy rebuild kits with everything included from places like Denny's, Randy's, Tom's differentials.

WVZR-1

Well with the 4+ it's a D44 so I'd suggest you do whatever very soon. You don't want it to explode or get worse. Out of the car it would be very easy to remove the short-axles and evaluate what you've got. If the short-axles are good then it's a matter of bearings and seals. I'd consider buying the pinions, the washers and the pin maybe BUT after evaluation maybe you'll find you don't need. These rears deserve "maintenance" but seldom do they get it. They're run until busted way to often. Lots for you to consider!!

fflumpy

well it makes sense to replace it all while i have it out. Like i said before im not a differential guy…but im handy and i have the factory shop manual…do u guys think this is something i could handle? Or get it done by a pro?

jv9999

If you haven't done diffs before, have it done. The Dana being aluminum needs to be spread to setup properly. You'll have lots of fun just trying to get those selective snap rings out. Been there, don't want to go back. :-)

WVZR-1

I believe that you remove it from the car and evaluate what you're "needing". Once evaluated I believe you "then" determine if you'd like to attempt the "maintenance" or if it's maybe a "for hire".

Judging from the way you approached the drive-shaft repair, balance of and replacing bushing, seal etc. I'd say you're likely very capable.

How many miles on the car?

Once the short-axles are removed and visually inspected it will be more obvious as to the extent of the required service.

fflumpy

Well…the speedometer "reads" 65k. Not sure on actual miles

WVZR-1

Being an "early" D44 and the pinion being shimmed vs a crush-collar I'd think you're likely very capable of the "evaluation" your self and very likely the bearing/seal and whatever the evaluation seems to indicate. If you're not rushed I'd say consider it. Might have been good to have been done over the winter BUT I'd say you CAN'T wait until next winter.

fflumpy

I talked with a guy at a rack&pinion shop by my house…he seemed to be pretty knowledgeable on c4's. He stated that you should not be able to move the yoke up and down…
BUT he also stated that he highly doubts that that is the source of my vibration…?!?

What do u guys think? Think bad bearing in the diff could cause vibration?

jim2527

Go through all the vibration tests before you get into the diff...

Find the sweet spot for the vibration then drop into neutral. If the vibration goes away its Engine/transmission related.

Swap wheels left to right, if the vibration goes away it wheel/tire related.

Does the steering wheel vibrate? Can you feel it in the brake pedal?

fflumpy

The vibration stays in neutral. Sometimes it's bad sometimes it's not to bad…i had the tire/rims "road forced" balanced…so im thinking that its not the tires. Rims are offset so i cant go fromt to back with them. Yes the steering wheel shakes back and forth. Nothing in the brake pedal. Hand the rotors turned last week.

jim2527

ok so...swap wheels left to right but do front then rear but not both ends at the same time.

steering wheel leads me to think it's up front somewhere. Do a thorough suspension check... ball joints, tie rod ends, bearings, control arm bushings etc.

fflumpy

Ok thanks for the info…i check the front end and did not find any obvious issues. Had a shop look at it and they said it was something in the drivetrain which has lead to me finding issues like drive shaft, bearings, u-joints…differential! Lol.

I will try the wheel swap and ill check the front end again.

Thanks again…going out of town for a while will update when i get it done