Rear end ratio?
 

Any thoughts on what a 61 c10 3/4 ton 4 speed with granny would have for a rear end gear ratio? Haven't bought the truck yet just trying to figure what trans I can replace with . Leaning toward a 700r.

Re: Rear end ratio?
 

Do you know the gear ratio?

Does it currently have a 4 speed or auto?

Re: Rear end ratio?
 

I don't know the rear end ratio. That's what I was asking. The truck is a 3/4ton 4 spd. standard with granny low. I want to put auto in but not change the rear end. I want to be able to drive to town and not do 3000 rpm at 50 mph. Any thoughts on what the rear end ratio would be?

Re: Rear end ratio?
 

Here is the chart on rear axle codes. The stamp is on the top of the drivers side axle:
http://qptwaq.bay.livefilestore.com/...%20Axle_ID.jpg

Re: Rear end ratio?
 

If it's original, per the Rod's chart it's a 4.57 ratio. A 700R4 trans has a .7 ratio OD, so that would give you a 3.2 ratio in OD. That's a respectable drop in RPM! The 700 has a really steep first gear with a big drop in RPM from 1st to 2nd. A lot of people use a 200 for this reason. I think that I recall that a 200 needs a bit of beefing up if it's going to be used hard, though.

Re: Rear end ratio?
 

Thank you Rocknrod looks like they were all 457 ratio. Probably not too good to cruise around in even with a 700r. So probably a rear end change, so it will be more user friendly. Just trying to figure out what I will all need before I go look at this truck.

Re: Rear end ratio?
 

I also have a 200r but I want to kind of use this truck for hauling a car and trailer once in a while. I didn't know if the 200r would get it done without dumping a bunch of money in it. Most of the use will just be driving around. Thank you Mr.Steve.

Re: Rear end ratio?
 

You could put an nv4500 5 speed in it since it’s already a manual.

Or you can get a 14 bolt and Captn Fabs mounts and swap that out before your trans

Re: Rear end ratio?
 

This is the route I took with my 64 C20. I swapped the original rear axle out with a 14 bolt with 4.10 gears and also put in a NV4500 from a 98 c3500. Hope to get it running and driving this summer.

Re: Rear end ratio?
 

Your first post says '61 C10 3/4 ton. A C10 is a 1/2 ton with 6 lug wheels. A C20 is a 3/4 ton with 8 lug wheels. Additionally a '61 will not be a C series, it is an Apache 10 or an Apache 20. The C series did not start until 1962.

Re: Rear end ratio?
 

I didn't notice this Captain till you pointed it out. It is an Apache 20 eight lug wheels. I have been in half ton land too long. Thank you

Re: Rear end ratio?
 

When you say 14 bolt rear end? Not real up on this 3/4 ton stuff yet. Would that be a bolt in? What did they come in? Maybe I could do the rear end and leave the old trans for now. Thanks for the info

Re: Rear end ratio?
 

Some 67-72 20 series trucks with V-8 & automatic had 4:11 gears in them & the 3rd member fits your housing. They can be hard to find though.
George

Re: Rear end ratio?
 

It won’t be bolt in, but Captn Fab has trailing arm mounts that you can use after you remove the leaf spring mounts.

Re: Rear end ratio?
 

I don't know about the interchangeability of the rear ends, but you could probably find a Dana 60 from a big block truck that has a 3.54 axle ratio. It would have leaf spring mounts, most of the time. I see that some have coils.

Re: Rear end ratio?
 

The 14 bolt was available in both the 10.5" full floating and the 9.5" semi floating configuration starting in 1973 in the C/K20's and 30's up into the 2000's somewhere when GM went to the AAM differential. So there are tons of them out there. Even if you do find a Dana 60 from a '67-'72 truck, the trailing arm mounts will still have to be moved to bolt up to the trailing arms in your '61.

Re: Rear end ratio?
 

I'm not all that familiar with these year trucks. Did the '61s only come with coils?

Re: Rear end ratio?
 

Thank you guys for all the come backs. I am going to look at the truck this weekend i hope weather permitting. Now at least i know what to look for. I have a 70 gmc I have that's been apart 6 years and i just want a driver. That I can putt around in chase parts, go for coffee. Getting ready to retire so hopefully should have lots of free time. Thanks again!

Re: Rear end ratio?
 

Captain , you burst my bubble again ! I bought a 72 frame with a dana 60 with 4:10 s and thought i understood it would be a direct bolt in.

Re: Rear end ratio?
 

The '60-'66 Chevy 2wd came standard with trailing arms and coil springs. The '63-'66 GMC's came standard with leaf springs in the rear.

Re: Rear end ratio?
 

Back in the '60s, I worked for my BiL on the weekends on a fleet of trucks used by a company that installed central heat and air. I'm certain that they were all Chevies; I don't recall any D-word or F-word trucks, and no GMCs, either. I also don't remember what they had for suspension, sad to say. If it got shocks, for example, I just put 'em on. I was just a kid, I didn't order the parts. Their fleet started at about '55 or so, up to new stuff for the years I was working there- '68 until '72. I DO remember sitting on cardboard for the ride home after putting rod and main bearings in a '56 Chevy truck from underneath. I had black drain oil over pretty much all of my skin. Guess I'll never rust. :lol: Too bad I didn't pay more attention to them back in the day. I'd be a goldmine of information :shrug: