REAR END upgrade question.

[junglefire]

I have a '66 C10 with a 350 crate motor..
when i get on the highway and get up to 55-60mph, i feel like the engine is revving high and pretty much can't go much faster. i'm sure my gas mileage suffers here too. i don't go on the highway often, but when i do..ugh.

is there a rear end i can swap out. what gear ratio should i be looking for?

just wanna get up to 60mph with out over revving.. i have a 3 on the tree tranny.

[blackedoutharley]

There are several ways to improve the freeway performance in your truck. The easiest way is to install a larger diameter rear tire.

Most people change the gears in the rear end to a lower (numerically) gear such as 3.42:1 vs. the "normal" 3.73:1 or 4.11:1 ratio normally found in our trucks.

You could also buy a rear end that has 3.08:1 gears. The only 'true' way to tell the actual gear ratio is to pull the rear cover and do the math.

Not knowing what gears you currently have makes it impossible to make an accurate recommendation.

What rpm are you running at 60 mph? (I am guessing you don't have a tach installed). Have you confirmed that the speedo is correct?

[jimmydean]

Originally Posted by blackedoutharley

You could also buy a rear end that has 3.08:1 gears. The only 'true' way to tell the actual gear ratio is to pull the rear cover and do the math.

I went this route and gained disc brakes as well. I wanted a posi unit, but this will work for now.

[junglefire]

yeah no tach..
and not sure of the speedo, but everything else on the dash works.
and i see everyone passing me easily on the highway. so i'm guessing it's right.
and it def. doesn't wanna cruise any faster.

i'll check the rear end and see.

if i go with a smaller ratio.. is this a bolt on mod? will i need change anything else out?

[brokenspoke]

change to a T-5 transmission

[blackedoutharley]

Originally Posted by jimmydean

I went this route and gained disc brakes as well. I wanted a posi unit, but this will work for now.

I was referring to a 12 bolt rear end out of another coil spring truck as a bolt in replacement.

Originally Posted by junglefire

if i go with a smaller ratio.. is this a bolt on mod? will i need change anything else out?

Use a gps unit to confirm speedo. It is not a bolt in and I highly recommend that you take it to a shop that specializes in differentials have the gears set up properly.

[jimmydean]

Originally Posted by blackedoutharley

I was referring to a 12 bolt rear end out of another coil spring truck as a bolt in replacement.

I had a tough time finding a 5 lug 12 bolt coil rear that wasn't crazy priced. For less than what I would have paid for a 5 lug drum rear, I got a 10 bolt (8.5 ring) disc rear.

I was planning to run discs, anyway. But the savings was incredible. I would have to weld on perches to any non-coil rear.