The Official 1LE 3.91 gear swap thread - Page 7 - Camaro5 Chevy Camaro Forum / Camaro ZL1, SS and V6 Forums

blakjak55 · 04-01-2016, 07:49 PM

I replaced all mine when I did mine at 50k miles and some change. The carriers would have been fine except the races had some pitting and the inner pinion bearing sometimes will get the cage stretched during removal.

Up to you but the carriers and races should be just fine. Pinions I would replace both with new races.

frankwjr · 09-26-2017, 08:59 AM

Just finished up my 3.91 upgrade...replaced all bearings/races due to mileage(actually everything inside looked perfect!) so this was a bit more involved that just a gear swap...just want to add that even after all of the extra stuff I did, the ring and pinion went back in with factory shims and a .002 backlash and perfect pattern...freakin wild!

Also added a Ford s-spring to the posi and it has made a diff in feel..for the better! now hopefully the traction part will follow...

NEstyle · 07-05-2020, 04:38 PM

Can anyone tell me what's going on with this pattern? It looks nothing like any I have seen for two cut gears. The factory pinion shim was 0.025". Drive side was too close to the heel and the coast side was too close to the toe, so I added 0.005" to the shim. It didn't actually change the pattern at all. These photos are with the 0.030" shim. Both the drive and coast sides look too close to the face, right?

I actually don't know if my rear was ever opened up before, so I'm not sure what the factory pinion shim is. What have people seen for shims in theirs?

samman11 · 07-07-2020, 07:18 PM

I'm having my local Chevy dealership install 3.91 in my 2011 SS convertible. About $1550 for all costs. No way I would attempt this in my driveway unless I had a lift, proper tools AND an expert to guide me. I can't wait to see what this car is like afterwards.

NEstyle · 07-07-2020, 10:37 PM

You guys probably aren't going to believe this, because I probably would not have believed it if it didn't happen to me, but the weird patterns I posted in post #87 were due to low quality gear marking compound. I used Ratech 500 gear marking compound in those pics which basically wiped completely off of every tooth, making the pattern unreadable.

I kind of suspected that the compound was the issue, so I got some Richmond compound and I can now read the pattern beautifully. It's pretty wild that such a crappy compound even exists and I just wanted to make you guys aware.

I found someone else who noticed the exact same thing. This guy's review on Amazon sums it up pretty nicely.
https://www.amazon.com/gp/customer-r...SIN=B001P2D27U

He mentioned in another review on Summit that he tried the Richmond compound which he liked better than the Permatex Prussian Blue.

So, in summary, do not buy Ratech gear marking compound. Hopefully this saves at least one other person some headaches.

samman11 · 07-08-2020, 07:40 PM

Here's a few pics of the work so far. NOT something I would want to undertake in my driveway. Look at all that was removed.

samman11 · 07-08-2020, 07:42 PM

Sorry for the tilted pictures. Not sure why that happened. How to I rotate them?

NEstyle · 07-16-2020, 12:34 AM

Well add me to the list of cases where the factory pinion shim (0.025") from my 3.45 rear was perfect for my GM 3.91 gears. I had to change the carrier shims quite a bit, but I installed a Truetrac at the same time. My Truetrac, from bearing race to bearing race, was a lot wider than the factory carrier from bearing race to bearing race. I kept the same preload on the new carrier. After all was said and done, I ended up with 0.002" - 0.0035" backlash with a perfect pattern.

Overall, they set up well, but I was not impressed with the quality of the gears. The first set of gears had a huge ding on the face of one tooth that created a high spot on the drive side of the tooth (this gear set was returned) and both sets had huge burrs on the pinion gear, where the shim seats, that had to be ground down. The 3.45 set that I removed did not have this issue because the bearing/shim seating surface sat proud of the end of the pinion teeth. There were also tons of burrs on the ring gear mating surfaces of both gear sets, but this was not difficult to fix.

NEstyle · 07-16-2020, 12:42 AM

Quote:

Originally Posted by samman11

Here's a few pics of the work so far. NOT something I would want to undertake in my driveway. Look at all that was removed.

I'm sure all is well, but your dealer didn't have to remove a lot of the stuff that he removed. There is no need to remove either axle and absolutely no need to remove anything at all from the passenger side to get the rear out. The driveshaft does not need to be disconnected from the trans, either. The center support and diff flange are all that needs to be unbolted. Just pointing this out so people don't remove more than what's necessary when they attempt this.

acammer · 07-16-2020, 08:11 AM

Quote:

Originally Posted by NEstyle

I'm sure all is well, but your dealer didn't have to remove a lot of the stuff that he removed. There is no need to remove either axle and absolutely no need to remove anything at all from the passenger side to get the rear out. The driveshaft does not need to be disconnected from the trans, either. The center support and diff flange are all that needs to be unbolted. Just pointing this out so people don't remove more than what's necessary when they attempt this.

I've heard of people getting them out without pulling either axle, but that's never worked for me. It doesn't take long to pop it out of one side, then it's cake when you pull the diff down. Agree on the DS, I unbolt at the diff and ratchet strap up out of the way.

NEstyle · 07-21-2020, 11:22 AM

Does anyone know the part number for the pinion nut?

sinlinson · 08-12-2020, 10:21 AM

Did my 3.91 swap a few weeks ago. It's like a different car!! Got my center cection off ebay for $550. Paid a local Camaro Guru $350 to swap center cections, install BMR lowering springs and a Borla Atak exhaust. Car crirps second gear without really trying. No more bucking in first gear. And 6th gear is reachable without doing 85 mph. Seems like the gears these cars should come with.

NEstyle · 08-12-2020, 10:56 AM

Quote:

Originally Posted by NEstyle

Does anyone know the part number for the pinion nut?

AAM 40037574 is the nut. They're identical to the factory nuts.

Hulk · 08-13-2020, 06:38 AM

Wanting a 3.91 diff for mine but either cant find one or don't have the money when I do. Someday the stars will align.

04-01-2016, 07:49 PM	#85
blakjak55 drinks virgil's Drives: 2010 2SS M6 Join Date: Feb 2014 Location: Missouri Posts: 448	I replaced all mine when I did mine at 50k miles and some change. The carriers would have been fine except the races had some pitting and the inner pinion bearing sometimes will get the cage stretched during removal. Up to you but the carriers and races should be just fine. Pinions I would replace both with new races. __________________ 2010 2SS/RS M6 - CAI Intake - Borla Stinger - VTC - 3.91's Eibach Sways - LG ZR28's - BMR Springs - 285/35 Squared

09-26-2017, 08:59 AM	#86
frankwjr Drives: 2010 SS 2SS M6 Join Date: Aug 2016 Location: Smithsburg, Md. Posts: 2,446	Just finished up my 3.91 upgrade...replaced all bearings/races due to mileage(actually everything inside looked perfect!) so this was a bit more involved that just a gear swap...just want to add that even after all of the extra stuff I did, the ring and pinion went back in with factory shims and a .002 backlash and perfect pattern...freakin wild! Also added a Ford s-spring to the posi and it has made a diff in feel..for the better! now hopefully the traction part will follow... __________________ 2010 SS 2SS M6 - Tune by RDP dynoSteve!(Woot) - Daily Driver - *150K!* - All work by me...

07-08-2020, 07:40 PM	#90
samman11 Drives: 2011 Camaro SS Convertible Join Date: Nov 2015 Location: Rochester, NY Posts: 671	Some pictures of 3.91 install Here's a few pics of the work so far. NOT something I would want to undertake in my driveway. Look at all that was removed. Attached Images

08-13-2020, 06:38 AM	#98
Hulk Drives: 2011 Synenergy Green 2SS/RS Join Date: Jan 2011 Location: Pueblo, Co Posts: 556	Wanting a 3.91 diff for mine but either cant find one or don't have the money when I do. Someday the stars will align. __________________ 2011 Synenergy Green 2SS/RS Automatic.

07-05-2020, 04:38 PM	#87
NEstyle Drives: Caprice Join Date: Nov 2016 Location: SE PA Posts: 194	Can anyone tell me what's going on with this pattern? It looks nothing like any I have seen for two cut gears. The factory pinion shim was 0.025". Drive side was too close to the heel and the coast side was too close to the toe, so I added 0.005" to the shim. It didn't actually change the pattern at all. These photos are with the 0.030" shim. Both the drive and coast sides look too close to the face, right? I actually don't know if my rear was ever opened up before, so I'm not sure what the factory pinion shim is. What have people seen for shims in theirs?

07-07-2020, 07:18 PM	#88
samman11 Drives: 2011 Camaro SS Convertible Join Date: Nov 2015 Location: Rochester, NY Posts: 671	I'm having my local Chevy dealership install 3.91 in my 2011 SS convertible. About $1550 for all costs. No way I would attempt this in my driveway unless I had a lift, proper tools AND an expert to guide me. I can't wait to see what this car is like afterwards.

07-07-2020, 10:37 PM	#89
NEstyle Drives: Caprice Join Date: Nov 2016 Location: SE PA Posts: 194	You guys probably aren't going to believe this, because I probably would not have believed it if it didn't happen to me, but the weird patterns I posted in post #87 were due to low quality gear marking compound. I used Ratech 500 gear marking compound in those pics which basically wiped completely off of every tooth, making the pattern unreadable. I kind of suspected that the compound was the issue, so I got some Richmond compound and I can now read the pattern beautifully. It's pretty wild that such a crappy compound even exists and I just wanted to make you guys aware. I found someone else who noticed the exact same thing. This guy's review on Amazon sums it up pretty nicely. https://www.amazon.com/gp/customer-r...SIN=B001P2D27U He mentioned in another review on Summit that he tried the Richmond compound which he liked better than the Permatex Prussian Blue. So, in summary, do not buy Ratech gear marking compound. Hopefully this saves at least one other person some headaches.

07-08-2020, 07:42 PM	#91
samman11 Drives: 2011 Camaro SS Convertible Join Date: Nov 2015 Location: Rochester, NY Posts: 671	Sorry for the tilted pictures. Not sure why that happened. How to I rotate them?

07-16-2020, 12:34 AM	#92
NEstyle Drives: Caprice Join Date: Nov 2016 Location: SE PA Posts: 194	Well add me to the list of cases where the factory pinion shim (0.025") from my 3.45 rear was perfect for my GM 3.91 gears. I had to change the carrier shims quite a bit, but I installed a Truetrac at the same time. My Truetrac, from bearing race to bearing race, was a lot wider than the factory carrier from bearing race to bearing race. I kept the same preload on the new carrier. After all was said and done, I ended up with 0.002" - 0.0035" backlash with a perfect pattern. Overall, they set up well, but I was not impressed with the quality of the gears. The first set of gears had a huge ding on the face of one tooth that created a high spot on the drive side of the tooth (this gear set was returned) and both sets had huge burrs on the pinion gear, where the shim seats, that had to be ground down. The 3.45 set that I removed did not have this issue because the bearing/shim seating surface sat proud of the end of the pinion teeth. There were also tons of burrs on the ring gear mating surfaces of both gear sets, but this was not difficult to fix.

07-21-2020, 11:22 AM	#95
NEstyle Drives: Caprice Join Date: Nov 2016 Location: SE PA Posts: 194	Does anyone know the part number for the pinion nut?

08-12-2020, 10:21 AM	#96
sinlinson 2016 2SS Convertible Drives: 2011 Camaro 2SS convertible Join Date: May 2019 Location: NY Posts: 85 View My Garage	Did my 3.91 swap a few weeks ago. It's like a different car!! Got my center cection off ebay for $550. Paid a local Camaro Guru $350 to swap center cections, install BMR lowering springs and a Borla Atak exhaust. Car crirps second gear without really trying. No more bucking in first gear. And 6th gear is reachable without doing 85 mph. Seems like the gears these cars should come with.