5rebel9 Posted July 14, 2025 Report Share Posted July 14, 2025 Well chalk it up to another UNcommon problem to show up on one of my AWD journeys. This time it's a transfer case going bad on the WIFE'S '13 RT. with brakes applied and shifting to drive and then reverse it makes a clunk sound just like a bad U-joint on a traditional RWD driveshaft. The output flange for rear driveshaft moves about 45* when doing so. Also clunks on acceleration from cruise while in motion.My friend is going to replace the transfer case and rear motor mount for a grand and 2 chicken BBQ dinners! 2late4u 1 Quote Link to comment Share on other sites More sharing options...
John/Horace Posted July 16, 2025 Report Share Posted July 16, 2025 The clutch on the front of the rear rear diff is usually the big issue with the awd system clunking. People call it a viscous coupling but it’s actually activated by the electric plug on the rear diff. The input seal leaks diff gear oil into the front cover that holds the clutch. Wrecking normal clutch functions. Clutch bearings also fail sometimes. I had the two lip seals on the diff half shafts on each side fail at just over 100k miles. Time consuming but not expensive fix (the rest of diff is still working ok) So changing out entire rear diff with a good used one, is probably a good idea when the clutch coupling goes. The front ptu’s usually hold up if we keep a proper fluid level in them. Minor drip on one seal on mine, I just keep dumping and refilling every 3 years, no dipstick for measuring. Will be interesting if the ptu/transfer case is your failure making the clunk, along with the worn out rear engine mount. Sounds like a great price from a friend. Quote Link to comment Share on other sites More sharing options...
5rebel9 Posted July 16, 2025 Author Report Share Posted July 16, 2025 7 hours ago, John/Horace said: The clutch on the front of the rear rear diff is usually the big issue with the awd system clunking. People call it a viscous coupling but it’s actually activated by the electric plug on the rear diff. The input seal leaks diff gear oil into the front cover that holds the clutch. Wrecking normal clutch functions. Clutch bearings also fail sometimes. I had the two lip seals on the diff half shafts on each side fail at just over 100k miles. Time consuming but not expensive fix (the rest of diff is still working ok) So changing out entire rear diff with a good used one, is probably a good idea when the clutch coupling goes. The front ptu’s usually hold up if we keep a proper fluid level in them. Minor drip on one seal on mine, I just keep dumping and refilling every 3 years, no dipstick for measuring. Will be interesting if the ptu/transfer case is your failure making the clunk, along with the worn out rear engine mount. Sounds like a great price from a friend. Well aware of rear diff/coupler concerns, but this is definitely the transfer case up front. Rear motor mount is high mileage and rubber got soaked from 2 cracked oil filter housing failures. It is actually in decent shape as there is very little engine/trans rock from mounts, just doing it with the transfer case being out for preventive reasons and already have the part and a lot easier to do. I'll keep all here updated as to how things go. Quote Link to comment Share on other sites More sharing options...
5rebel9 Posted July 22, 2025 Author Report Share Posted July 22, 2025 Well...... Since diagnosis was done with the car on the ground and watching gear engagement with my friend laying on the ground, he got "snookered" by saying it was the transfer case/PTO. He got it on the hoist to start the job and found the source of concern at a much easier fix and parts cost. It was a worn out passenger side CV joint and support bearing. replaced the whole right axle for $250. Picked it up today and wife is HAPPY to have her car back. She enjoyed my chauffeuring her about, but did not enjoy the high step in for front seat entry of the G Caravan wheelchair van I now have to use with my dad. My Buick is awaiting new rear springs and locator links for rear toe, between HER DJ the van and my son's DJ that needed repairs and my friends FULL shop workload the Buick has been on the "back burner". When he does get it done, then it also goes in for 4 wheel alignment and tires!! Quote Link to comment Share on other sites More sharing options...
John/Horace Posted July 23, 2025 Report Share Posted July 23, 2025 Much cheaper fix, so a win. On mini vans I have done that fix a few times. Don’t like the Cardone reman shafts, I normally use the brown box new shafts. Often Mexico stuff. Fewer issues generally. Quote Link to comment Share on other sites More sharing options...
5rebel9 Posted July 23, 2025 Author Report Share Posted July 23, 2025 10 hours ago, John/Horace said: Much cheaper fix, so a win. On mini vans I have done that fix a few times. Don’t like the Cardone reman shafts, I normally use the brown box new shafts. Often Mexico stuff. Fewer issues generally. Indeed it was much less costly! My DJ's are all over 150k miles but have only had one outer cv joint fail. And with all the FWD rides I've had , I can't recall that I've ever had joint troubles. Yes it was the inner tripod joint and support bearing that "gave up", a rather odd failure to occur, outers seem more prone to failure. I agree in feelings of Cardone shafts from my years as an active auto tech. Quote Link to comment Share on other sites More sharing options...
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