Tilted Front Differential w/ Fabtech Lift

Jon9116 · September 18, 2012

Well, just got an email from my differential shop saying the 4.88s were installed and the truck was ready for pick up. I wish I could be happier but some other news was reported. This is there second attempt with the front gear install. What happened is apparently with the fabtech 6in lift, the front differential is tilted ALOT. So with the first attempt at installing the gears, on the test run the bearings burned up because they weren't getting oil.

The cool guy that Jason over at Texas Drivetrain Performance is ordered new gears, bearings, seals on his dime to replace this. On the second install he said he had to "overfill" the differential to ensure the bearings would be lubricated and able to get oil but recommended I take the truck to a lift shop because the tilt was so sharp.

So I go to work and try to find similar scenarios. I've come up short so far with GM/CHEVY situations. However, I found similar stories with other vehicles with the Fabtech lift doing this and Fabtechs recommendation was to "overfill' the differential as well..

Does this seem right and is this a permanent, safe fix? Fail on Fabtech's part?

latreille89 · September 18, 2012

I would assume as long as they get cooled, there shouldn't be any issues. Not sure what the long term effects are of overfilling a diff.

mdauwald · September 18, 2012

Jason's a good guy. Glad to see he's still around. I'm not sure you have any real long term concerns either except making sure it stays overfilled

blackout07 · September 18, 2012

The only thing I can think of is if the diff drops were installed incorrectly. Maybe backwards or even upside down. It's a full diff drop so there is another issue. Pics please and which way is it tilted?

ruggedlife · September 18, 2012

it will always be tilted no matter what to keep drive line angle at a minimum. when i did a cognito 10-12" i had to add quite a bit of fluid to the front and rear diffs. this sounds normal and correct to me

latreille89 · September 18, 2012

I guess what the main question is, do they tell you that you require to put more fluid in the diff in the instructions from the lift? Sounds like to me of they tell you an amount, then do it and if it causes it to fail, go after the manufacture of the lift. If they don't, and you diff blows from the angles and not getting enough fluid, go after them for not mentioning that this may happen. It should all be part of the install instructions since you clearly need to change its angle.

blackout07 · September 19, 2012

it will always be tilted no matter what to keep drive line angle at a minimum. when i did a cognito 10-12" i had to add quite a bit of fluid to the front and rear diffs. this sounds normal and correct to me

I could see it with a 10 -12" lift but not the Fabtech. My diff doesn't appear to be angled at all. I wouldn't of thought that.

Doug_Scott · September 19, 2012

Does this diff not fill from a plug in the side? If so, it is real tough to over fill. Once it hits the open plug, it will just dump it on the floor. You will also want to watch for leaks at the axle seals on the diff. Not sure about a front diff that has no axle tubes, but on diffs with axle tubes, the axle seals are not really designed to run in a tube that is completely full of diff oil. Also look at the vent for the housing, make sure it is as high up as it can be.

If the front pinion is pointing upwards, you will also want to ensure the oil is high enough to cover pinion bearings. Diffs gets some of their oil distributed by the rotating ring gear and the rest by having oil level high enough to get down the axles, and over the carrier bearings.

Generally pinion angle should be kept at 3 degrees or lower. Any higher and you will get a vibration, lots higher, ujoint will likely fail, or at the least, shake the living shit out of the truck.

ruggedlife · September 19, 2012

i believe most all somewhere in the end tells you to check the fluid levels

ruggedlife · September 19, 2012

http://www.fabtechmotorsports.com/pdfs/instructions/Fabtech-install_FT21046i.pdf

there's the instructions, page 19 step 53

brainpause · September 20, 2012

If someone really needed to put more fluid in the diff than the side hole allows, could you put fluid in through the vent hose, or is there a one way valve?

blackout07 · September 20, 2012

my diff is fine...its a full drop so it should sit as stock

Is yours angled at all?

ruggedlife · September 20, 2012

i have never once installed a lift kit on a gm that keeps the front diff as level as stock... and trust me i have installed my fair share of lifts. every kit i've ever done has angled brackets to some extend to drop the diff. if you look here at the picture of the fabtech lift kit, the two brackets right below the steering knuckles are what drops the diff. and they are clearly angled

http://www.fabtechmotorsports.com/products/cart.php?m=product_detail&p=111&display=GMC/CHEVY%204WD

and again in their instructions

http://www.fabtechmotorsports.com/pdfs/instructions/Fabtech-install_FT21046i.pdf

page 9: step 18 tells you to put the wider end towards the front. also shows the picture of the bracket very clearly that's angled... this is done to help with the front drive shaft angle. just like you would install pinion shims in the rear so the driveshaft lines up better after you lift certain ways

blackout07 · September 21, 2012

I always thought they were angled on top to match the contour of the frame.

Jon9116 · September 22, 2012

Thanks for all te comments guys. I wish I could provide pictures but I'm still overseas and I myself haven't even seen this angle he's talking about and it's driving me nuts. I wish I could at least see how "sharp" this tilt is. Fabtech confirmed it is suppose to be slightly titled however Jason makes it seem like is not right and tilted greatly...

He said he completely filled the differential and recommends I don't go 4wd until I get a lift shop to check it out. He did say he doesnt know much about lifts because they don't do them.