need some rear axle ratio help

[stepsideD]

can't find a stamp on the axle, at work now and can't jack up the rig and turn the rear wheel (plus that may be too inexact for me) and want to know my ratio! my rpo code is GQ1, which is "Rear Axle - Standard"

does anyone know what ratio was standard on a 1982 c10 stepside with 6.2 diesel and 700r4 transmission? or where I could locate this info on the web?

[DmaxMaverick]

"Standard" only means is isn't a custom, or fleet special option. There should be another RPO, which will indicate the actual OEM ratio for your truck. The "standard" ratios for your truck could have been either 3.42 or 3.73. If you also have a Z71, or Z82 RPO, yours will more likely be 3.73. However, it is not conclusive. Much depends on what the original dealer ordered from their allocation, but they usually order them according to the "standard", which can be effected by other RPO's. If it was a customer ordered truck, it could be either, regardless of other options. A 4.10 is possible, but I don't think it would be accompanied by the GQ1. I could be wrong, but I don't think 4.10 was available on a shortbed (including stepside), and was only an available option for the "heavy half" long bed.

All that aside, what is your tire size, and at what speed does your TC lockup, under normal, light/moderate acceleration driving? It should be pretty consistent.

[atmdoc]

For what it's worth, I had a 86 Blazer with the 6.2 and 700R4 and it had 3.08 gears.

[stepsideD]

All that aside, what is your tire size, and at what speed does your TC lockup, under normal, light/moderate acceleration driving? It should be pretty consistent.

235/75R15, and the speedo still doesn't work so I can't answer the rest. and how do i tell when the torque converter is locking up?


There should be another RPO, which will indicate the actual OEM ratio for your truck.

i've got the decal from the dash right here and that is the only code that references the rear end, besides a g50 for heavy duty rear springs.


For what it's worth, I had a 86 Blazer with the 6.2 and 700R4 and it had 3.08 gears.

how much variation in stock axle ratios is there for each model? do you run into other blazer owners with the 6.2 and 700r4 with different ratios from the factory?

[Robyn]

The only for sure way is to yank the back cover off the diff and roll the gears around and look a the nomenclature on the ring gear. The ratio will be stamped on the gear. It will have number of teeth on ring and pinion and not the actual ratio. You can simply do the math and your there.
The common one was 3.42 but as has been mentioned 3.08 was there too. The 3.73 or 4.10 would have been and order item most likely

[stepsideD]

The only for sure way is to yank the back cover off the diff and roll the gears around and look a the nomenclature on the ring gear. The ratio will be stamped on the gear. It will have number of teeth on ring and pinion and not the actual ratio. You can simply do the math and your there.
The common one was 3.42 but as has been mentioned 3.08 was there too. The 3.73 or 4.10 would have been and order item most likely

can we figure it out by stock tire size? i know that 225/75r15 was original, and with engine rpm at 1800, .696 overdrive, and 3.08 ratio, that's about 70 or 71 mph.

with a 3.42 thats about 63 or 64 mph at 1800 rpm

which sounds more likely for a stock setup?

[a5150nut]

Couldn't you get in the ball park by jacking the rig up and have someone mark and turn the tire thru several full rotations and lay underneath with a mark on the drive line and count the revolutions there? Wouldn't be exact but might get what he needs.:rolleyes:

[NutNbutGMC]

Couldn't you get in the ball park by jacking the rig up and have someone mark and turn the tire thru several full rotations and lay underneath with a mark on the drive line and count the revolutions there? Wouldn't be exact but might get what he needs.:rolleyes:That will work. That's what the ratio is based on from the get-go.

That is most likely a 3.42:1.