What grindes my gears!

Hear goes. I have a 91 XJ 4.0 242 sitting on 31's A 3.5 re super flex with teraflex shackles in the rear. Just the straight ones. I have the RE hack and tap with a TW Driveshaft going to a 8.8. Hears my problem.

I got 4:10 Superior gears and had them in staled by a local mechanic and ever since then i get nasty vibrations around 50mph. This only started after the gears were installed and its driving my nuckin futs! Every time i bering it back to the mechanic he give me the run around and blames the transfer case bearings as well as hub bearings and other stuff.

Now before i had the gears down every thing was fine. No vibrations at all. I did a test the other day and pulled out the rear drive shaft put it in 4wd and went for a spin. Guess what, no vibrations! I re checked the pinion angle and every thing was still ok. After i told him about the test i did he blamed the DS. I had that check and it was fine.

So the point is WTF did this guy do to my gears?
The pinion bearing is now humming along, wile on the gas.

I scersouly think he Fed something up in there and dose'nt want to fix it.

can any one help or offer advice?

Im desprate here and i don't have the funds to re do things again.

Take a look in your local chapter here and see if there's anyone near by where you live that could check the gears for you. Sounds like he didn't set the backlash right or put enough shims on the pinion. One of the guys around you that has the tools to install gears can prolly pop the cover and check them for you so you have a definate answer as to what happened.

how did you check the driveshaft?

Do you have a lift?

an SYE?

generally gears dont cause vibrations... I'd be very suspicious of the rear driveshaft - even if the angles are what they're supposed to be...

sounds like a pinion u-joint to me...

dave92cherokee said:

Take a look in your local chapter here and see if there's anyone near by where you live that could check the gears for you. Sounds like he didn't set the backlash right or put enough shims on the pinion. One of the guys around you that has the tools to install gears can prolly pop the cover and check them for you so you have a definate answer as to what happened.

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Thanks for the advice. I live on Long Island NY and there not much 4 wheeling here so i doubt theres a local chapter close but im sure i know some one who knows some one who could do it. I've been hearing lots of things about what could be wrong and im hearing a lot about the shims and backlash but who knows. The mechanics last scapegoat were some loud transfer case bearings.

XJ_ranger said:

how did you check the driveshaft?

Do you have a lift?

an SYE?

generally gears dont cause vibrations... I'd be very suspicious of the rear driveshaft - even if the angles are what they're supposed to be...

sounds like a pinion u-joint to me...

Click to expand...

I check the pinion angle with 2 different angle finders and with some else checking it as well. Just to make sure. If theres a better way to do it im all ears.

Yes As I said it's a 3.5 RE super Flex. and yes i have a SYE and a tom woods custom d/s.

I check the u-joints and replaced one then I had it checked for balance at a local truck shop and was told it was fine.

I has to be something with the gears, thats the only thing that changed unless he hit the driveshaft with a hammer?

Did you put the gears and the 8.8 in at the same time?

RCP Phx said:

Did you put the gears and the 8.8 in at the same time?

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No I did not. I bought the 8.8 with 3:55 to match my dana 30, that was about a year ago. When I did the axel swap I instaled the RE hack and tap SYE and ordered a Tom Woods drive shaft.

Every thing was running good, no humming and no vibes. Then I brought the jeep to this Mechanic with the gears and bearings and it vibrates when I drive.

I got vibes after my gears were installed. It happened that the H&T got sloppy on the TC output shaft. Changed to a AA SYE and all is well.

Post up in the NAC chapter there's prolly a bunch of people that live in NY and some maybe close to you. When you bought the gears did you buy an install kit or overhaul kit or anything at the same time? If not then he probably reused the original shims and guessed everything would be good. Also not sure if it would cause an issue like this but did you regear the front at the same time?

have the gears checked out. bottom line, he fawked them up.

another thing that could have happened is that he could have bent/broken/damaged the 1310 flange adapter or whatever you're using on the 8.8

where in new york? theres some gear gurus in my local club

long island

jeepcomj said:

have the gears checked out. bottom line, he fawked them up.

another thing that could have happened is that he could have bent/broken/damaged the 1310 flange adapter or whatever you're using on the 8.8

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Or the presure spring on the back side of the pinion seal fell out and got smashed between the yoke and the bearing.

I had the same problem. It ended up being the drive shaft. Got a quality shaft built and now there gone. I guess it was because the shaft was spinning faster after the gears and it just became noticeable. Just an idea.

As live24wheel mentioned, keep in mind whenever you go to a deeper gearing, your driveshaft has to spin faster at any given speed. If you have a worn u-joint, bearing, bad pinion angle, etc... it's much more likely to show up after a regear.

You said you checked the angles with an angle finder, but didn't mention what they are? With an SYE, your pinion should point about 2* below the DS.

Also, as XJ Ranger asked, how did you check the driveshaft? This isn't referring to the angles, but the balance.

Now as far as any pinion or gear noise, yes, you can blame the installer.

TRAILREADYXJ said:

As live24wheel mentioned, keep in mind whenever you go to a deeper gearing, your driveshaft has to spin faster at any given speed. If you have a worn u-joint, bearing, bad pinion angle, etc... it's much more likely to show up after a regear.

You said you checked the angles with an angle finder, but didn't mention what they are? With an SYE, your pinion should point about 2* below the DS.

Also, as XJ Ranger asked, how did you check the driveshaft? This isn't referring to the angles, but the balance.

Now as far as any pinion or gear noise, yes, you can blame the installer.

Click to expand...

I set my pinion angle at 2* below the output shaft with double cardan driveshaft I had built. no vibes, no problems. from what I've been told, you set pinion angle compared to output angle, not as compared to driveshaft angle.

jeepcomj said:

I set my pinion angle at 2* below the output shaft with double cardan driveshaft I had built. no vibes, no problems. from what I've been told, you set pinion angle compared to output angle, not as compared to driveshaft angle.

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That's correct if you don't have an SYE, but with the SYE and CV shaft, you go by the DS angle.

EDIT: Just noticed you have an MJ, and while it sounds like your angles are off, you probably don't feel vibes and such since you have a longer rear DS and are less prone to vibes in the first place.

dave92cherokee said:

Post up in the NAC chapter there's prolly a bunch of people that live in NY and some maybe close to you. When you bought the gears did you buy an install kit or overhaul kit or anything at the same time? If not then he probably reused the original shims and guessed everything would be good. Also not sure if it would cause an issue like this but did you regear the front at the same time?

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I think it was an over haul kit, believe it came with shims. Now that you mention it I think he did say something about re-using an old part. I think it was a bolt that held the ring gear to the carrier, im not sure. Both front and rear were done at the same time.

TRAILREADYXJ said:

As live24wheel mentioned, keep in mind whenever you go to a deeper gearing, your driveshaft has to spin faster at any given speed. If you have a worn u-joint, bearing, bad pinion angle, etc... it's much more likely to show up after a regear.

You said you checked the angles with an angle finder, but didn't mention what they are? With an SYE, your pinion should point about 2* below the DS.

Also, as XJ Ranger asked, how did you check the driveshaft? This isn't referring to the angles, but the balance.

Now as far as any pinion or gear noise, yes, you can blame the installer.

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As far as the drive shaft goes, its a Tom Woods double cardon with the slipyoke . Its been in the jeep for maybe 9 months and I replaced one bad u-joint.

I had the shaft checked for balance at a local big rig truck shop with their own axel and d/s shop. This guy told me he spun it up to 3500rpm, as fast as the machine would go and it was flat. No problems, and this was with the flange adaptor for the 8.8.

Now for the angles, I don't know off hand but I do know that they are only 2 degrees from one another

Any way Im going to bring it a diffrent mechanic for a second opinion and see what happens. I just want it fixed and drive it again.

and wheel again, of course

Thanks again every one for all your input and help, happy halloween!

Want to completely rule out the rear drive shaft?

Remove it, put it in four wheel drive part time, and go for a drive.

What happens?

just another thing to try on mine the drive shaft i bought offline was built wrong and the ears wernt inline so it made it vibrate. so i straitened it and had alocal shop balance it solved the problem for me

GSequoia said:

Want to completely rule out the rear drive shaft?

Remove it, put it in four wheel drive part time, and go for a drive.

What happens?

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It goes away! Is it me or is no one reading the whole thread before posting? I swear this is the 3rd or 4th time some one has asked a question that has already been answered. (sorry to be off topic).

But any who,
I'd say have some one else check the backlash, wear pattern, and bearing pre-load.