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Grinding Noise in Reverse When Cold

2K views 15 replies 4 participants last post by  aldersonfilm 
#1 ·
Got a 98 with the 32RH 3 speed auto tranny, and it's beginning to act up. When the jeep is cold, if I throw it into reverse, there is a clearly audible grinding/rattling/buzzing. Sounds a bit like stones being vibrated inside a tin can. The noise will eventually fade away after about a minute or so and can't be reproduced after the jeep is warm. It appears to only be in reverse and it does not matter whether or not the jeep is moving.
I very recently did a Ford 8.8 swap, along with an SYE kit and new driveshaft. Since then, I have noticed quite a bit of vibration in the cab. The tranny also has a lot of gear whine, in all gears, but I'm not sure if that's normal for the 32RH. Anybody got any good suggestions on where to start? Fluid level and color look normal.
 
#4 ·
From the ECGS FAQ section, **** As with any custom suspension and axle packages we cannot guarantee that you will not need adjustable Uppers and a trac bar to completely center and get your pinion angle perfect. Every suspension system is different, however we make every feasible effort to make these bolt in to complete stock components or aftermarket parts***, http://eastcoastgearsupply.com/ft-379-ford-8-8-jeep-bolt-in-axle.html#q2016 so I would speculate that your pinon angle might be high or low which is causing your vibrations. Post a couple side view pics of your DS & pinon, it will be easier for everyone to see what you're working with.
Another thing to try is remove the rear DS and go for a drive. If the vibrations are gone then the problem is most likely with the pinon angle
 
#5 ·
Felt like an idiot today when I discovered that the rattling sound was in fact loose exhaust bolts at the donut where the header meets the pipe. However, that obviously didn't solve the vibration issues.

Good idea BM3, I'll try disconnecting the DS and taking it for a spin. I do think I'm going to need upper control arms no matter what, however, I don't know the procedure for adjusting and measuring the pinion angle. I know I adjust the upper arms to change the angle, but how do I measure it to know when it's right? The pinion angle should be pretty close, as it came from the shop, set, but will I need to relocate mounting points for anything like the shocks or springs?
 
#7 ·
#8 ·
Alright so went and got myself and angle finder and crawled under the jeep to get some numbers. I have an SYE, so my pinion angle should be the same as my driveshaft angle, however, the pinion is 4 degrees lower on both the front and rear driveshafts. Would this be enough to cause vibes? I'm assuming it could be with the compound angle on my 8.8. With such a small adjustment needed, could I get away with just a couple washers on the transfer case skid? Or cam bolts? The write up for adjusting the arms looks hugely complicated. I was under the impression one could simply tighten or loosen the nut on the arms to extend or shorten them and change the angle.
 
#9 ·
IIRC I think mine is set 1-2° lower then the DS... Yes you could add a couple washers to drop the transfer case skid to get what you need.
How i did my control arms, Lower ones I blocked the wheels, removed one arm set the length of the new one to match, installed the new one, repeat for other side.
On the uppers, I loosened the lower bolts, removed the upper bolts & arms. Place jack under pumpkin snout, lift as needed to get proper angle, install new arms, hand tighten bolts. Lower jack, check angle, repeat as needed to get what you want. Torque all bolts for upper & lower arms. Take for test drive, redo if still having vibes.
I never bothered to do anything to the front since it isn't affected by the sye & 8.8
 
#10 ·
Got it. The one thing I'm confused on is why I need both adjustable uppers and lowers. Which one would be better to get first? It sounds like people are pretty divided on this, and I'm not sure which is right. In my case, with my pinion angle too low, uppers seem like the obvious choice as I would have to shorten lowers, pulling them into the fenders. I may need to adjust the front as well, because I had a transfer case drop before installed the SYE and 8.8, so the vibes may actually be from the front.
 
#11 ·
Got it. The one thing I'm confused on is why I need both adjustable uppers and lowers. Which one would be better to get first? It sounds like people are pretty divided on this, and I'm not sure which is right. In my case, with my pinion angle too low, uppers seem like the obvious choice as I would have to shorten lowers, pulling them into the fenders. I may need to adjust the front as well, because I had a transfer case drop before installed the SYE and 8.8, so the vibes may actually be from the front.
Both... HTH
 
#16 ·
Got enough washers to drop the transfer case enough to get the angle of the rear driveshaft within 3 degrees. Still off, but it was closer. Honestly, didn't seem to make a huge difference. So then I disconnected the rear driveshaft entirely and tried driving around the block. Also didn't seem to help much. I did notice that the vibration seems to be most prevalent on acceleration. Didn't get the jeep up to highway speed, so I'll have to try that tomorrow, along with removing the from driveshaft.
 
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