Swap the tranny or the rear diff??

If it were my truck, I wouldn't change the 3/4 ton capacity, or the 8 lugs. Unless I wanted to change the front hubs too and rim size and on and on and on.
Most 3/4 ton late model rears are going to have a numerically higher gear in them any way. 3.7x and up.

http://www.richmondgear.com/101032.html

You can play around with that and see your combo go from 3300 rpms @65 down to 1825 @ 65 with. 37x and OD.

gotta watch the power band of your particular engine , running it below the power band isn't going to help you any.

 

did not know that. never seen one. half ton was torquetube? learn something new evreyday. thanks

 

Good info here, thanks!

 

FWIW, easy tip to find that 3.08 or 3.23 - check the glovebox RPO sheet for GU4 or GU5. 4 is 3.08, 5 is 3.23.

 

I think the lowest gear you could get in the up to '72 with removable center section is 4.10 and 4.11. Big block only trucks got the bog Dana rear(non-removalbe) and you could get a 3.54 gear. I have two of these a '70 and a '71. 3.73 was only a half ton gear as far as I know. your easiest bet is as said maybe a van 3/4 ton from 70s or 80s, they might be short enough and get you a decent gear. 2004r would be the easiest trans swap, same length driveshaft, you just have to move you crossmember back as the mount is right on the ass end. this assumes you have a short tail th350...

 

I would keep the 8 bolt FULL FLOATING rear end too. Just do some research and find out what ratios were available on 67-72 Chevy 3/4 ton trucks. The carriers were the same for 3/4 tons from the early 50's up to 72, trust me I had a 51 GMC 3/4 ton, and had the rear end rebuilt, all with 72 Chevy parts. I would think you might be able to find a 3.70 or thereabouts ring and pinion for your truck.

 

Not for nuttin', but here are a couple of pictures...

 

I was talking to a chevy guy tonight and he has a 1980 Chevy pickup 4x4 with that wheel pattern.I would guess it must be able to do 70 mph.I also was wondering if the spindle on front is the same as 1/2 ton could go that route to match wheel.Think they were 6 bolt.

 

my friend has a 53 1 ton and i know what they mean when they say it rides like a truck . we swapped out the 1 ton 5:13 rear for a 9" ford with wheel adapters to fit the 8 lug wheels just welded on the spring perches not to tuff ,now parts are simple to find and gear ratio's are easy to find also. as far as the trans a 200r4 is supposed to be a bolt in replacement for a 350. i would do both it makes a huge difference if your idea of highway driving isin the 70-80 range

 

my friend has a 53 1 ton and i know what they mean when they say it rides like a truck . we swapped out the 1 ton 5:13 rear for a 9" ford with wheel adapters to fit the 8 lug wheels just welded on the spring perches not to tuff ,now parts are simple to find and gear ratio's are easy to find also. as far as the trans a 200r4 is supposed to be a bolt in replacement for a 350. i would do both it makes a huge difference if your idea of highway driving is in the 70-80 mph range

 

An article, so you don't have one or know much about them? Alot of people replaced them with a TH350 because there cheaper to build. Talk to a good trans guy, and he will disagree with you about a 200-4R. A regular 200 was known for failure which gave them a bad name.

 

Nope, not in stock form, and built they are both more than strong enough. The 200 has a better gear spread and uses less power. But nice try..

lol, x2

 

I have talked to transmission guys, and I have both types of transmissions...

Here ya go....

http://webrodder.com/article.php?AID=426&SID=6&CID=17



I never said they couldn't be BUILT to handle more HP...

 

I'd just do a OD trans..3.19 end result with probably 29" [at least?] tires = 2585 rpm at 70 mph; doubt if the engine would be any happier, don't think you have enough power to run less rpm..Have enough power means the truck is [well] over 4000 lbs and just because you can gear and overdrive the hell out of it doesn't mean it will be better, too much and your gas milage will suck..What does the truck weigh?

 

Aww he's so cute... if you believe what Doc writes you should build a Nailhead with his article on them. LOL...

 

I would concentrate on the rear end gears keeping in mind that you won't want too high a ratio if you do decide to go with the OD trany later. I doubt that with a 6 you are worried much about launches. With the TH350 I would think a 3:20 gear would be about right and would be a reasonable gear for an OD transmission. If you are willing to put a Ford 8 or 9 inch rear end in it you would then have the benefit of a removable pumpkin which makes gear ratio changes easier.
Richmond Gear has an online gear calculator that you can use to play around with different ratios, tire sizes ,etc to see what you engine RPM will be at various road speeds. As an example I run a 700R4 with 3:55 gears and 235-70 15 tires. With the converter locked up and the transmission in OD , at 65 mph my engine is turning about 2200 RPM.

John

 

By the way, if you are lucky and happen to have the 9 inch tail shaft on your TH350, then the length of the transmission is within 1/16 of an inch of the 700R4 ( non-Corvette tranny ).