Hard 'clank' when putting into reverse _sometimes

[bobehud]

Most times its when the carb is in fast idle,can feel as well as hear it.
With basically a broken neck (fused all but one vertebrae ) i cant crawl under it.
But i have been fixing other peoples noises a long time.First thought was u-joint,second thought was trans mount,third and the expensive thought
was rear axle.Would not be the first time i have seen a fresh rearend have the pinon nut back off a tad.

Took it on the hiway run it up 75mph or so a just lifted let the chassis unload..didnt hear a thing, hard start from stop even enough to turn a tire and to a quick lift nothing,no noise.was not being silly was loading and unload rear axle.

All windows down,running next to concrete divider no 'bounce back' noise.


Lay it on me guys.

 

[89Suburban]

Mine does the same thing. Usually only if I drop into nuetral while coming to a stop, stopping, then putting it into reverse, I get a clunk, I can tell it's the drive shaft, like somebody hit it with a hammer.

Or if I sit in one spot and shift it back and forth from f to r it will do it. BUt driving it seems fine and tight, no looseness letting off the gas and hittting the gas.

 

[Old77]

Do either of you have a shift kit by chance?

 

[Irishman999]

I had the same issue with mine, when shifting gears occasionally I would get the hammer sounding ping sound on the drive line. I put a new U-joint in and it stopped.

 

[89Suburban]

Do either of you have a shift kit by chance?

I don't think so.

 

[bobehud]

I dont have a kit either. I treated this noise like it was someone elses truck....been doing this way to long...going to take it in to one of the garages i run and leave it....
i swear its a very metallic CLANK and only in reverse..AND it doesnt do it every time.

 

[78shortandwide]

I would say u joint, even if you can't physically feel the slop in the u joint/drive line it could still be bad.

 

[89Suburban]

I would say u joint, even if you can't physically feel the slop in the u joint/drive line it could still be bad.

Yeah, I can't feel any slop in the u-joints, they can still be bad? I'd figure they would start squeaking if they were bad or you could feel play?

 

[HotRodPC]

Reverse gets twice the fluid pressure so if you do have a U joint going bad, Reverse will find it quicker than any other gear. Also, check your fluid level. If fluid level is Low or High in a th400 it can cause a hard reverse too. There is such thing as hard reverse correction kit for Th400's too.

 

[crazy4offroad]

Chock the wheels and put it in neutral when you check the u-joints, you cant tell **** if it's in park.

 

[Old77]

Chock the wheels and put it in neutral when you check the u-joints, you cant tell **** if it's in park.

I say DON'T chock the wheels but do this but then take vids of you chasing your truck down the street!!!

 

[bobehud]

The extra pressure in reverse would make a weak link,or u joint as the case may be will show up and it's that KINDA noise.
Besides it never hurts to put good u-joints in.Just drove it...took it for a ummm..spirited test drive and didnt feel any shake from the drive shaft..

and me chasing that thing...lol..nope id just sit down and wait until it hit something big enough to stop it

 

[83K5guy]

I know all of my chevys do it my 83 not so much it doesnt move very often, my 98 and my 05. I have been told just normal GM driveline clunk. I have seen people on other forums drill and tap then put a grease zerk on the driveshaft yoke that comes from the trans and apply a little shot of grease to it and then it goes away. I replaced all my u joints on my 98 and still did it took To have rear end checked (backlash) and even the dealer heard it but couldn't do anything for me

 

[HotRodPC]

The extra pressure in reverse would make a weak link,or u joint as the case may be will show up and it's that KINDA noise.
Besides it never hurts to put good u-joints in.Just drove it...took it for a ummm..spirited test drive and didnt feel any shake from the drive shaft..

and me chasing that thing...lol..nope id just sit down and wait until it hit something big enough to stop it

Yep, that's what I'm saying. It could be a tired U joint, not noticable going into any other gear, but will the extra pressue, hitting a bit harder then its noticeable. You're right, it never hurts to replace U joints if its been a good long while since they were done.

 

[dhamp]

My Chevelle does that, but it's got a pretty stiff shift kit in it. It'll bark the tires going into R or D. It's done that for as long as I can remember. Did your's just start out of the blue doing that?