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View Full Version : RB25 Rear end makes clunking noise


malemodel69
03-26-2010, 01:14 AM
Here is the deal:

Had the transmission rebuit in my S14 (rb25det with rb20 trans). Had a one piece drive shaft put in. Ever since, my car makes a "clunk" when shifting or when i let off the gas really quick and when i lightly tap the gas. Transmission is touching the firewall on the passangers side. Going to get under the car this weekend so if anyone can give me some pointers it would be appreciated. Thanks in advance.

Some specs if it helps:

S14 RB25DET/RB20 transmission
One piece steel driveshaft
R33 Crossmember with stock KA mounts (a dumbass did the swap - Chris Millano/Kregorian) :wtf:
ACT 6puck sprung clutch
New Diff bushings - ES polyutherane

fliprayzin240sx
03-26-2010, 04:27 AM
Well, if its touching anywhere, time to bang it out. Hopefully you have enough room to bang it out without dropping the damn tranny.

Also, you sure its not shitty subframe bushings? Oh yah, double check the tranny mount, maybe shits loose.

malemodel69
03-26-2010, 11:41 AM
Well, if its touching anywhere, time to bang it out. Hopefully you have enough room to bang it out without dropping the damn tranny.

Also, you sure its not shitty subframe bushings? Oh yah, double check the tranny mount, maybe shits loose.

Definitely banging the firewall out, even if it requires pulling the whole engine. Subframe bushings could be a problem as i might not have enough room to raise the car - damn jacks don't don't raise the car high enough, had to use wood blocks before :cry:
I will post the results tomorrow after banging the firewall out...

DJDANGER24
03-26-2010, 12:32 PM
i had the same problem in my hatch, but i had the RB25 motor and tranny with Mckinney mounts, my trans mount was a little loose.
it would make that clunk when i would let off sometimes or shift at low RPM's and "nudge" the gas....
also check the u-joints on the driveshaft.

s14sport
03-30-2010, 02:39 PM
also another thing to check out is the final gear in the diff.

with the car lifted in the rear and obviously e-brake off and out of gear rotate the driveshaft to see if there is any play.

if the driveshaft rotates some before hitting any resistance inside the diff then you have some play in the final gear.

1GayDrifter
03-31-2010, 12:47 AM
probably dont matter but since u have a one piece DS every time u give it gas the DS turn the diff right away and does make a little clunk since there is no rubber like in a stock DS to absorb some of that..

malemodel69
03-31-2010, 08:49 PM
So, i did lower the trans and took a few hits to the firewall. Didn't seem like i made any major progress but once i started driving i could not hear the clunk. I did fuck around and tried to replicate the noise, it worked a few times but now it does not happen in regular driving. I realized that I already have poly subframe bushings, they were dirty so I did not notice them last time i was fucking around under the car. Next project will be making an adapter plate to mate a z32 trans to the RB25, i'll see if my welding guru can help me out. If I ever develop the POS i'll definitely start selling the damn thing, RB25 transmissions are too expensive and why bother with the bellhousing swap when it could just mate? Anyone know if the striking rod would have any difference between those two - RB25/Z32 transmissions?

BTW, all of your input put some great ideas into my mind when working out the problem, thanks again. s14sport/1GayDrifter - I will check the driveshaft again this weekend, didn't have enough time on saturday...
Results will be posted for any other n00bs that run into the same problem.