Backlash in the drivetrain
#1
Backlash in the drivetrain
This one has me scratching my head so I thought I would ask for advice....
When traveling down the road and applying/unapplying throttle i can hear and feel a "clunk" that seems to be coming from the rear end.
All diff and transmission mounts are good. Fluid levels are good. U-joints are good. Pinion bearings good.
When under the car with the e-brake applied, twisting the driveshaft does not produce the clunk....however when the e-brake is released the clunk can be replicated and seems to come out of the diff. The clunk can also be made by grabbing either rear wheel while it's up in the air and turning it forward/reverse rapidly.
What inside of the diff could have this slack in it? is it possible the transmission has the slack and is transmitting it though the driveshaft to the rear end?
When traveling down the road and applying/unapplying throttle i can hear and feel a "clunk" that seems to be coming from the rear end.
All diff and transmission mounts are good. Fluid levels are good. U-joints are good. Pinion bearings good.
When under the car with the e-brake applied, twisting the driveshaft does not produce the clunk....however when the e-brake is released the clunk can be replicated and seems to come out of the diff. The clunk can also be made by grabbing either rear wheel while it's up in the air and turning it forward/reverse rapidly.
What inside of the diff could have this slack in it? is it possible the transmission has the slack and is transmitting it though the driveshaft to the rear end?
#2
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Been there, done that.
I am betting it is the forward differential mount. The center, rubber section fails in shear along a vertical plane. Without stress on it, the two sheared parts line up and it's hard to see the failure. Push up and down on the front end of the differential, and you should see the movement between the two failed parts of the mount.
I am betting it is the forward differential mount. The center, rubber section fails in shear along a vertical plane. Without stress on it, the two sheared parts line up and it's hard to see the failure. Push up and down on the front end of the differential, and you should see the movement between the two failed parts of the mount.
#4
So he's obviously saying his mounts are good, well it doesn't hurt to do the check by pushing up on the front of the diff the next time your under the car. But other than that possibility I'm not all that sure either, however I have a similar problem and I have mmr-direct diff mounts with a stock front mount, and I still have some kinda slack issue.
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#10
S5 T2
iTrader: (6)
Wow, that seems excessive... If it were me, I'd pull the diff cover off, and visually inspect for whats causing the noise. If I had to guess, I'd say either the ring gear or pinion has moved slightly out of tolerance, or theres some heavy wear on one of the two.... or even both. The crappy thing is that rebuilding diffs isn't what I would call a "fun" weekend project....
Any leaks around the diff?
The break calipers arent' moving?
Any leaks around the diff?
The break calipers arent' moving?
#12
RIP Mark
iTrader: (2)
Wow, that seems excessive... If it were me, I'd pull the diff cover off, and visually inspect for whats causing the noise. If I had to guess, I'd say either the ring gear or pinion has moved slightly out of tolerance, or theres some heavy wear on one of the two.... or even both. The crappy thing is that rebuilding diffs isn't what I would call a "fun" weekend project....
Any leaks around the diff?
The break calipers arent' moving?
Any leaks around the diff?
The break calipers arent' moving?
#15
Banned. I got OWNED!!!
Your answer is in your thread title. The diff should be set to .005" backlash. @ .020" the dif will sound like its about to EXPLODE. Think about that, a difference of 15 thousandths of an inch is the difference between brand ******* new, and sounding like someone tossed a handfull of gravel in the rear end.
There is no cover to pop off, you're thinking of solid axles like the rustangs and suck.
There is no cover to pop off, you're thinking of solid axles like the rustangs and suck.
#19
Banned. I got OWNED!!!
The answer is hardly any.
There's really nothing left for you to do, you have two choices
1) Deal with it
2) Drop the carrier and rebuild it
Rebuilding a rear end is not that hard, the hardest part will be getting the subframe off and back on. Rebuilding the diff is pretty easy, just time consuming, VERY time consuming. Triple check everything because you only get one chance before it gets FUBAR.
#20
S5 T2
iTrader: (6)
My apologies, I know lot's about diff's coming from building Jeeps from the ground up, I just didn't realize that the RX7 diff didn't have a cover. I've only owned mine for a few weeks afterall.
How do you set the pre-load in the pinion on an RX7? Does it use a crush sleeve, or shims?
I do agree with Titanium, although I have to disagree with gear jobs being easy. If you've done it before, yes, it's pretty straight forward. If it's your first time, give yourself a weekend or two to do it. And you HAVE to have the proper tools to do it with, there's no way to take shortcuts. The beauty of it is that diff rebuilds can be rather inexpensive if you do it yourself. Shops make tons of money on the labor for this type of job.
How do you set the pre-load in the pinion on an RX7? Does it use a crush sleeve, or shims?
I do agree with Titanium, although I have to disagree with gear jobs being easy. If you've done it before, yes, it's pretty straight forward. If it's your first time, give yourself a weekend or two to do it. And you HAVE to have the proper tools to do it with, there's no way to take shortcuts. The beauty of it is that diff rebuilds can be rather inexpensive if you do it yourself. Shops make tons of money on the labor for this type of job.
#22
Banned. I got OWNED!!!
My apologies, I know lot's about diff's coming from building Jeeps from the ground up, I just didn't realize that the RX7 diff didn't have a cover. I've only owned mine for a few weeks afterall.
How do you set the pre-load in the pinion on an RX7? Does it use a crush sleeve, or shims?
How do you set the pre-load in the pinion on an RX7? Does it use a crush sleeve, or shims?
I do agree with Titanium, although I have to disagree with gear jobs being easy. If you've done it before, yes, it's pretty straight forward. If it's your first time, give yourself a weekend or two to do it. And you HAVE to have the proper tools to do it with, there's no way to take shortcuts. The beauty of it is that diff rebuilds can be rather inexpensive if you do it yourself. Shops make tons of money on the labor for this type of job.
And just becuase backlash is written in here so many times and I'm willing to bet it'll show up on a few searches, here are some things to look for when setting up a diff -
Put the pinion on a set of Vblocks and check it for round. I didn't do this with one diff and it ate the gears in a matter of a few hundred miles.
If you're setting backlash and it diff likes to lock up as in not turn, check the ring for step wear. The pinion can jam in the unworn section of the ring gear and screw you.
That mile long pinion and moreso the multiple bearings IMHO is one of the reason these rears are so damn strong.
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