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Hey guys, wondering if someone might be able to help me troubleshoot this. Recently I installed some FRPP 3.73's as my pinion bearing was FUBAR when I bought my car. I opted to pick up gears with my rebuild kit. Well I marked the driveshaft and pinion flange so I could mate it up the same possition it came off.

Well fast forward to today.. I drove it out to Palm Springs (about 100 miles from me) to kind of break it in and also see how it drove. Noticed right away the improvement in the gears. However when I reached about 75-80 it vibrates like a loose wheel lug. I pulled off to check them and they're all tight.. Went ahead and torqued them a little more just in case. Vibration accures cruising, under throttle, and with clutch dissengaged. My only conclusion is maybe my driveshaft is off balance?

Second issue is a little harder to explain. When I got WOT from a dig 1st gear feels odd. Almost feels as though something is slipping. Clutch feels fine and doesn't create a burnt clutch smell, tires don't squeal, so don't think it's a traction issue (although it could be as I just have some cheap all seasons on it right now). Only other thing I could think is maybe belt slip? I have STeeda UDP's and a shorter belt to bypass the AC... This one could very well be in my head, but I wanted to see if maybe someone has encountered either of these issues
 

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did u take off ur drive shat? if so did u mark your drive shaft with the u joint?
 

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Do you have any pics of your gear mesh pattern?
 

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Discussion Starter #4
Yeah, I marked a line on the u-joint and pinion flange. No pics of the wear marks. Had a friend who used to build rearends at a local restoration shop help with shimming the carrier.
 

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I highly doubt it's the driveshaft not being installed right. I've taken many ds's off at work and never mark them, and never have vibration problems. now if your driveshaft fell or something and knocked off a weight then that's very possible.
 

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Discussion Starter #7
Haha it's weird drives super smooth until about 70+... Maybe a suspention issue?
 

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I know exactly what you're talking about with the 2nd issue. My car did the same thing, no squealing, clutch is fine. I think it had to have been the tires though. They car spin even slightly faster than the car is moving (not completely break loose) and not squeal. Haven't noticed it since I got my 315's :p
 

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i had the same issue with mine after installing the gears. unbolt the driveshaft from the pinion and rotate it 180* and bolt it back on. take it for a drive and try it
 

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Hey guys, wondering if someone might be able to help me troubleshoot this. Recently I installed some FRPP 3.73's as my pinion bearing was FUBAR when I bought my car. I opted to pick up gears with my rebuild kit. Well I marked the driveshaft and pinion flange so I could mate it up the same possition it came off.

Well fast forward to today.. I drove it out to Palm Springs (about 100 miles from me) to kind of break it in and also see how it drove. Noticed right away the improvement in the gears. However when I reached about 75-80 it vibrates like a loose wheel lug. I pulled off to check them and they're all tight.. Went ahead and torqued them a little more just in case. Vibration accures cruising, under throttle, and with clutch dissengaged. My only conclusion is maybe my driveshaft is off balance?

Second issue is a little harder to explain. When I got WOT from a dig 1st gear feels odd. Almost feels as though something is slipping. Clutch feels fine and doesn't create a burnt clutch smell, tires don't squeal, so don't think it's a traction issue (although it could be as I just have some cheap all seasons on it right now). Only other thing I could think is maybe belt slip? I have STeeda UDP's and a shorter belt to bypass the AC... This one could very well be in my head, but I wanted to see if maybe someone has encountered either of these issues
That something slipping may be the tires. :cool:
 

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Discussion Starter #12
I'll check out the driveshaft and let you know. I have a feeling the slipping is the tires, there's just no way for me to check being that i'm in the car haha. Appreciate all the help though guys.
 

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have you checked to see if your wheels are balanced? that's a very common issue for vibrations in higher speeds
 

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i've heard these same issues a few times and have the same after installing my 4.10's. i've also heard an aluminum driveshaft takes are of the vibration and better tires takes are of the "slipping". haven't tried either yet, but it's on my agenda for the near future.

on top of that, my 4.10's howell. i was told it's because of the aggressive cut angle on the teeth. anyone else with 4.10's experience that?
 

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I had the same issue with my DS. Vibration at a certain speed. Check tire balance, rotated pinion flange, replaced U-Joints, etc, etc... Put it up on jack stands and ran it through the gears and could feel the vibration in both the pumpkin and tranny. Bought an American Muscle FRPP Alum. DS and rides smooth as glass now.
 

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Discussion Starter #16
I thought about it being the tires, but why all of a sudden? Drove fine with the 3.27's. I'll check them all anyway though just to be on the safe side.

my 4.10's howell. i was told it's because of the aggressive cut angle on the teeth. anyone else with 4.10's experience that?
I've heard people having these issues from time to time. How's the wear pattern?
 

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I've also heard you need to go to aluminum drive shaft with a 4.10 to get rid of the vibration. Like the stock DS can't keep up or spin fast enought for that gear.
 

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...on top of that, my 4.10's howell. i was told it's because of the aggressive cut angle on the teeth. anyone else with 4.10's experience that?
Mine are quiet. Gear howl is usually caused by having the backlash set a little too tight.

I've also heard you need to go to aluminum drive shaft with a 4.10 to get rid of the vibration. Like the stock DS can't keep up or spin fast enought for that gear.
It isn't that it can't "keep up", it's that by reducing the mass of the driveshaft (by going to aluminum) without significantly changing its stiffness, you reduce the rotational force on the driveshaft, thereby reducing the vibration from the driveshaft.
 

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Mine are quiet. Gear howl is usually caused by having the backlash set a little too tight.
I also have 4:10's and mine are quiet. However, gear noise can occur even on a proper install (that doesn't mean you should be expecting obnoxious noises, in fact you should only be able to hear it if you are paying attention to it). Some brands like motive build their gears to be more durable and sacrifice comfort (comfort being the noise you hear). That's why I like FRPP, they're high quality and are the quietest gears in my opinion.

that being said I also agree the main cause of gear whine is caused by incorrect backlash. However, that doesn't mean you set the backlash incorrectly when you put everything back together. One of the problems could be you didn't have enough carrier preload. When you reach high speeds the diff starts to move around in the carrier because their isn't enough load on it and changes the backlash, which then causes the noise and vibration.

Obviously there is no way to measure carrier preload, but a general rule of thumb is that you should have to pound the diff back in the carrier with a mallet. If you're able to push it in by hand there isn't enough carrier preload. Don't be afraid to use a little force on it.
 
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