FRPP 3.73 Gears..Two Thumbs Way UP!!

[rude_life]

OK just an update...I installed my new 3.73 gears and new diff. and pinion bearings and new trak-lok rebuild on saturday. After i installed the gears, trak-lok, and new bearings in my diff, i was having some funky sounds in cornering, but 1/2 an hour after driving it, All the sounds went away in the cornering and theres no whining or anything of that sort and I did put the friction modifier in, but only the little bottle which came which the TRak-Lok rebuild kit..Is that enough??? As for the shim on the pinion, we started off with a .030" shim and It was a damn good guess as the factory shim was .028..After a little assembly, we measured the backlash in about 6-7 differents places with a very nice magnetic base dial indicator and came up with .012" of backlash. PERFECT. Just to say, if you dont have gears in your car...BY ALL MEANS, GET A SET OF 3.73's. Oh my gosh ive just fallen in love with my car all over again. I am HIGHLY satisfied. Its just so much fun to drive my car now i love it. A point of concern though..And a question to anybody who has installed their own gears: Remember when you have to torque the pinion nut to like 16-20 LBS which is what we went with beacuse of the new bearings installed....Well that makes everything back there really tight. Now that i have the car back on the road, i can notice how tight it is...You know how at a stop light when you're in neutral with no brake..If the street is at all not level, you will roll forward?? Well im not rolling forward and i can actually feel the drag on my rear end while im driving. How long does it take this to loosen up? Is this normal? Now for the other problem..When im on the highway and id assume about over 80-85 MPH, I now get a horrible vibration after the gear swap. Felt and audible. It rattles so bad my shift knob feels like its going to rattle off. When i push the clutch in or put in neutral at the same speed, it doesent help at all. What can i do about this? Any tips?


Thank you very much,


Kris

 

[HISSIN50]

Glad to hear you like it, Kris.

Do you have the stock DS? With gears you are closer to its critical speed. A dynamic balance or alum DS might cure the vibes (assuming U-joints etc are all good to go).

Did you pack the TL tight?

Good luck.

 

[rude_life]

Yeah im pretty sure we packed the trak lok tight...But i dont think the driveshaft is the problem because i get the vibration just the same if i put it in neutral at high speed

 

[hotrodnut]

. A point of concern though..And a question to anybody who has installed their own gears: Remember when you have to torque the pinion nut to like 16-20 LBS which is what we went with beacuse of the new bearings installed....Well that makes everything back there really tight.
Kris

Is this inch pounds or foot pounds you set the pinion pre-load to? Did you do it with the ring gear out?

The viabration may be the drive shaft needing to be rotated 90 or 180 degrees. Try doing that and see if goes away before doing anything else.

 

[94GTLaserRC]

Ive always said of ALL the mods I have done, the best SOTP feeling aside from when the Vortech went in was when my gears went in...Got them in 1996 and have never looked back.
RC

 

[haulbalz]

when i put my aluminum drive shaft in it stopeed all my vibrations

 

[Venom351R]

I agree w/ Rob, aside from the power adder the gears were the best kick in the ass feeling for the car. I kinda did mine back asswards though. I had the supercharger and the AL driveshaft before I had gears. I put 3.55's and after that it made getting the blower so much more worth it.

 

[CManT1914]

Yeah im pretty sure we packed the trak lok tight...But i dont think the driveshaft is the problem because i get the vibration just the same if i put it in neutral at high speed

Your DS still spins though even when you have the clutch in. If the wheels are turning, so is the DS.

 

[rude_life]

That was ft lbs of torque and that was with the ring gear in

 

[final5-0]

Did you put your drive shaft back on exactaly like it came off to keep the balance the same?

Later
Grady

 

[AUcobra94]

. You know how at a stop light when you're in neutral with no brake..If the street is at all not level, you will roll forward?? Well im not rolling forward and i can actually feel the drag on my rear end while im driving. How long does it take this to loosen up? Is this normal?
Kris

I dont think its normal. I had gears put in my car and it never felt like a drag on the rearend. I have never heard of a gear change doing that. I would be more worried about that then the vibration.

 

[GRGT1994]

The pinion preload is supposed to be measured without the carrier in place. With it in place, it should take more force to turn the pinion (giving you an inaccurate preload measurement). But most importantly, it is measured in inch pounds, not foot pounds. It takes well over 130 foot pounds of force tightening the pinion nut down to crush the crush sleeve down to the 20 to 26 inch pound spec.

It sounds like you might have overtightened the pinion nut. Based on the drag and vibration you are talking about, I would suspect overtightening. I would stop driving it immediately (if you think this is the issue). And open the rear end back up.

You should pull the axels, carrier and driveshaft. Then remove and replace the crush sleeve. And tighten back to spec.

I think it is important to make sure the drive shaft is mounted in the same orientation to the pinion flang as it was originally. But that really does not sound like it's your issue here.

Keep in mind that ripping everything back out and resetting the crush collar will not be nearly as hard or time consuming as all the other work you just did. So hang in there.

Good luck.

 

[94-302-vert]

Ft Lbs not In-Lbs... IF you are sure about that look into it as I am 95% sure it should be in-lbs... You should be able to rotate it by hand pretty easily... I think you may have orver tourqued and now you wasted a crush sleeve and possibly one or both pinion bearings. I would re-verify this before you end up in the position I am at.. 10 weeks, ony 2000 miles and not trusting it yet because i do not know if the bad wear pattern from the first install or new problems are giving me my headache...

Chris

 

[89MustangGX]

I also vote for the DS in the vibration problem.

It worries me a little that it made noise and then went away -- that doesn't sound right. Could also be an indicator of the other problems being talked about here.

 

[hotrodnut]

That was ft lbs of torque and that was with the ring gear in

Yep, as GRGT1994 and 94-302-vert said, the torque is to be at an inch pound setting and as GRGT1994 said, without the carrier assembly installed, their suggestions should not be taken lightly.

 

[rude_life]

OK guys heres the scoop. When i installed the gears i accidentally torqued down the pinion nut in ft lbs instead of inch lbs .. When i tightened the pinion nut down i did so with the diff assembly out of the housing, so at least that was right. Went out and bought a new pinion nut and crush sleeve today along with some more gear oil and limited slip additive. I took everything back apart..Thankfully the pinion bearing was new and was not damaged, warped or discolored at all, neither was the pinion bearing race. So i went ahead and reassembled everything, torqued the pinion nut to 22 inch lbs, measured the backlash in about 5 different places and came up with .014" of backlash. Evrything is back together now and the car is running sweet. Needless to say the rear end doesent feel tight anymore at all. I have learned my lesson.

A BIG THANKS to everyone who offered advice and helped me realize i had made a mistake before things got drastic

 

[Methodical]

when i put my aluminum drive shaft in it stopeed all my vibrations

Ditto. Did the adjustments you made fix the vibrations you had. If yes, forget the rest of this message. If no, then read on. You can get vibrations even in neutral if the DS is bad because it is still spinning. As the post above stated try rotating your drive shaft. Better yet take it to a drive shaft shop and have them check the balance. Or even better yet, just get the aluminum driveshaft. Peace. The 3.73s are the way to go. Not too much (4,10) and Not too little (3.55).

 

[GRGT1994]

Rock on!

 

[rude_life]

You know what was funny though...After we put everything together the first time and it was really tight, we thought it was normal for preload on the bearings and we thought it would loosen up. As i drove around and burned off 3/4 of a tank, I was like damn im getting horrible gas mileage and every time i shift gears, i can feel the drag on the rear end. So i kept saying, you know my gas mileage is real crappy and i think its because the rear end is so tight..Everyone kept saying, "oh you switched to a lower gear ratio, your gas mileage is going to be crappy now". I keep saying no, it shouldnt be that crappy, if anything maybe a little bit better because i get out of the hole and up to speed a lot faster with the new gears. Well i guess i was right because the gas mileage has improved dramatically since last night.

 

[89MustangGX]

Nice job.