95 Caprice 4L60E Tailshaft Bearing Thumping Noise?

Chris

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I have a 95 Caprice that started to make a droning noise around 25mph to 50mph. The pulses increase with speed. It lasted for a couple weeks and turned into a slight vibration in the floor board. I put the car in the air and let it idle in gear. Groaning sounds could be heared from the rear axle. I knew the spider gear pin was loose, caused by a worn case, and causing a little play and I had a rebuilt Auburn diff in the garage so I thought it was time to do the swap. New bearings, shims, and seals were installed including axle bearings. I left the car in the air and let it idle in gear and everything is quiet. Three days later the drone came back and is now a thumping noise at 20 to 35mph which does go away above 35mph. I tried riding the brakes a little to see if it was caused by calipers or rotors but it didn't have any effect. I can only feel it down by my feet. I put the car in the air and idled in gear and the rearend is quiet. U-joints are good. You can see a little movement at the tailshaft yoke when pulling it up and down by hand but not a lot of play. I have 3/4" extended rear trailing arms and a stock drive shaft. I just read this can cause the tailshaft bearing in the transmission to wear out. Would a worn tailshaft bearing cause this knocking noise? Anybody have any ideas? I just road tested and put the transmission in neutral at 35mph and it didn't have any effect on the noise.
 

jasonn20

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If the tailshaft bushing was bad then the driveshaft seal would leak. Is it leaking ??

In what condition is the trans mount in ??

If all this looks good then dropping the trans pan and check for excessive wear. How many miles ??
 

Chris

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Hello,
Rear seal has a light film of dirt around the seal but doesn't look wet or have any drops. No signs of spray on the underside of the car either.

Mount from what I could see is ok. Bolts tight, slight movement when I push up on the tail shaft. Idled up a little and put the car in drive and reverse with no banging sounds.

Bought the car from the Highway Patrol with 102k miles. Now has 228k miles. Has only had 1 fluid change and I had to replace the 1-2 shift solenoid about 2 years ago. Where on the inside of the pan would I be looking for wear? Can the rear bearing be seen through the bottom of the unit?

Thanks for the help!!
 

jasonn20

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The tail housing does not have bearings it has a bushing. The trans does have needle bearings but you would have to tear it completely down to get to them.

Doing a sump exam to see if there is excessive bushing material, metal, clutch material etc.. If a component is failing then there is using evidence in the pan.
 

Transman

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How is the exhaust system? If an exhaust pipe is touching any frame piece then you will get a drone & vibration noise. The drive shaft may be hitting the exhaust also. You will need to exert extreme care and keeping safety in mind, put the car on jackstands to see if you can duplicate the rumble with the suspension "loaded". How experienced are you at differentials? I'm not trying to be offensive but your problem may still be inside the diff. also. They aren't as simple as they appear. Post results, Transman
 

Chris

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I already put the car back in the air before I got a chance to read your replies. I had loaded the suspension like you mentioned and didn't get any vibration at 30-40mph. Living dangerously I took it to 90mph and had a definite vibration in the cab, however, it was hard to pin point it under the car. The diff didn't vibrate but I could feel it in the frame rails and the tranny crossmember. I believe I felt it in the tranny pan also but no positive indicator that it was the transmission at fault. With the wheels spinning so fast I didn't want to spend to much time under the car so my observations were rushed.

Also, on the road the sound is as if there was a flat spot on one of the tires. Only the vibration goes away as you speed up instead of getting worse. I rotated the tires front to back but it didn't change anything.

I have rebuilt a Chrysler 8 3/4" diff and helped my friend rebuild a Chevy 12 bolt with no problems. This is only my 3rd time at rebuilding a rear end. Everything is new except for the ring and pinion gears. Back lash and wear pattern were good so I went ahead and reused the gears. No offense taken. I appreciate the help!! I also noticed today that the posi moans if I turn at an idle. If I turn and coast into a driveway like normal it's quiet. If I go real slow it moans. Is this normal?

I'll put the car in the air again tomorrow and check the exhaust pipes and hangers. I'm sure nothing was touching the drive shaft but not sure if the pipes were hitting the frame or floor pan.

I have to wait until Friday to pull the pan. I work 6AM to 4:30PM and it's getting dark by the time I get home.
 

Mobile Dan

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Exhaust rattles can change with torque load and temperature. Hot pipe = long Cold pipe = short Put in gear, step on throttle = exhaust will rise, drop, or twist
 

Chris

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Checked exhaust and nothing was hitting. Had to drive the car to work and noticed a random tshhh sound and clicking at low speeds. Figured it was the tranny and went ahead and ordered a rebuilt one with all the upgrades, sunshell,servo,etc. $850 outright w/torque converter. Good price for my location. Anyway, had to drive the car to work again and everything was smooth but on the way home the left front bearing totally blew. Never felt any shaking in the wheel or pulsation in the pedal just bearing chatter and the car started to pull to the left. Lucky I wasn't going fast. I was able to clean the spindle up enough to throw a new bearing on and get it home but the spindle is shot. The bearings are only about 8 months old (Autozone) and they were the very first thing I checked when the whole vibration thing started. I'm picking up a spindle today and getting the car back on the road. I'll let you know the results if the vibration is gone. Thanks for following up!!
Just thought of something. A front bearing wouldn't cause a vibration when the car is up in the air and the drivetrain is spinning. Du!! So I guess I'll still have the problem. I'll keep you posted.
 

jasonn20

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how did you tighten the wheel bearings?? If you get them too tight they will fail prematurely.
 

Transman

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Although anything IS possible, the noise you describe is more likely coming from the diff rather than the trans. I've had u-joints cause strange noises and my first diff that I overhauled, I forgot to use Locktite on the ring gear bolts. One of those backed out and made a strange noise that came and went until it backed out far enough to hit everytime around.
The wheel bearings need to be tightened properly or as Jason said, they will fail very quickly. Tighten them very tight with a wrench or socket then loosen them 3/4 of a turn or so, then bring them back up with your fingers. Do NOT take them tighter to the next hole of they don't line up for the cotter pin. These are "Zero Preloaded" bearings. Post back, Transman
 

Chris

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Okay, Bearings I spin the wheel and tighten the nut. Back off a half turn and tighten by hand. Replaced the front spindle assembly/ABS sensor and the front end is fine. Still had vibration. Opened up differential and everything looked okay. backlash was .009 - .011 checked in three spots. I was going to play with the shims and try and tighten it back to .008 but when I pulled the right rear axle I noticed pitting in the bearing area. Bearing looked fine. I guess I overlooked it when I replaced the diff with the posi unit. Bought an axle repair bearing from NAPA for $12 and I'm back in business. Drove a 10 mile loop and so far no vibration or droning noise. Forgot how quiet the car used to be :) I also put in some limited slip additive even though Valvoline says it's made for posi rearends and it is also quiet. I'll post any updates hopefully all the problems have been corrected.
I did have one more question on the differential. The Auburn instructions say the torque for the pinion shaft retaining bolt is 20-25ft lbs. Chilton says 8ft lbs. I went with 20ft lbs and threadlock. Am I safe or is the bolt going to snap and work its way out?
 

Transman

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Great news on the axle bearing!! Backlash should be ok if no growling noise, differentials are sensitive to this BUT not subtle if unhappy, YOU WILL HEAR NOISE! LOL.
I am "Assuming" the pinion bolt that you are referring to is the bolt that goes through the pin that holds the side gears (C-clips) in place. The Bolt will break when the pin wears the case, allowing too much side movement. Since the diff is new, this problem is a LONG way down the road. I also agree with the additive. Great work and Good luck, Transman
 

Chris

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I drove the car to work today and didn't have any problems. Amazing how much noise a little pitting on the axle will make! Everything is quiet again. No growling from the rear end or differential. Thank all of you for your assistance!!!!
 

Transman

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Thanks for the update and great work. You now know what a little pitting can do. It can be hard to explain to some customers why that little bit of roughness can make such a horrible noise! Transman
 
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