Al Sanchez

I have a 1972 cutlass 350 with th350.. The transmission has been rebuilt the car runs good and shifts good but when I put it in drive it makes a hard loud clunk. Has any had this problem? All I can think of is that it feel like if my idle is too high.. My rpm in idle is 800 and 600 in drive but like I said it clunks real hard.. Any advice will be appreciated

Allan R

Check 2 things
1. Trans fluid
2. u-joints front and rear.

Al Sanchez

I will check the fluid.. The u-joint are new and where checked not to long ago.. As for the fluid will too much make it do that

Alex72cutty

I just had the same problem with my cutlass. Put it in drive and you hear," Clunk" Also, when I started to take off it sounded like two knifes rubbing against each other, and finally when I got up to about 65mph it started to vibrate. All causes of bad U Joints.

Al Sanchez

I might take one more look at the u-joint but they where replaced before I rebuilt the transmission.. Then the rear seal started leaking so when I took it back to the transmission shop I had them double check the u-joints since the drive shaft was of the car and all was good.. The car runs good and shifts good had it on the freeway 90+miles and it runs smooth just when I put it in drive it.. Clunks..

D. Yaros

If it is not the U-joint, which I and everyone else seem to think it is, then perhaps the transmission rear mount is not tight?

Al Sanchez

I'll double checked the rear mount but I'm pretty sure that it nice and tight we double checked everything not too long ago when I had the on a lift. Later a friend is coming over and I'm going to have him shift in and out of drive and see if I can see or feel where this noise is coming from

Tony72Cutlass'S'

My car also does a Clunk when i put it into drive...

My trans fluid was changed last year.

Does anyone have a detailed write-up on how to change U-Joints.

Allan R

Tony, are your u joints original? If they are it's a bit more work because the plastic seals have to be heated till they ooze out. You won't get them out unless you do that. If they've been changed already all you really need is BFH.

Tony72Cutlass'S'

I've still got the balljoint press from my suspension adventure!

That's what i've been looking for... I have no clue what you guys mean by heating, do i need something intense like a MAPP gas or is propane fine?

I might remove my driveshaft tonight (Since it's snowing.....) and see what gives.

Allan R

If you take the driveshaft out, have a good size catch basin handy. When you pull the splined end the tail shaft will puke about 2 L of tranny fluid. Yes you will need Mapp to heat it hot enough to ooze the plastic. There are how to vid that show how to do it. Still on the IPad right now or I'd link one for you.

Tony72Cutlass'S'

No worries Al! I'm still at work

I looked this up in the CSM... Since i'll be down there, i may as well do the transmission mount too...

M-38 Turbo Hydramatic Transmission 350

From Rockauto...

ANCHOR Part # 2378
3 speed trans.; w/ M38; Automatic trans

Octania

if you can...

get it on a lift.
apply brakes
operator moves from R to D &c. while observer looks for the noise/ lost motion of the clunk.

Is your car officially a "clunker" then?

Motor mounts, final drive gear slop, could be lots of things. U-Joints most common, and new is NOT the same as good.

455man

I was going to mention to check motor mounts also.

Tony72Cutlass'S'

What do you mean? OEM is better than repop ACDelco?

Al Sanchez

I just spoke with my friend who rebuilt the transmission and he thinks he installed a shift kit in it.. Will a shift kit make it slam in gear like that? He also said to check the the idle may be to high.. Right now it set at 800 rpms does that sound right

Allan R

Good one! Agree it could be anything and you nailed the best way to find it.

Tony, that's not what Octania said. He said NEW is not the same as 'good'. You're sort of comparing apples to oranges. While everyone expects a new part to be 'good' or 'function properly', let's say that there are some that get past the quality control without being caught. Heck, even an NOS OEM u-joint could be subject to failure even though its never been installed.

EDIT: I think we're kind of jacking this thread. Maybe lets continue your issue on your thread and let the OP deal with his?

Al Sanchez

I'll double checked everything this weekend and hope it's an easy fix if not I'll just have to live with it till I can afford a 200r4 or a 700r and and some gears I just hope nothing breaks that clunk is scary

Allan R

Do you get the same heavy clunk going from Park to R, and from D to R?

Al Sanchez

The clunk happens on both but it's alot softer in reverse, reverse is more of a hard pull not a clunk like in drive, sometimes reverse goes in real smooth

Tony72Cutlass'S'

Mine sounds like someone is taking a rubber mallot to the floorboard..

Al Sanchez

Mine feels like I got rearended

Octania

No, I meant that brand new parts are not necessarily perfect. They can fail early. They can be installed poorly and fail- I recall having a UJ needle fall out during install and lie sideways and get crushed- I was young and inexperienced...

I have had brand new batteries die in a month, brand new spark plugs not work [on a 1-cylinder machine, you notice that right away].

The point was: "Don't assume it's ok just because it's new."

One of my Rules: always check first, the last thing "fixed". Verify a proper and viable repair.


"Mine feels like I got rearended"
====================
I ain't touching that one with a 10-ft Swede.
:-)

navvet

If it were a Plymouth you'd have to live with it!!!

Al Sanchez

I don't mind if I have to live with it just don't call my car a Plymouth lol.. Just kidding it shouldn't matter what make car you drive you should not have feel embarrassed to put it in drive in public dam clunk hope to get it sorted out soon...

pcard

Al - can you post a video with sound?

Al Sanchez

I'll try...