What Gears

[nocok5]

My 1970 Blazer has the stock 3.07 gears and 33 inch tires. It is a dog off the line and I would like better low end performance so I can take it to the mountains and actually be able to get up the hill. I'm trying to figure out the cheapest way to swap gears. I found a 14 bolt SF rear end out of a 1990 3/4 ton truck with 3.73's. Not sure what all would be involved to make it work, but it seems I would be money ahead by putting the stronger rear end and upgrading gears at the same time. I would then just have to swap the gears in my front 10 bolt. I plan on staying with 33's and primarily use it on the street and want to use it for a hunting, camping, fishing vehicle in the mountains. My other option is to upgrade the gears in the current 12 bolt to whatever I want. Any opinions on the best gear for my intended use?

 

[Deuling]

3.73s

 

[Greg72]

Just regear your stock axles... For your intended use it would be a waste of money to do some elaborate axle swap.

3.07 to 3.73 might not be dramatic enough to satisfy you. I'd consider at least 4.10s and maybe deeper. Check out the gear calculators and see where your highway RPMs end up with a few combinations. Deep gears will really wake up your truck.

-G

 

[80' 427]

4.10s or 4.56s

 

[80' 427]

also you have a 44 front if it is stock.

 

[70jimmy]

Using newer model gear would require moving the spring perches and probably shock mounts on the rear axle. When I did the swap my front spring perches were fine but I did have to move shock mounts front and rear and rear spring perches. When I did it I pointed the pinion at the T Case.

I would keep my eyes open on the for sale boards. For your use a 10 bolt or 44 front would be fine. My swap gave me lockers front and rear and 4 wheel disk brakes along with hydro assist steering.

There is always someone out there upgrading to rockwells and wanting to get rid of old axles.

put in gear calculator in your search screen on here or the internet and figure what RPM you want for cruising on the highway and maybe bump one. I think you would be happy with 4.10 with 33's but if you want more power 4.56 is nice but might rap up a little on the road.

 

[nocok5]

also you have a 44 front if it is stock.

Thanks for the responses so far. My Blazer has a ten bolt out of an 84. Did this swap for the disc brakes. Would the ten bolt front and twelve bolt rear need a new carrier to swap to 4.10's. Found a 14 bolt sf out of a 1990 Chevy truck with 3.73's that is 6 lug. I want to keep my Ralleye wheels regardless of what I do. I also plan on keeping the 350 transmission since it was just rebuilt.

 

[ashman]

I plan on staying with 33's and primarily use it on the street and want to use it for a hunting, camping, fishing vehicle in the mountains.

with that said, I would say 4.10 would be about perfect.

 

[clandr1]

I put 4.10's in my '89 (350/700/33") back in July and the gas mileage increased dramatically on the highway. It no longer hunts in and out of OD/lockup, and it has a little more guts around town.

However, your TH350 tranny does not have OD if I remember right, so 3.73's might actually work pretty well given the anticipated higher RPMs on the highway.

I attached the chart I used in making my decision: make sure you note that with your non-OD tranny, the RPMs will be slightly higher, so 4.10's might be just the ticket.

I would look around for some 3/4 ton axles with 4.10's already in them and do an axle swap, unless you know how to regear yourself. It is far more cost effective than regearing stock 1/2 ton axles.