View Full Version : How to tell gear ratios off the vehicle?
TrailBlazzin
10-28-2008, 08:53 PM
Is there anyway to tell what the gear ratios are on a differential for the front and rear without actually knowing the vin of the vehicle it came from?
Are there part numbers or any other values that would give it away??
Super 88
10-28-2008, 10:15 PM
Is there anyway to tell what the gear ratios are on a differential for the front and rear without actually knowing the vin of the vehicle it came from?
Are there part numbers or any other values that would give it away??
Look in your glove box. There will be several 3 digit codes. You are looking for one of 3:
GU6 = 3.42 Ratio
GT4 = 3.73 Ratio
GT5 = 4.10 Ratio
TrailBlazzin
10-29-2008, 07:21 PM
ok, what i meant was is there anyway of knowing without seeing the vehicle at all. i know the rpo codes and where to find them. I have loose differentials completly removed from the original vehicle and don't know the vin from which they came.
WOOLUF1952
10-29-2008, 07:43 PM
The only way I know of for sure, is to open the pumpkin and count the teeth. Turning the input shaft and counting the turns of the axle gets you close.:m2:
06Blazer88
10-29-2008, 08:10 PM
:iagree:
TrailBlazzin
10-31-2008, 03:05 PM
what about the front differential?
i bought a used front and need to double check and make sure it is in fact the 3.73
mattj21
11-04-2008, 01:00 PM
which one is the best one to have for offroading
gmac310
11-04-2008, 01:19 PM
I'd have to say the taller the better, in other words go for 4.10s. It would give you more low end grunt but worse gas mileage.
Robert1101
11-04-2008, 01:45 PM
Open it and count the teeth on the Pinion and the Ring. Divide the pinion into the ring and you got it.
mattj21
11-04-2008, 02:15 PM
ahh i got the 3.42 without the g80 bummer
gmac310
11-04-2008, 04:54 PM
ahh i got the 3.42 without the g80 bummer
I have a g80 with the 4.10s but I don't notice any advantage to having the posi but then I don't do any offroading and I haven't driven it in the snow yet either.
pjaneiro
11-12-2008, 02:15 PM
I use teh good old fashioned way...
lift the truck (rear) and spin the wheels, and both of them spin the same way, you have a g80, mark the tire and the shaft, count how many times the shaft turns as yuo do a full rotation of the tire...
just like a clock check where it stop, a bit past 4 ? 4.10 it shows 3 and turns (about) that's 3.73 and a bit shy of a 3: and half turn s that's a 3.42 gear set
the same goes for open diff.s , only difference is leave one of the rear wheels on the ground...