Transmission problem?

[JLPurcell]

1972 240Z production date 7/72

When I got the car back from restoration it had a clunking noise when backing up and wanted to pop out of gear. We thought that it related to the shifter.:bulb: I put a correct shift lever in the car with new bushings today and the problem is the same.:tapemouth Anyone had this problem. It is only there when backing and it sounds like a bad universal joint clunking.

[JLPurcell]

bump this thread

[djwarner]

When I bought my Series I with automatic, it had a bad clunk when shifting into reverse and when going back into drive. The PO thought it was a bad universal joint but it turned out to be a bad differential front mount. Overtime the rubber separates from the mount hardware but is held inplace by weight.

Two other things to inspect is loose nuts at the Ujoints and the amount of backlash in the differential.

Jumping out of gear may very well be separate adjustment problem or it may hint at rear transmission mount bracket problem.

[240260280z]

I rebuilt a series-1 4-speed for a resto. I had to grind some of the ball and spring mechanism to make it even go into reverse. This was part of the mechanism to prevent accidentally shifting into reverse. I am not sure why it needed this but it did. Aging would usually weaken parts over time so I was stumped.

You can see some of it here: Post #3 Photo 5: http://www.classiczcars.com/forums/thread42884.html

[JLPurcell]

When I bought my Series I with automatic, it had a bad clunk when shifting into reverse and when going back into drive. The PO thought it was a bad universal joint but it turned out to be a bad differential front mount. Overtime the rubber separates from the mount hardware but is held inplace by weight.

Two other things to inspect is loose nuts at the Ujoints and the amount of backlash in the differential.

Jumping out of gear may very well be separate adjustment problem or it may hint at rear transmission mount bracket problem.

All of the mounts, universals etc... should be new after a complete restoration at Classic Datsun Motorsports (rebuilt transmission and differential) but I will take a look. The clunking is only in reverse and is speed relevant (the faster you back up the faster the clunking). It can be felt through the shift lever but not when you lay your hand on the drive shaft (console and boot out).

[240260280z]

There was also a recent post about the clunk from slightly loose differential bolts/studs where it fastens to the moustache bar. I think Guy (Diseazd) found it.

[JLPurcell]

There was also a recent post about the clunk from slightly loose differential bolts/studs where it fastens to the moustache bar. I think Guy (Diseazd) found it.

I will try to check that out. Only in reverse?

[72 OJ]

This was my clonking noise only did it on reverse and was driving me nuts

Edited November 4, 2012 by 72 OJ

[JLPurcell]

This was my clonking noise [ATTACH=CONFIG]57709[/ATTACH] and the remedy [ATTACH=CONFIG]57711[/ATTACH] only did it on reverse and was driving me nuts

OJ,

It looks like yours would be a one clunk as the part moved and until next reverse no problem. My clunking is "rotational" it clunks repeatedly and in direct relevance to the speed you are backing. Are we talking the same clunking?

[72 OJ]

OJ,

It looks like yours would be a one clunk as the part moved and until next reverse no problem. My clunking is "rotational" it clunks repeatedly and in direct relevance to the speed you are backing. Are we talking the same clunking?

Mine was more acute on reverse and if I hammer her , the clonk was there, after the magical weld no more clonk and I drive her hard at times, she likes it and she was overbuilt to take it . Metal fatigue , that mount is 40 yrs old ( well most of it , there was a mod made for the Q45 diff) , I have secure a spare just in case

Edited November 4, 2012 by 72 OJ

[Mike]

All of the mounts, universals etc... should be new after a complete restoration at Classic Datsun Motorsports (rebuilt transmission and differential) but I will take a look. The clunking is only in reverse and is speed relevant (the faster you back up the faster the clunking). It can be felt through the shift lever but not when you lay your hand on the drive shaft (console and boot out).

Jerry, sounds a lot like something in the transmission to me. Did you inspect all of the gears or have the transmission rebuilt?

m

[Arne]

Jerry, a speed-related rotational clunking noise only in reverse almost has to be related to the reverse gears themselves. Any other source should have a matching noise going forward. As I sit here envisioning the parts that move only in reverse, I can't think of any other source. I fear the transmission needs to be torn back down.