I was curious, does anyone know how to tell if the entire diff (pumpkin) is a true GTUs diff? As in the ratio of 4.33. I was searching previous posts and saw someone had a technique of marking the drive shaft and then spinning the wheel once around, the driveshaft should rotate 4.33 times around or something.

Would I be able to do this if it's just the bare pumpkin? As in the gears are inside the diff but no 1/2 shafts to or driveshaft to measure how many times they turn.

Anyone?

 

if its a bare pumpkin then you can count the teeth and do the math: 33 ring gear teeth/ 15 pinion gear teeth =
2.2:1

mike

 

Yes, you can do that. Mark your halfshaft output flange on one side, and move it one full rotation. The driveshaft flange will move 3.9 times, 4.1 times or 4.3 times depending on the gear set. Mark the driveshaft flange to make sure you get a good starting point.

PaulC

 

Very cool! Thanks for the advice.

I don't think the gears are exposed so I'll do the trick you said Paul.

Do you think I'll be able to gauge the difference between 4.1 and 4.3 just by the number of rotations?

Maybe I'll practice on my stock 4.1's and see where it ends up so I can compare.

 

Yo,


Well, it sounds like it's not in the car...but if it is...

80mph on the speedo should be around 4,000rpm.

KS
1989 GTUs "Wave goodbye to your gas mileage..."

 

That's the tricky part, and why you have to mark very carefully, but yeah, I think you can.

PaulC

 

Like Paul said, carefully mark the driveshaft flange. Put you mark at the top and count the number of times it comes past the top as you turn the halfshaft flanges. A 3.9:1 won’t quite make 4 rotations, a 4.1:1 will make 4 rotations then go 36º further, and a 4.3:1 will make 4 rotational then go 108º (more that ¼ turn) further. Should be easy to tell.