Vader953

I have a 78 SA that has a stock TH 350 tranny. I have the stock 255 60 15 tires. At 80 mph, I run about 3800 to 3900 rpms. This seems really high, which leads me to believe there's no way my rear end is stock. Especially with the low gears offered with my tranny. Can anyone help?

My guess is I am running an aftermarked 3.70 or 4.11.

Thanks!

WA 2 FST

I estimated the loaded tire diameter at 26.75". All tires are a bit different, but the 255/60-15 is ~27" tall with no load (weight of the car) on it, so I should be close.

Assuming 3800rpm at 80mph, I come up with 3.78 ratio. Assuming 3900rpm at 80mph, it comes out to 3.88. So maybe either a 3.70 or a 3.90?


[Modified by WA 2 FST, 12:13 PM 1/15/2003]

bence13_33

Sounds like 3.70 gears.

69er

I do 3100-3200 RPM at 70 with 3:55's.

Could be 3:55's but you are probably right with 3:70's.

Vader953

Thanks guys.....that's what I wanted to know. Sure makes for a strain on the interstate, but man she will fly!

Wardog

Just to beat a dead dog, I have 3.364 gears and get 2500 at 60, 3000 at 70. You definitely have quicker gears than me!