OK guys, I'm just about ready (and so is the weather) to swap in my 3.27 and get rid of the 2.77.

The 3.27 has been taken apart, the iron calipers junked, everything cleaned, inpected, painted, and is just about ready for reinstallation. I can't find any info on what kind or how much fluid/lube I need.

Anyone know how much fluid I need?
Anyone have a specific type they recommend?

 

i used M1 75w-90 in my 9 bolt along with gm posi additive

 

It should take a hair under 2 quarts, IIRC.

I've read that if you use synth. fluid you don't need the additive, as it already has plenty of friction modifiers. That's just what I read, though.

 

there is a lot of confustion with the friction additive to use. the original formula is no longer sold through gm. the stuff at the dealer is the same stuff used on the 10 bolt rears.

 

OK, so what do I use. I'm now more confused than when I started!

 

well, if you use plain old gear lube then use the gm additive (that's what alot of us use) I don't know what is differant but, it seems to work


if you use synthetic don't use any



this is pretty much what people here are doing (in the many times this get brought up this is pretty much what people say they use)

 

I also have a 9-bolt rear end. Last time I drained and refilled it, I used a 50/50 mix of RP 75W-90 and Redline 75W-90. Both are full synthetics, and both have the LS friction modifier built in. You don't need to add any additional additive. Works great. No chatter on corners.

 

Just get some redline synthetic lube. You can get it at nearly any speed shop and you can order it online almost everywhere.

 

If you want the definitive answer to what to use in your 9 bolt read your owners manual. The only problem with that is GM no longer markets thier recommended special lube. I contacted the main offices in michigan back in 1989 to try and get an recommendation for an aftermarket equivalent. The only thing i got was the corporate slogan, KEEP YOUR GM PRODUCT ALL GM........ . They did however volunteer to send me a spec sheet for the product, but by the time i received it i already had located and purchased the GM product. Also according to the owners manual GM says not to use any type of friction modifyers in the 9 bolt. Judging by the look and feel of the GM product i purchased back in 89 i would say it is nothing more than a synthetic lube.

 

Owner's manual?



...I'll go synthetic. Thanks guys.

 

I did this exact same swap in the summer. I used some redline gear oil that already has friction modifiers in it so I added nothing. Works great too. Although the ratios are a huge change I noticed a nice difference in my car, especially when it goes into 2nd gear and the back kicks loose

 

Dober, you swapped in a 3.27 for your 2.77's, eh? ...and ya liked it? That's good to hear!!! I'm hoping for good things! With the cam, headers and 2200 stall, I lost a smidge of low end torque, so that gear should really help.

 

Haahah no man I went FROM 2.77s to 3.27s. Im using the 3.27 rearend and I only gained around 500 rpms at cruising speed.

 

Yeah, that's what I meant. I just worded it all bass ackwards!

 

Abubaca,

Did you finally go with your choice of just synthetic?

I was looking into new fluid for my diff. and spoke with a sales rep named Paul at thunderracing.com. He states that although there is a friction modifier in the synthetics, it isn't enough to accommodate GM's limited Slip Diff's.

How you want to take it, I don’t know. Maybe he’s just trying to get rid of the stuff he has in stock, but then again, maybe not.

Scott