3.91 gears help

[TheFlyingBananaSS]

Originally Posted by Moto-Mojo

What engine RPM do 3:91 gears put you at in an A6 at say, 75MPH? Thx. (in 6th gear)

I'm over 2000 at that speed.

[rontammy0]

Originally Posted by TheFlyingBananaSS

I'm over 2000 at that speed.

Yes 2200 at 70 mph.

[Moto-Mojo]

Thanks, boys. Did either of you go with a GM 1LE set of gears - assuming they are available? Just thinking OE would be best if possible.

[PepeLePew]

Originally Posted by Moto-Mojo

Thanks, boys. Did either of you go with a GM 1LE set of gears - assuming they are available? Just thinking OE would be best if possible.

I went with GM 1LE gears. I just had them installed yesterday and should be ready for pickup today so no seat time yet plus I need to go through the break in procedures before I get to enjoy them.

[Mr2Hard2See]

Originally Posted by Moto-Mojo

Thanks, boys. Did either of you go with a GM 1LE set of gears - assuming they are available? Just thinking OE would be best if possible.

Majority of the talk has been about GM parts

[Moto-Mojo]

Originally Posted by PepeLePew

I went with GM 1LE gears. I just had them installed yesterday and should be ready for pickup today so no seat time yet plus I need to go through the break in procedures before I get to enjoy them.

Interesting. Does the actual 1LE Camaro manual talk about a diff break-in procedure when you buy one? (maybe similar to the engine?) I'm coming around but old school enough that the 'ol "break 'em in how you're going to drive it" still rings in my ears!

[mbesman]

Could I ask how much it cost? I am about to get it done myself. Have GM dealer quote of 700 with recalibration and a local shop at 645 with calibration. I'm supplying parts and oil.

[PepeLePew]

Originally Posted by Moto-Mojo

Interesting. Does the actual 1LE Camaro manual talk about a diff break-in procedure when you buy one? (maybe similar to the engine?) I'm coming around but old school enough that the 'ol "break 'em in how you're going to drive it" still rings in my ears!

I read a lot about this and pnwdan gave some really good advice on how to break in new gears. As far as the need to break in gears in a new vehicle, I am still unsure as to why there aren't stringent guidelines and what the factory does differently for a new car. Maybe gears installed in new cars are properly lapped under force prior to installation. And maybe the GM gear kits are done the same way. I honestly don't know, but I am not willing to take the risk.

I did find though that new ring and pinion sets in general are lapped from the factory but not under the same loaded conditions created from driving (maybe this only applies to aftermarket gears).

This is what I found about why we need to break in a new ring and pinion.
When you do the correct heat cycles for a new ring and pinion, you are effectively making the gears stronger through proper "work hardening". Doing this properly is similar to the forging process and must be done without excessive heat. The teeth on new gears contain very small high spots that will be compacted into the face of the gear teeth. The additional friction of the new gears with these tiny high spots creates significantly more heat than gears that have been properly broken in. If close attention isn't paid to performing short heat cycles correctly, then gears can overheat and actually become softer, less durable and more prone to failure.

I just figure, why risk it?

[PepeLePew]

Correction.. it was acammer that gave me the advice on break-in in another thread. His advice is a little more conservative than the gear companies may say around the time needed for cool down while heat cycling. But this is what I'll be doing.

"There are a few key points on new gear break-in. Heat is the enemy - especially in those first hundred miles - those new gears heat up fast. The recommendation on a brand new set of gears is to try to get in several short (15-20 minute) heat cycles (completely cool after each for 2-3hrs). You want a minimum of three, and more like 4-5 if you can, and then you can start taking longer duration drives. All thought that 500 miles though you want to manage heat with some care - I would try to keep driving duration under an hour with plenty of time to cool after each drive. Some people might not be so meticulous about the heat cycles after the first 2-3, but I think it's real important.

Those first couple heat cycles you want to avoid steady highway cruising, you want a drive that varies the speed, has some deceleration zones, etc. You also want to avoid heavy load in those first 500 miles - resist the urge to bury the throttle and be nice to those gears. Once you've got 500 miles on drain and replace the fluid - it will have a pretty good amount of crude in it as those gear faces wear into each other, and it will have been exposed to some pretty serious heat on those first few drives.

Once the fluid is changed - send it. You can do your entire drive-line a big service by pre-loading if you're going to launch the car. I use the emergency brake at the drag strip to hold the car on the line, and right as the tree starts to drop I lightly drag the clutch so that all the slack in the drive-line is taken up before I start the launch."

[jokrz187]

...

[PepeLePew]

Originally Posted by mbesman

Could I ask how much it cost? I am about to get it done myself. Have GM dealer quote of 700 with recalibration and a local shop at 645 with calibration. I'm supplying parts and oil.

pnwdan and Mr2hard2see were able to save a bunch of money by piecing their kits together. They did a ring and pinion, new bearings, and an install kit for $300-$400. They both detailed the parts they ordered in a separate thread that I am having trouble laying eyes on right now. I think parts break down was about $230 for ring and pinion, $80 for both bearings, and $30 for the install kit with shims, marking compound, and seals (I couldnt find the install kit for that price). If you go that route, you may decide to replace the rear gasket and some of the "reusable" hardware that comes in the gear kit that GM sells for a little extra.

I wasn't as lucky (smart), and ended up going with the full kit for $510 and I added on the pinion bearings for another $80.

Install at about $700 seems standard in my research if you go to a speed shop or the dealer. pnwdan got a killer deal through a transmission shop and I want to say they charged him about $300 (going from memory) for the swap plus fluids.

[Moto-Mojo]

Well, this I do know. I built and rebuilt class 8 diffs for a few years in the 1980’s. Rockwell SQHD, front and rears all day long. EVERY one got a new gear set and immediately went into a truck hauling 80k lbs. We never once considered, advised or recommended a break in period. Those trucks hit the bricks. Maybe apples and oranges I know but how much more severe service can you get on a new gear set?

But you’re probably right. Not worth buying them twice. I’ll certainly ask me gear man what his experience has been.

[Mr2Hard2See]

I was told a 500 mile break in is good. First drive 15/20 miles for first heat cycle. Repeat that a 2nd time. Keep the speeds 60 mph and under with different driving conditions. 1500 miles change diff fluid again and enjoy.

[Mr2Hard2See]

Originally Posted by PepeLePew

pnwdan and Mr2hard2see were able to save a bunch of money by piecing their kits together. They did a ring and pinion, new bearings, and an install kit for $300-$400. They both detailed the parts they orderedin a separate thread that I am having trouble laying eyes on right now. I think parts break down was about $230 for ring and pinion, $80 for both bearings, and $30 for the install kit with shims, marking compound, and seals (I couldnt find the install kit for that price). If you go that route, you may decide to replace the rear gasket and some of the "reusable" hardware that comes in the gear kit that GM sells for a little extra.

I wasn't as lucky (smart), and ended up going with the full kit for $510 and I added on the pinion bearings for another $80.

Install at about $700 seems standard in my research if you go to a speed shop or the dealer. pnwdan got a killer deal through a transmission shop and I want to say they charged him about $300 (going from memory) for the swap plus fluids.

Originally Posted by pnwdan

I bought the gear set on Amazon for $260 (GM gears)
seems the price went up but this is how amazon is. It will prob go back down again
https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

I bought the pinion bearings on Amazon for $100
https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1
https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

I bought the Yukon Gear Minor install kit on Amazon for $30
This will go back up to full price an go back down again. Wait it out if the price goes up
https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1



and I paid $250 to have them installed

Shop around and find the best deal. You may save more than what you are on Ebay

Originally Posted by Mr2Hard2See

well guys I just bought all my parts on ebay. My parts total came out to $364.90 for everything above....I'm astatic because I just killed it deal wise. fellas you guys gave me the proper info and I utilized my shopping skills. This has to be the cheapest you can buy all of these brand new parts for.

gear set $271.44 10% discount=$246.54

s1392 rear pinion bearing $41.69 10% discount=$37.52

s1387 pinion inner bearing $55.74 10% discount=$50.17

Yukon Gear Minor install kit on Amazon for $30

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