Advice on 61 rear end solution

[SMR]

Hello everyone, looking for advice on making my recently purchase 61 LWB C10 more highway friendly. I’m running the stock 283 motor (with edelbrock 1403 carb), automatic 2 speed powerglide, 29” tires and , what I’m told, is either a 3.92 or 4.11 rear end. I’m pulling about 2k rpms at 40 mph. I would like to be able to travel at 65 or 70 without having the motor work so hard. I understand that I can switch out the rear gear set to a 3.38, which will enable me to drive at higher speeds at more appropriate rpm levels. My question: Will this solution be sufficient to achieve my objective and are there other concerns I should be made aware of that may be the result of making this change to the drivetrain. My second question: Is there better solution that would be on par with the cost to switch out the rear end gear set?

Your help is greatly appreciated

[hop sing]

Originally Posted by SMR

Hello everyone, looking for advice on making my recently purchase 61 LWB C10 more highway friendly. I’m running the stock 283 motor (with edelbrock 1403 carb), automatic 2 speed powerglide, 29” tires and , what I’m told, is either a 3.92 or 4.11 rear end. I’m pulling about 2k rpms at 40 mph. I would like to be able to travel at 65 or 70 without having the motor work so hard. I understand that I can switch out the rear gear set to a 3.38, which will enable me to drive at higher speeds at more appropriate rpm levels. My question: Will this solution be sufficient to achieve my objective and are there other concerns I should be made aware of that may be the result of making this change to the drivetrain. My second question: Is there better solution that would be on par with the cost to switch out the rear end gear set?

Your help is greatly appreciated

I have a 61 too w/ the 3.92 or 3.90 ,,I ran a 700r4 cost me about 700 w/loc up ,and I can run at 70-75 and my rpm is at 2350 ,its like a hole new truck ,but u also need to cut own driveline ,and adapt ur p/g cross member which is easy ,I like the first gear of the 700r4 don't like 2 so much but you'll get a good take off

[SMR]

Hello hop sing ..thanks for sharing your setup...it may be the way I'll have to go if the rear end gear change isn't viable. Hoping someone can give me some feed back on the option of just the rear end change and effects on rpm and overall expected performance.
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[luvbowties]

Originally Posted by SMR

Hello hop sing ..thanks for sharing your setup...it may be the way I'll have to go if the rear end gear change isn't viable. Hoping someone can give me some feed back on the option of just the rear end change and effects on rpm and overall expected performance.
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Dunno your restrictions on tire height, but just for info, using a 35-inch tire instead of a 29-incher would make the engine "see" a gear reduction equivalent of 29/35 = .829; or make a 4.11 'look' like a 4.11 X 29/35 = 3.41. Along the same line, it would drop rpm's at any given speed the same amount--like from 3000 to 3000 X 29/35 = 2486. Other heights would be similar and proportionate in reductions.
Sam

[AcampoDave]

The tricky part is the 2 speed powerglide. I don't know what the ratio is on first but it may be rather steep. Going with too much rear end gear could really effect your take off from a stop. Many squarebody trucks came out with 340's and some had 308's which is what I run with a stock 283 and 3 speed clolumn shift. The sqarebody rear end fit my fleetside well, but is a touch wider than stock. It is 5 lug which was desireable for me but 4x4's are 6. (I have a friend with a Blazer rear end and 308'S and he likes it). It is a bit of work to transfer the mounts and all, but if you can cut and weld you can do it. Pm me if you want more details on how I installed mine.

[SMR]

Sam thanks for the information on a tire change to achieve ratio change. Not sure if 35" tires will fit or what it would cost to which out rims and tires to get me to the targeted rpms. Any experience with fitting 35" tires on the 61.I have 2" dropped spindles in the front and 3" dropped springs in the back.
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[SMR]

Originally Posted by AcampoDave

The tricky part is the 2 speed powerglide. I don't know what the ratio is on first but it may be rather steep. Going with too much rear end gear could really effect your take off from a stop. Many squarebody trucks came out with 340's and some had 308's which is what I run with a stock 283 and 3 speed clolumn shift. The sqarebody rear end fit my fleetside well, but is a touch wider than stock. It is 5 lug which was desireable for me but 4x4's are 6. (I have a friend with a Blazer rear end and 308'S and he likes it). It is a bit of work to transfer the mounts and all, but if you can cut and weld you can do it. Pm me if you want more details on how I installed mine.

Dave my concerns as well. Don't need super fast out of the gate.. But don't want a dog either. Got to believe someone out there has tried 3.38 gears with a 2 speed powergulide. Thanks for the info..it's good to have options.
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[luvbowties]

Originally Posted by SMR

Sam thanks for the information on a tire change to achieve ratio change. Not sure if 35" tires will fit or what it would cost to which out rims and tires to get me to the targeted rpms. Any experience with fitting 35" tires on the 61.I have 2" dropped spindles in the front and 3" dropped springs in the back.
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No experience with them--just picked a number at random to demonstrate what they "could" do.
Sam