Installing gears and true Trac,Not as easy as in other vehicles, Backlash questions.

[Joe.G]

So I installed GM 3.91 and True Trac, I used a Mock up pinion bearing and had a nice pattern and .005 Back lash, After I pressed on new bearing the pattern moved out on the teeth ( centered left to right still ) and back lash tightened up , I am hoping the rear will be quite and hold up but I could not re adjust with out getting a new bearing. With out a spreader the job is a pain as well. I am assuming everything will loosen up a little, I did take it for a ride and seems quite but didn't go far as I need alignment badly.


Getting the Preload in inch pounds is a pain as well, But everything feels good.

[oldman14ss]

sounds like you did well. i'm not good at installs but i did get ripped off. just an opinion,but i would drive it , monitor your temperature, and listen to see if you here whine the best way is to watch the temp. thats what i did on break-in so i didnt lose tempering of gears. you can get an infared temp gauge at harbor frieght for bout' 20 bucks has a little laser light and shine the dot on what you want to read and pull the trigger. real easy just got to get on your belly from the rear or car and point at the punkin.

[demonspeed]

If it’s quiet then I’d not worry about it. Hopefully you used gear oil recommend by Truetrac (non-synthetic) and did NOT add the limited slip additive.

[Joe.G]

What temp's am I looking for? I have a temp gun.

I used Toroco 80/90 Non syn no additive.

[oldman14ss]

i'm wanting to say below 200 degrees, not sure though. i know i saw the temperature on this web site just not sure. this getting old s??t sucks.

[oldman14ss]

i used lucas oil straight 80/90 gear oil no additives. like demon speed said if you dont hear dont worry cause you done good. if you did something wrong youll hear it. give me a little bit ill see if i can find the temp

[oldman14ss]

ls1gto forum guy says 135 to 140 degrees, no hotter cause it will cause the gear oil to get hot and break down. i remember now that was right and i wrote it down in my sevice manual. i was running about 120 degrees. when you break it in vary your speeds. what i did was take back roads vary my speeds and pull over after about 20 miles and let it completely cool down then start all over. its called tempering your gears. i had to think a minute. i remember now. unless you have money falling out your butt you can go run the crap out of it first thing. but i wouldnt go that rout. some people on hear will tell you to drive like you stole it. not me. hope this helps. the oldman..

[oldman14ss]

NOT 200 DEGREES !!!! my bad i apologize

[demonspeed]

I have the GM service manuals for 2013, but I don’t see anywhere it specifies proper operating temp. That said, some of the info and procedures are difficult to find as GM might refer to parts and whatnot in a different vernacular than some of us hillbilly hotrodders traditionally do, so I’ll reply back if I stumble across it.

[Joe.G]

How Many miles for break in? I am thinking I'll change the Fluid after about 500 Miles or should I do it sooner or wait a little longer? I am not going to drive it until after alignment and the weather this week isn't looking good here.

[WVracer]

Originally Posted by Joe.G

How Many miles for break in? I am thinking I'll change the Fluid after about 500 Miles or should I do it sooner or wait a little longer? I am not going to drive it until after alignment and the weather this week isn't looking good here.

Most break-in procedures say to keep the drives gentle and short for the first 500 miles. Drive it for 10-15 minutes, then stop and let the diff cool. Do that for a few times, then drive it gentle for the 500 while not exceeding 30 mintues or so without letting it cool. After that change the fluid and drive as normal

I don't know if all of that is necessary but that is what most recommend. I can't find anything about a break-in period in the service manual. However, it would be smart to inspect the gears after 500 miles to see how they are doing and if there is any excessive wear or shavings.

[demonspeed]

You may want to take a look through the Eaton installation manual if you haven’t already. That should explain proper break-in.

edit: I took a look and all it says is 50k mile service interval unless submerged in water/mud… which if anyone happens to find themselves in those circumstances with a 5th Gen then I have a feeling they’ll have much bigger problems than worrying about differential fluid

[Joe.G]

Lol, I figured 500 to 1,000 Miles I'll change fluid, I'll take it easy the first few trips and no hard launches for a while, I plan to go to Camaro Nationals this July not sure how many miles I'll have on it before then. Not sure how easy it is to pull cover with Diff in car to check gears.

[oldman14ss]

change after 500 miles. you didnt say if yyour set up is quiet? hope it is