Are all 3.70 gears noisy?

[68EFIvert]

I have a rebuilt tracloc with Yukon 3.70 gears (new).  I have about 1000 on the car and notice that it is a little noisy.  When the car is under a load, even just driving at a constant speed the gears are noticably louder.  When the car is coasting there isn't a noise.  It this normal with 3.70 gears or is there an adjustment issue?  I've heard that Yukon gears can be a little louder than other brands but have no other experience with different brands of aftermarket gears.  What do you guys think?  I am tempted to take the pumpkin out and have it looked at but it has worked great for 1000 miles so it doesn't appear that the problem is big if one at all.

[66gt350]

When I was looking for new rear end gears to replace my 4:11's, I was told that some ratios are just inheritly noisy.  I can't remember (bad case of CRS), if I was looking at 3:70's or 3:89's, but I was told that they whine.  That's one reason I went with the 3:50's.  I've heard that Richmond gears are notorious for whining.  So, that could just be the way Yukon gears are...never used 'em.  Or it could be that the backlash is out of spec for Yukon gears...I've heard that each gear manufacturer is slightly different.  Have you yanked the pumpkin to change the gear lube?  I was told to do it between 500-1000 miles.  You could always check to see how everything is meshing up.

another solution is either crank up the stereo or uncork the exhaust! :lol

[camachinist]

If the gears make noise and it's static, meaning not changing in pitch or volume over time, then you own the noise. It'll be there forever, IME.

[buening]

Do they whine when decelerating?

[Fast68back]

My first set of 3.70's whined, the new set is night and day different, no noise at all.

[gotstang]

Sounds to me like they goofed the set-up. Both the "drive" and "coast" gear mesh patterns have to come out right if there is going to be any chance for it not to whine. We screwed up the "coast" side of the pattern on an old Chevy truck (several times in a row) and it did exactly what you're describing.

[silverblueBP]

My 3.70's didn't make any noise and the new Yukon 4.11's are quiet also.

[68EFIvert]

The whine is only when I am pressing the gas pedal and it is constant. It doesn't change volume or tone. There is no noise when coasting.  It looks like I will be pulling the pumpkin out just to make sure everythig is good.  :cry  I am so tired of doing or having things done twice. 

IIRC it takes 3 jugs of gear oil to fill the case.  Is that correct?  If I use synthetic do I still need friction modifier?  Is it worth it to use synthetic on a rear end?  What weight oil should I use?   

[PJ Moran]

If I use synthetic do I still need friction modifier?  Is it worth it to use synthetic on a rear end?  What weight oil should I use?   

When I installed my pumpkin, I wanted to use some of that case of synthetic gear lube I had on the shelf.  But the guy who built it said no synthetic.  I asked again to be sure and he again said no.  He is of the opinion that you will get chatter in "his" clutches if you run synthetic.  So, I put dino oil and modifier in.

I have no chatter, but can't say I would have with the synthetic.  Maybe it depends on the clutch material.  I suggest you contact the mfr of your "unit".

[66gt350]

I'm running synthetic in my rear...errr....9 inch....(man, what can I say without you perv taking it wrong!  LOL) differential.  but I'm not running a limited slip without clutches.  I'm running an Eaton Tru-Trac.  I've put about 500 miles since putting in the synthetic, and I haven't noticed any problems.

[68EFIvert]

I called the guy that built it for me.  He said that most aftermarket gears tend to make some noise compared to oe gearsets.  He said that depending on the ratio some will be worse than others.  He went on to tell me that the adjsutment to the gears can put the noise on either deceleration/acceleration/or try to get it neutral.  He tries to put it on the deceleration.  I evidently have one set up on acceleration.  He offered to swap me out a new center section at no cost or to swap out a new one with a different ratio for $100 and I pay 1/2 shipping.  I am tempted to take him up on the offer and go with some 3.50 gears that may be a bit quieter.  What do you guys think?

[silverblueBP]

I'm running synthetic in my rear...errr....9 inch....(man, what can I say without you perv taking it wrong!  LOL) differential.  but I'm not running a limited slip without clutches.  I'm running an Eaton Tru-Trac.  I've put about 500 miles since putting in the synthetic, and I haven't noticed any problems.

I've run Redline Shockproof since day one, no problems with a Tru-Trac!

[buening]

Darreld do you have the 0.5 or the 0.62 ratio in your 6th gear?  You may be getting to high of a gear with the 3.50s and may make 6th somewhat useless

[68EFIvert]

I don't have a .50 6th gear.  I thought it was .64 but could be wrong and it could be .62.  I am running about 2k rpm going 60 now so you may be right with the 3.50 gears.  I may just live with the noise and now screw with mailing the pumpkin back to PA just to find out the new one makes the same noise.  I'll have to sleep on this decision.  

My rear end guy  :lol did say not to run synthetic with a trac loc.  The clutches will chatter even if you put in the additive.  Standard gear oil is best and 3 jugs.

[tarafied1]

My rear end guy

I think of Beavis and Butt-head laughing at such a comment!

 :nta

[camachinist]

So glad I run a spool and 90W stinky LOL

OP, I'd just leave it. I ran 3.70's in my old street racer and they made a bit of noise too, audible when the car was corked up. Think of it like having a gear drive in the back....

[tarafied1]

So glad I run a spool and 90W stinky LOL

do you run the spool on the street?

[camachinist]

I did when I used to do that bad word LOL, back in the late 70's.

Substantially narrowed rear made 'driving' much easier. Once I moved to the track I never looked back. I still run all 'old' technology stuff, both on the street and at the track. I did put in one of those 'newfangled' aluminum radiators today. Didn't fit right so I drilled some holes in it. Reminded me of the old days LOL.

[66gt350]

Didn't fit right so I drilled some holes in it. Reminded me of the old days LOL.

If it was like the old days...shouldn't have you used duct tape and baling wire?  The REAL mans fix for everything!!!  :lol :lol

[camachinist]

LOL, I only did that at the track.... they don't call it racer tape and mechanic's wire for nothin.'

In the 'old days', we always accepted that a gear set might make some noise even if it was set up right. Things were a little more 'raw' back then. Now everything is so refined and proper and 'quiet'. Glad to see technology has advanced. However, even with those advances, one is still dealing with a specific design which is decades old. Expect some limitations.

[tarafied1]

I've always heard running a spool on the street can break axles. Ever had a problem with that?

[camachinist]

Still have the same narrowed 31 spline axles in the car that we had made back in the early 70's. If you're an old fart, you might remember 'Henry's' Axles in Anaheim.

Other than the slicks 'barking' when turning a corner, and the car being nearly impossible to 'push' when steered hard (like in the pits), I've never noted any issues. I never ran street tires so have no idea how that would work.

[68EFIvert]

Thanks for the input guys.  After sleeping on it I think I find other things to spend the money on.  I'll live with what I have for the time being.

[tarafied1]

The only reason I ask is I have a 4.11 traction-loc, a 3.73 open (thanks Rick) and 2.79 open. For the Power Tour I'm running the 2.79, but I would like to put in the 3.73's for normal use. I thought about a spool just cuz it's cheap but I don't want to break my stock 28 spline axles. I have considered swapping the gears from the 3.73 and 4.11 (4.11 is just too low with a 429) but I've never set-up a rear diff before. I guess either way I'd have to set it up...

[camachinist]

When I raced my street car (the one with the 3.70's/equa-loc that made noise) at the track, I threw in a spare differential that I had set up with 4.57's and a mini-spool (28 spline axles). Never had any issues with that one either. I used towing hubs (back then I flat-towed) to and from the track. It was a high 13 second car so relatively mild and I always ran street tires on it.