2.79 Rears :/

Call truck pro. I just picked up 3.55 rears for my w900. Both for 4000.00 . Pain that they wanted old befor getting new. Fore the core. Then I put all new bears in wheels and out put shaft. In short spend few bucks now save tons later. But I have a barn to complete task.

 

What's the drive ratio of your transmission? If you're running a direct drive, switching to 3.55s is going to be closer to running 4.88s with an OD transmission than what you're expecting. Also, what size tires are you running? You need to factor all of that in to figure out where you're going to be at for cruising speed. To that end, swapping tire sizes might be a more economical way to get you to where you want to be vs. swapping out rears.
There's a formula for figuring it all out...
(##60)/(B*C*D)
A = engine RPMs
B = Rear end gear ratio
C = Transmission final drive ratio
D = Tire revolutions per mile

So if you're running a direct drive transmission now with those 2.79s and we'll say tires which give you 513 revolutions per mile, and you wanted to see where you were at 1500 RPMS...
(1500*60)/(2.79*1*513) = 62.88....

So you'd be running between 62 and 63 MPH at those RPMS. Change it up to 3.55s...

(1500*60)/(3.55*1*513) = 41.419.....

See the difference? Knowing your transmission drive ratio and tire revs per mile is important. The guy running 3.55s probably isn't using the same transmission as the guy running 2.64s or 2.79s.

 

Sounds like a direct. Find the model number and call a dealer.

 

On the right side of the dash, in front of the passenger seat, there's a panel you can remove and you should be able to see a spec sheet once you do... it will include the nomenclature of the transmission (e.g., RTLO16909A, FRO16210C, etc.), and you can determine it from that.

 

Get ahold of rebel127. Leave 2.79 w direct Trans get his ecm tuning with 171702 Borg Warner turbo. You will love it