Question for those with 4.10's

[flstang65]

For those of you that have 4.10's, what rpm's are you turning when you are running 70 mph and then 75 mph? I was driving to work the other day and there was a sign showing everyone's speed. Either they upped the speeds to scare people to slow down, or my car is still off. I got the complete built rear end (with less than 5000 miles on it) out of my friends Saleen that he totaled, and he was insistent that they were 4.10's. I have corrected the computer with my tuner. I'll post the rpms for my speeds later after I can get it on the highway again, I am having one huge brain fart right now. The rear end is an 8.8, 31 spline axles, Auburn posi. and I run either my stock 245/45 17's or 275/45 17 drag radials.

BTW, I only paid 200 for the whole thing! Then I sold off my stock rear for 350.

 

[joshjwc9]

Sounds like you have either 3.55 or 3.73, but if I were you I would jack up the car and check the driveshaft revolutions...

 

[flstang65]

i checked it before i installed it while i had the whole rear end out of the car. my friend and i checked it countless times and both came up with around 4 revolutions of the yoke per one revolution of the axle. maybe im just losing my mind???

 

[flstang65]

Well, after doing some HW and using the ever so valuable search feature here on stangnet, I have come to the conclusion that I do, in fact have 4.10's I called the guy I bought the rear from to confirm and hes going to fax me a copy of the receipt just for my piece of mind. Lol. Thanks for looking anyways guys.

 

[trinity_gt]

i checked it before i installed it while i had the whole rear end out of the car. my friend and i checked it countless times and both came up with around 4 revolutions of the yoke per one revolution of the axle. maybe im just losing my mind???

The difference between 3.7 turns and 4.1 turns may not be easy to distinguish. If you can, try turning the wheel ten times and look for ~35, ~37 or 41 turns of the driveshaft.

Or you could remove the rear cover and count gear teeth to know exactly what you've got.

 

[SVT32VDOHC]

I have a 96 Cobra with 4.10's T45, 23 tooth white speedo gear with 275-40R17's and my speedo is right on. I just put a new gear on the tail shaft of the transmission too, so I know it's perfect. At 80MPH I am at 2,900, so 70-75, it's prolly 2,600-2,700.

I know it used to be off because after I smoked two speedo gears, it dished the drive gear on the tail shaft and at 90MPH it was reading 3K, so I knew it was 10 fast. I just had all that fixed in November.

 

[Tim2002GT]

With 275/40/17's, at 70 mph I am turning a hair under 2400 rpm. I have 4.10's also.

 

[COramprat]

At 70 I am at 2600...245/45/17's up front.

 

[ErikTheBeast]

With my 285/35/18's and my 4.10's I'm @ 2500 doing 70 ( I have a 4r70w btw )

 

[BurningRubber]

This is with a T-45 transmission, RPM's will be slightly less with a T-3650 as 5th gear is a little deeper...

315/35/17 tires out back, speedo corrected with a Diablosport Predator.

YouTube - 4.10's 60-80mph, RPM check.

 

[Tim2002GT]

Guess I should add that I also have a 3650.