Clunk on take-off...sometimes

[KivaKid]

Sometimes, not always, if i take off quickly I get a *clunk* in the rear end. I thought it was a loose spare underneath, took that off, still there. It's not really as metallic sounding like u-joint *clank*. Maybe tranny mounts?? Axle..spring....?

[AzFrank aka Desertson]

Hey KivaKid,
the two things that come to mind are 1)rear wheel bearings or 2) if you have a Quadra-Trac its the chain,its stretched.
The second one happened to me.Sometime I would take off from a dead stop and I would hear a "clunk" or if I was going up a rough hill at low speed and needed a little more throttle it would clunk do to the chain slipping over the gears.
1)Drian your T-case and insert a dowl rod or screwdivre thru the drain hole.
2) Push it up until you feel it just touch the chain.
3) mark the dowl rod.
4) Push the dowl up on the chain as far as it will go and mark it again.
5) if there is a 1/2-3/4" difference betwwen the two marks, your chain is toast. :(

[jode]

Sorry for the bad news, but I'll have to second the diagnosis for a slipping chain.

If you determine that it is the chain, replace it ONLY with a MORSE brand chain!

I got majorly burned on this issue and ended up doing the same job twice and buying two separate $hundred+ chains. learn from my mistake!

BTW, replacing the chain is a 5-hour driveway project for an inexperienced wrench. I had never seen the inside of a t-case B4 that day and (with the instructions located on this very website smile.gif ) I was able to get the job done.
:D
Good luck!

[Don S]

Originally posted by KivaKid:
Sometimes, not always, if i take off quickly I get a *clunk* in the rear end. I thought it was a loose spare underneath, took that off, still there. It's not really as metallic sounding like u-joint *clank*. Maybe tranny mounts?? Axle..spring....?..
KivaKid:...
... If you get two bangs quickly in a row then it would very likely be the chain. Here is a link with about three ways to test for chain problems. If you swap out the chain I can find more tips to help.
... If you drive easy you can still go a very long way but don’t go on the trails at Ouray with a bad chain.

link>QT BW-1339 TESTING (http://groups.msn.com/JEEPTECH101/jeeptech.msnw)

Good Luck ;) and CUL.. ds..
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link> Vote for the JEEP of the MONTH (http://www.auburn.edu/~hawkijf/test.html)

[Kukur]

I have the same noise intermittently on my 78' Wag.

When it is making the clunk, I can get the sound to recreate itself by sitting in the driveway and shifting from D to R and back.

Could this be the slack in the chain being taken up by the change in tranny gears?

Why would something like this be an occasional 'problem?' Would it be the differences in RPM?

[CowKiller]

i will give u a hint!
if u have the low range unit, make sure it is fully seated before tightining the bolts. i did this and snapped the case, luckly i was at tech school and had welding weld it back up

[sailingjeep]

Kukur: I've noticed mine has the D-R-P clunk hardly at all when it is cold. What's up with that??

[OldBlueCherokee]

probably a stretched chain in the quadra track transfer case--->SAME PROBLEM WITH MY 76 CHEROKEE

or worn input splines in the low reduction unit (if you have it)

or excessive backlash in the ring and pinion.

[MrWagoneer]

ditto for me sailingjeep, if cold, no clunk when going to reverse.
when warm i get the clunk when going to reverse.

someone said i may not have the correct fluid for my transfer case, i may need the expensive quadratrac fluid, however from reading other posts, i gather i may not need it since i have an aftermarket hi and low range lever in my centre console (with free wheeling front hubs).
ie. the clutch has been removed from my transfer case.
75 wagoneer.

[ December 10, 2002, 05:01 PM: Message edited by: MrWagoneer ]

[Kukur]

Trifecta. Only after it has been on the road awhile. Otherwise she is fine.

Dunno why. Fluid warming up and getting less viscous? Chain warming up and expanding?

I have no idea what fluid is in mine. Or if I have the reduction unit. I know she has the 4H/4L lever under the driver's seat. I am still learning what is in this girl. I have only had her running for a couple of months.

I do know one thing. I really am starting to appreciate my Dana 300 w/ Tera Low gears in my CJ7 a lot better now.

[KivaKid]

Well, I drove around the entire day, using the Wag as my work vehicle to see if I could hear it again. Not once did it make this noise. I really don't believe it would be something that's worn out on a vehicle with only 63,000 miles!! I know the chain life isn't super long, but........

[Kukur]

I know what you mean. It was doing it all day Sat. so I figured I would crawl under it Sunday and have someone shift it in/out of gear to see if I could hear where it was coming from.

It hasn't done it since Sat.

[sailingjeep]

I'm pretty sure I've got the right fluid. ATF in the NP 229? I had a drivetrain guy rebuild my tranny recently(another problem) and swap in a different rear axle. He gave fixing the clunk a try but couldn't figure it out. A lot of folks say the clunk is normal and to live with it.

[MrWagoneer]

was searching thru the forum and found this posted in another thread.

http://www.4wheeloffroad.com/editorial/article.jsp?id=23658

"The only transmission used with the Quadra-Trac was the General Motors TH400 three-speed automatic with a bellhousing pattern unique to the AMC engines. The tailshaft is the only other nonstandard GM part—it’s a 10-spline shaft that sticks out a good foot from the rear of the housing. This shaft drives the sun gear in the reduction housing, or the drive coupler in the units without low range. The coarse nature of the 10-spline shaft wears on itself and the sun gear, causing a loud bang when it’s shifted into Reverse."

i just luv this forum :]

[CowKiller]

just a side note, i have been told the qt chain should be replaced every 50000 miles. i was told it is a bad enginerring deal.

[Kukur]

Mr Wagoneer, nice detective work!

So for all intensive purposes, if we have atleast 150k on the drive train (not sure if it is more because it only reads six digits 00000.0) then there probably IS slack in the QT chain.

And there is probably some slack between the output shaft on the TH400.

Or a combination of the two possibly.

Great! Just finished putting in a new engine and I was hoping to take the little bit left over and put a lift kit on. Guess that may have to wait.