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What good ratio for 37" on GM 10 Bolth 8.5

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kuht

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Brother!I have K5..1984..6.2 diesel..automatic transmission 4 speed with overdrive...i want instalation 37" tires..what ratio need for differential GM 10 Bolth 8.5 in for comfort drive and good and speed work automatic transmission box and part-time drive in mud? i dont use car only in mud..Thanks!
 
My openion, 4.56 is what I would run with 37's and and OD trans thats also a daily drive truck. For better off road ability if you want that, 4.88's. I'm installing 4.88's with 38 tall tires with an overdrive trans and deep transfer case gears. Will probably run 42' tall tires at some point.
 
so..if i instalation 4.88 in diff rear and front this be good for 37''and comfort drive and good for part-time off-road ? what ratio have GM 10 bolth 8.5 have from factory?hm..i dont know...thanks for answer!
 
i found a pretty cool chart online and it said with 35s 3.73 would be a good choice for fuel milage 4.11 for a "back to stock" situation and 4.56 for more power,it should be pretty close for your situation
 
rdn2blazer said:
My opinion, 4.56 is what I would run with 37's and and OD trans thats also a daily drive truck. For better off road ability if you want that, 4.88's. I'm installing 4.88's with 38 tall tires with an overdrive trans and deep transfer case gears. Will probably run 42' tall tires at some point.
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I concur.
 
10bolts will not hold up to serious off roading with 37s.

Unless you upgrade your shafts and components.

14b D60 would be my recommendation, if you run any size over 35s.

But this is only my opinion.
 
Doc Feel Good said:
10bolts will not hold up to serious off roading with 37s.

Unless you upgrade your shafts and components.

14b D60 would be my recommendation, if you run any size over 35s.

But this is only my opinion.
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rubbish, my 1/2 ton axles lasted years on the trails with 35s then 37s. then more 37s. 4.56 gears were nice on the road but 4.88s and jsut keep the top speed down some.
 
If the OP was in the U.S. I would say don't waste your time with at least the rear 10-bolt, however I doubt 14FF's are very common in Russia.

In regards to gear ratios, I have owned a 6.2/auto w/ OD for a long time and have ran the following combinations:
32" tires, 3.73 gears
33" tires, 3.73 gears
33" tires, 4.10 gears
35", 38", and 39.5" tires with 4.10 gears (off-road only now so I don't care about the road)

The 32/3.73 or 33/4.10 combo were excellent on the road including sustained 70 mph trips on the freeway. The transmission would actually hold OD on moderate grades. Back calculating the RPM with those combinations I would recommend at least 4.88 gears with 37" tires. This would get you right in the same rpm range. Keep in mind that there is more to it than just the larger diameter tires, as a 37" tire compared to a 33" taller is heavier with more rolling resistance.

I think OD in the transmission would be pretty much worthless with the 4.56/37" tire combo
 
Ratio

i think the best Ratio would be Dana 60/Corp 14 for 37" tires, i have had 38's on 10 bolts and its no fun when your the only one in the group that has to be trailered because your shafts let go.

im poor so i have a 8 lug Dana 44 up front with upgraded shafts and a Corp 14 out back.

i call it PIECE of MIND now

but if you are looking for a different ratio for them corperate 10 baby pumpkins i would be all over a set of 4.56's and or 4.88's

these are just my opinions. i am not here to say you HAVE to have 1 Ton stuff. just trying to make sure your aware the size tire your wanting to run and the failure rate of the axles in my own experiance. but hey if you want to look cool going to the mall i totally undertand
 
Your solution may be the problem you end up with. 4.88 is your best bet to keep it feeling good on the road and keeping up with traffic without your trans hunting from 4th to 3rd constantly. The problem is that with 4.88 the pinion is wussy and tiny in diameter
 
he's got the diesel, he doesn't want to be spinning rpms that high w/ 4.88s on the road. your diesel came w/ axle gear sets 2 taller (lower number) than the equivalent gas engine/ axle combo (3.08s vs. 3.73 for the gassers). keep that in mind. most guys will tell you 4.56s are perfect for 35s and 4.88s for 37s on a gas powered truck. i'd stay in the 4.10 range, absolutely not lower than 4.56 or you'll never get up to highway speed.
 
runamok151 said:
he's got the diesel, he doesn't want to be spinning rpms that high w/ 4.88s on the road. your diesel came w/ axle gear sets 2 taller (lower number) than the equivalent gas engine/ axle combo (3.08s vs. 3.73 for the gassers). keep that in mind. most guys will tell you 4.56s are perfect for 35s and 4.88s for 37s on a gas powered truck. i'd stay in the 4.10 range, absolutely not lower than 4.56 or you'll never get up to highway speed.
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I'm going to guess you have never driven a 6.2 powered truck. This is NOT something like a Cummins with 400 lb-fts of torque at 1,500 rpm. Put 4.10's in it with 37's and I guarantee you that overdrive/4th gear will be useless. 4.88 gears x 0.70 OD ratio = equivalent of only running 3.42 gears in a non-OD truck with 37" tires. Now go find me somebody on this board who will say that 37's and 3.42's will make your rpm too high......

By the way, my 6.2 Blazer rolled out of the factory with 3.73 gears and 235/75R15 tires.
 
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