sprech

iTrader: (1)

I'm trying to figure out what rear end gear ratio to put in the wagon. L96 with 6L90E and the trans gearing is as follows:
1 2 3 4 5 6 R
4.027 2.364 1.532 1.152 0.852 0.667 3.064

The car came with 3.08's and I was thinking of going back with them, but that might be too short of a gear as it will put 50 mph rpm at about 1,300.

Right now I'm going with 255/50/17's that are 27.04" diameter.

It seems that the best pricing is on 3.73's.

50 mph: 1550 rpm
65 mph: 2000 rpm
75 mph: 2300 rpm
100 mph: 3000 rpm

What's the difference between the regular Richmond gears and the EXCel gears aside from the price?

Project GatTagO

iTrader: (7)

I would keep the 3.08 gears. this will lover your driveshaft speed and make it less prone to drive lien vibrations, which is a real issue with these swaps, especially if the car is lowered. If the engine is stock, you won't have any issues going down the highway with those gears. Your statement about 1300 rpm at 50mph is a non issue. What's the RPM at 75mph? That's highway speed.

Andrew

Fry_

This should help.
http://xse.com/leres/bin/gearratio?t...rofile=&wheel=
It's pre set for a t56 but you can change all of the variables.

alocker

iTrader: (10)

The 3.08/6L80e will be like having 4.88's with a TH400 in first gear. That 6.0 will have no problem lugging at 1550 unless you are putting a huge cam in it. Plus like Andrew said, driveline vibes are a real issue that can be a pain to fix.

sprech

iTrader: (1)

Thanks for the input guys and thanks for the calculator. From what I understand, unless in sport mode, first gear is only used the first time there is forward motion. After that it will shift through gears 2 - 6.

As far as the size, I get the argument to go 3.08 and there are compelling arguments to go at least 3.23-3.55. I just wish I had more data to help me make the decision. I guess worst case, I go one direction and if it doesn't work out I have another ring and pinion installed.

1989GTA

I have a 6L80 in my 65 Skylark and has the same gear ratios. I opted for the 3:23 ratio because it gave a good combination of cruise rpm and acceleration when needed. My rear tire is 285/40ZR17 with a 26" diameter. So for you with a taller tire maybe in the 3:40 to 3:50 range. I wanted to be around 1900-2000rpm at 70mph for my car.

Jimbo1367

As far as the brand of rear gear, I would check into the GEAR & AXLE section here. Richmonds tend to be noisy from what I read there. I always thought they were the "go to" gear. From what I've read, Motive GEar seams to be the gear of choice. I forget what color box is their street gear. Orange or blue.

sprech

iTrader: (1)

I'm going to drop the unmolsted axle back in there after I do the F-body brake upgrade and drive that for a little while to see what I think of the 3.08's and go from there. Thanks for all of the help guys!

casias

iTrader: (1)

I have a 6L90 from a GMC sierra in my dakota pickup (4200 lb). I have 3.92 rear gears, with 27 inch tall tires. It runs about 2300 RPM at 60 mph (I don't know that exact numbers, because I can't remember). If I would choose gears in this truck, I would probably go with 3.55 or so. But the rearend is solid, so I don't have any reason to change right now.

With this combination, it pulls super hard.

Not sure if any of this information helps.

Project GatTagO

iTrader: (7)

That's what I would do! Those gears are already there, so why mess with it? If you don't like it, you can always swap them later!

Andrew