"Klunk" when shifting to R

[Deleted member 1959]

I think I remembered to tighten the lugnuts will check...
So is it just a matter of ordering a new crosspin or are there other parts that probably needs changing while the diff is apart ? The car has done 51500 Mi.
I usually order from Rockauto, but I can´t find a crosspin on its own for my car in their catalogue. Can you tell me where to order the right parts ?
I have a friend who id travelling to Denmark on the 8th og August. It would be sweet if I could get the parts to him before then.

 

[volare 1977]

I would not order a cross pin just yet. I would take the cover off and inspect. The case most likely would be damaged around where the cross pin goes in. The pin would not fix the problem if that is the case. The pin comes out pretty easy after you remove the locking pin. As I said the rear would have to been abused for that to happen which sounds like that is not the case. Inspect first. Unfortunately the video doesn`t show a sure grip unit.

 

[volare 1977]

Also, If the rear axle is ok then the clunk could be caused by the low/ reverse band adjustment in the trans as you originally questioned.

 

[Deleted member 1959]

Great video I do suspect the low/reverse band still, since there is no clunk when switching to D and no noise from the rear when driving.

 

[BudW]

On most (automatic) Mopar vehicles, there is almost always a clunk that sounds like coming from center of car, when vehicle is shifted from drive to reverse. The main reason for this is the way the transmission sun gear shell looks (acts like an amplifier of metallic clunk noise).

Also, with the several parts inside of transmission, propeller shaft and differential, there is several items that has a little slack in them. A lot of “little slacks” equals to a lot of slack. What ends up happening is the front clutch drum where it splines into the big end of the sun gear shell – with all that accumulated slack the aluminum planetary gear slams into the shell – accentuated by fact these parts are changing rotation direction – the slamming parts rings that shell and sounds like a clunk.
In most cases, the clunk is not anything to worry about.

inner and outer picture of sun gear shell

Front clutch drum (and rear side of front pump).

As splined together


With that said, there are cases where the clunk is not normal.
One of which is loose U-joints (which I don’t think is the case here), a cracked or broken flexplate (again, I don’t think is an issue here) or internal differential failure (again, I don’t think is an issue here, less so on cars with limited slip differential).

If you had loose lug nuts – you would have other issues you would notice (like car feels like a wheel wanting to fall off, for example).

My recommendation is to give a slight pause when shifting from drive to reverse (or vice versa) so just let shifter sit in neutral for a second or so, before next position.
BudW

 

[Deleted member 1959]

Hi Bud
Thank for the - as always - very comprehensive and to-the-point explanation. I have bought some new U-joints and a gearbox mount already, but they did not cost much since I had a US work colleague bring them over for me.
I am happy that there is probably nothing wrong with my gearbox or diff, and I will just use the Neutral method from now on
Claus

 

[81ImpNC]

Make sure your idle isn't too high. People often let base idle drift up and it makes that noise louder. Most 904s have that noise. My car's base idle in drive should be 580RPM +- It has been up to 750RPM before.

 

[BudW]

Make sure your idle isn't too high. People often let base idle drift up and it makes that noise louder. . .

Good point!