Drivetrain "thud"

I own an '04 Taco Prerunner TRD 3.4L SR5 Auto Trans with 52K miles, upgaded to Rancho shocks frt/rear otherwise everything is stock. What's the acceptable amount of vertical play in the carrier bearing? I can move mine about 1/2" vertically. I'm experiencing a "thud" of sorts after I've come to a complete stop (with pressure still on the brake pedal). Sometimes this doesn't occur until I lift off of the brake to start moving (before I even step on the gas), as if the drivetrain is unloading itself. It happens even with the rear diff locked and whether the truck is empty or fully loaded (approx. 800lbs). I've checked the motor/trans mounts/u-joints and rear-end backlash. The carrier bearing seems to be the only suspect component with all that movement but that should cause a vibration issue instead. This is the first auto-trans Toy I've owned, as well as the first with a carrier bearing, so I don't know if this is just a normal characteristic of the unit. Thanks in advance for any advice anyone can offer me on this subject.

 

Axle wrap, This is what you can do to help. http://www.tacomaworld.com/forum/1st-gen-tacomas/92105-zerks-grease.html

 

Its likely not your carrier bearing. The likely cause are your rear springs are forming an "S" shape under braking. The thump is the release of that twisted shape. As mentioned, the term "axle wrap" is a simple description of the S shape.

Typically, the carrier bearing will have a little play in it. A half inch is more than mine has but at least a quarter inch in every direction seems normal. You might also try lubbing up the slip joint on your driver shaft. That joint needs to move freely in and out. It does get a workout with worn, axle wrap prone springs.

 

x2
you nailed it buddy !!....

 

x2 on Digirat's post...

 

this subject sounds awful familiar....

 

That's EXACTLY what it feels like! Thanks for putting my mind at ease. It's been buggin the S>/T outta me for the longest time but I never wanted to start throwing money at the problem without a direction to go in

 

When I picked up my truck with 30K on it it had the thump. I greased the hell out of my yoke & it completely went away but only for a couple of months or so. Regrease again & gone again. After I threw on the Deaver leaf pack I no longer had the thump for years.

Just last month it started again but not nearly as worse of often as it did with the stock leafs. Can't believe it's been that long since I greased the yoke (shame on me for neglecting the truck). Regreased again a few days ago again, completely gone, even did some test runs by coming to a complete stop braking real hard (that's the real test).

I would say changing your diff oil would have nothing to do with resolving the thumping issue but it's worth a try & new oil in the truck as always good anyway.

Maybe your yoke is just gunked up, have you tried taking it off & cleaning out all the old grease that's hidden in there then repacking?

 

Man that just answered alot of questions for me!!! Thanks

 

I have a 99. Got it when it was one & half years old with 18,0000 miles. And its done it sins day one. I have done everything from taking it to the dealer to greasing the crap out of the yoke. I also did an AAL, and still dos it . So I feel that it is the tranny loads up and has to much presser down shift into 1st. gear. If you put it in nutral it dos not do it. So iam dont think is axle wrap. Sorry guys.

 

I am wondering if the manuals and automatics behave a little differently on this issue.

I have a manual, and when I installed my 5-leaf pack and greased my driveshaft yoke, this behavior and the thud (I think mainly caused by wrap under braking and then releasing at a stop) is largely, if not entirely, gone. But then MT Girl says she still has some, and she got the same 5-pack, but, she has an auto...of course, she has so many issues, I almost don't know where to start, but that is another thread, or several.

With the manual, the driver controls exactly when the clutch disengages when braking, but with an auto, the transmission does its own thing as you slow and stop and it unloads the drive train, and you can't do much about it.

Thoughts?

 

I think alot of this "axle wrap" is due to how fast you come to a stop. I come up to stops slowly and have never felt the problem before or after the addition of aal's.

 

...and you have a second gen. It is very common with first gens, I know.

 

I still think its in the tranny. ( auto tranny) reason being, that I think. Ever notice if your in neutral and you put it in drive how the tranny load up hard and kind of kicks ? I noticed no difference aftre installing the AAL. It is so annoying, it just pisses me off..

 

I have to agree with scocar and mtgirl. I've owned both (1st gens w/auto and w/5sp). Yes, some of it is from agressive stops but the axle wrap phenomenon (deformation of the rear leaf spring) is much more common on the autos and also easier to produce.

I suspect the reason to be an accumulation of wear and tear on the Tacomas notorious stock rear leafs.

To tacoma guy, no AAL is going to bring back the life to wasted rear springs. The only way you are going to get rid of your thud is to go to a set of quality replacement springs.