what gears i need?

[camaney]

o.k here is the deal i have 70 chevy truck with a 6 cyl. 292. auto trans. th350 and i think the gears are 3.73 i drive it a lot on freeways and at 3000rpm i get 65mph and i want to go a little faster at 3k.rpm what gears do i need and how hard is to change the gears on the differential has anybody done it with regular tools also what do i need besides the ring and pinion? thanks in advance

[WIDESIDE72]

My dad has a 71 GMC with a 250 6 cylinder. He had 3.73 gears and the same problem as you. We bought a complete 3.07 rear for $150 and swapped it in. This lowered the RPMs dramatically. The 3.07 gear is OK if you don't plan to tow anything more than a boat or small trailer, less than 2k lbs. Otherwise, gears in the 3.42 range will give you a little more speed at the same rpm. You will need to buy gears and if you do not have experience, have someone set it up. Gears start at around $150, another $150 or so to set it up. You will also need a shim kit (around $50) and depending on the condition, plan on another $100 or so for bearings and seals. You will also want to look at your brakes when you have it apart. Have you considered swapping in an overdrive trans? If you have a powerglide or TH350 in there now, a 2004r can be swapped in without cutting the driveshaft. It is a little more expensive, but you will get he lower cruise RPMs without giving up your low end grunt of the 292. As a matter of fact, it will be even better, as the 200r has a lower 1st gear than a PG or TH350. You will probably bark the tires going into 2nd!

[Longhorn Man]

to keep it real easy, and to make it cheap, I would recomend swapping out the whole rear axle for a 3.07 geared axle. most 1/2 ton/automatic trucks will have it.
This assumes you have a C/10, and not a C/20. If you have a C/20, it will be rather expensive to 'fix'this issue.

[jim zag]

I have the 3.07 rear end and 255 70 15 tires and my truck cruises just FINE. Just go find a complete rear and swap it in and try it!!!!

[Shaky]

I set-up 3.07 gears in my 12-bolt for my '66. The only special tools you need are some way to accurately measure pinion depth. Between that and all the shimming required, it would be a lot easier if you could get an entire rear assembly...

[67chevy3/4tontruck]

they are all good gears

[LONGHAIR]

Originally Posted by 67chevy3/4tontruck

they are all good gears

........what?


Yeah, as the others have mentioned, it is far easier and cheaper to swap out the entire rear-end. The "average guy" really should not be messing with a ring and pinion swap. It is a very complicated thing that does not translate well to reading. It needs to be seen, while being taught by someone with experience.

[short step]

ut 307s in my 71 w 307 & 200r4 its great 65@2000rpm. if u get a later 12 bolt it will be 6 lug , just use your axles brakes and drums.i changed my diff because i had air ride welded to my housing.
bob

[short step]

if u dont need posi get a 10 bolt , junk yards are full of blazers and suburbans , pull the cover and check the ratio.
bob

[WIDESIDE72]

Originally Posted by short step

if u dont need posi get a 10 bolt , junk yards are full of blazers and suburbans , pull the cover and check the ratio.
bob

Huh... the yards around here are full of front wheel drive throw away cars... You see a few mid 80's trucks, and a lot of 90's trucks... I am not too sure it would be a direct swap...For instance if you tried to put a later model axle that was meant for leaf springs under a truck that has coils... In other words, a little research would be in order. No use trying to re-invent the wheel...

[WIDESIDE72]

Originally Posted by short step

if u dont need posi get a 10 bolt , junk yards are full of blazers and suburbans , pull the cover and check the ratio.
bob

BTW, being a 10 bolt has nothing to do with whether or not it has a posi...

[Longhorn Man]

and it is safe to assume it is a coil spring truck since it is a 70 chevy... putting a 10 bolt in there would be lots of welding and jazz that isn't needed with a proper 12 bolt rear.

[camaney]

thanks a lot folks i guess i'm going to the junk yards next weekend hunting for that rear end. thank you again