what is a good axle gear ratio

[66clow]

I have a 66 c10 with a 327 engine with a 3 speed. need to change the rear axle gears so i can keep up on the highway. I have 4:56 gears and run 60-65 max, any faster I will blow up the engine. What is a good all around gear ratio to run 70 comfortably but not totally lose my pull from starts?

[ole dollor]

i would say try a 308, i have a 276 in ole dollar and its a 292 six, with a granny 4 speed , went from 373 to 276 and i am at 2000 rpm at 67 mph. i was at 3000 rpm at 70 mph....and i did not like the rpm...or at 2000 rpm i was at 50 mph. did not like having to drive at 50 mph. i am getting over 18 mpg with this setup , just my 2 cents worth, hope this help you out a little.....

[Coboyle04]

I'm in the same situation just blew up an LT1 motor my dad put in an old 72 Pu, I couldn't hear the transmission winning. Mine 465. At least I want a 373 but a 342, 323 308, or 273 would be a dream
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[Coboyle04]

Is it an eaton rear end. If so I think the best you can do is a 410 unless you do an axle swap. I think an axle swap us cheaper anyhow
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[3rdGen.c10]

from my experience 3.08 is a little tall to expect a good pull from a dead stop out of. i would do atleast a 3.42

[mud.man.rj]

The 3.42 is a real nice ratio as mentioned, good on highway and good around town too.

[jocko]

66clow, the real question is whether or not you plan to retain the 3 speed. If so, then I agree with the 3.23 or 3.42 crowd. If there's a possibility of an overdrive trans in your future (say a T5 if you stay manual or 700R4 if you switch to an auto), then I'd consider a switch down to 3.42 or 3.73.

EDIT - btw, 3.08 and 3.73 is what was available from the factory in 66, so either will work, but you'll severely sacrifice low-end grunt for hi-speed cruising comfort with a 3.08. And that might be ok. All depends on your goal - and if it is truly highway driving and you are going to retain the 3 speed, then a 3.08 will work - BUT, since you have to change to get there, a 3.23 (or 3.42) might be more workable.

[oem4me]

I have heard that unless another ratio was specified, the 373 was assigned by default. A middle of the road ratio to suit the widest needs.

[jocko]

Originally Posted by oem4me

I have heard that unless another ratio was specified, the 373 was assigned by default. A middle of the road ratio to suit the widest needs.

That's correct oem, 3.73 standard and 3.08 was the option. I have 3.08 on my SPID because it wasn't standard. Ironically, someone swapped in a 3.73somewhere along the way But I agree. Middle road best. When I had the stock 3-speed, the 3.73 seemed like a pain on the highway, but I thought the 3.08 would've made low end too painful also.

[awbrown]

My 63 has the 3.08 and I still think it turns up pretty good going down the high way ,of course no body drives under 70 mph here in the motor city,so I guess it depends on if you are going to swap in an overdrive trans , or run a taller tire... My other truck , that was my DD when I lived in Maine had 3.73 and I never showed it any mercy 65 0r 70 mph was normal and I just let it sing...

[66clow]

Thanks for all the info. Think ill try the 3:42 for the all around. Here in Atlanta all the roads are 65-70.plan to keep the 3 speed for the coolness. No plans for drag racing so I can sacrifice some low end.
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