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#580391 Sun Oct 04 2009 05:54 PM
Joined: Oct 2000
Posts: 804
M
Shop Shark
Ok, I thought I posted about this but couldn't find the thread. If I did, I'm sorry to post it again.

I have a buddy with a 51 that has a 55 passenger car rear (with 3.70 gears I believe) and a 59ish 235 that is stock.

It now has a compound low 4 speed.

He wants to be able to drive it down the freeway at 65. Right now it is winding it's poor guts out and we want to do something to raise the overall gear ratio.

Would the best bet be a T-5 and if it is is there a thread on installing one?

Or would simply changing the rear end to a 3.00 or something be better. I am thinking the poor little six won't have the power to pull a sick dog out of an outhouse. Not unless you use the first gear in daily driving which would be ridiculas being it has no synchros.

What are your thoughts?

Brian


1948 Chevy Pickup
Chopped and sectioned
owned since 1974 when I was 15.
Joined: Sep 2006
Posts: 2,960
D
Shop Shark
If the 55 rear came from a powerglide model it's a 3:55. In any case I'd go with a T5 just because I read where most are quite pleased with the switch. Technical help is in the Tech Tips and also on the Inliner site Tech pages.

Last edited by DrewP; Sun Oct 04 2009 07:21 PM.

Drew
Joined: Jan 2000
Posts: 2,211
J
'Bolter
Also, since you are already using open drive rear end the T-5 swap will me much easier. The 3:55s or 3:70s would both be super with the T-5 od. The T-5 is the best mod I've made in my pickup, just shop around for the right one. Also contact www.stoveboltengineco.com he had some rebuilt units earlier in the year.


It's easier to get forgiveness than permission!
1946 1/2-Ton Chevy [stovebolt.com]
1953 Chevy 3/4-ton Factory Stakebed [stovebolt.com]
Joined: Oct 2005
Posts: 1,318
F
Shop Shark
Just a suggestion.....if you decide to go with a T5 bear in mind that the S10 boxes come in 2 basic ratios and if you plan on running a 3.70 R&P you'll want the .72 OD. You'll find the .72's behind the 2.8L V6's while the .86 OD's are generally found behind the 4 cylinders. The S10 .86 boxes work best with the lower number R&P's....such as the 3.08's and have a 4.03 1st gear which makes for very quick shifts into second. The .72 boxes are a bit higher with a 3.76 1st gear and give you a little additional time in 1st gear.

A third option for a T5 is from the Camaro's with a 2.95 1st gear and a .63 OD. However, to use this box in your 51 truck you'd need to unbolt the Camaro tailshaft which puts the shifter back in the middle of the front seat and bolt on an S10 tailshaft. The speedo drive gear has to be relocated further forward.....sounds a bit technical but it really isn't that difficult of a mod. I've documented the mods and installations to both the S10 and Camaro T5's in my Truck and Street Rod Webshots albums. My current project vehicle is running the hybrid Camaro T5 behind a built SBC with a 3.73 diff.

After 10K miles in my AD truck with the S10 .72 T5 with most of it on the open road, I can attest that it's the best modification I've made. Being able to cruise well within the 235's torque band has opened up a whole new dimension for my old truck.

Dave





Webshot "Tips and tricks" and "Shoebox" Photo Albums

EXPERIENCE is the best teacher...but it gives the test first...and the lesson afterwards.

"What this generation tolerates...the next will embrace"
Joined: Aug 2004
Posts: 1,068
H
Shop Shark
Also, I wouldn't suggest a 3.08 ratio for a 235. It literally does not have the power to pull those gears. You'll slow down on the slightest incline. You can do those gears if you can improve your power significantly. A 292 would be a great swap. Plus it would also be able to take that T5.

Joined: Oct 2000
Posts: 804
M
Shop Shark
Thank you so much guys, I have printed this all out along with the Tech Tips and given it to him.

No more thinking, just put the T-5 in it and have fun!

Brian


1948 Chevy Pickup
Chopped and sectioned
owned since 1974 when I was 15.
Joined: Oct 2005
Posts: 1,318
F
Shop Shark
A 3.08 with the S10 T5 with a .72 OD transmission WOULDN'T be the correct choice for the 235. However, if you crunch the numbers with an S10 T5 with a .86 transmission from behind a 4 cylinder, you'll find that you'll be at 2030 rpms at 65 mph and can drop down to 45 mph without a downshift. A decent choice.

http://csgnetwork.com/multirpmcalc.html

That's why I pointed out the importance of knowing WHICH S10 T5 OD ratio transmission to purchase to make your setup stay within the torque curve. If the tag is missing from a T5 transmission you'd better be ready to spin the tailshaft to positively identify the correct OD ratio.

If Brian is truly running a 3.70 R&P the S10 .72 transmission or the .63 Camaro hybrid would be the correct choices for his 235. If he were running an S10 .86 OD transmission he would be turning up 2684 rpms in 1st gear at 15 mph and 2482 rpms at 65mph in 5th gear......fairly deep into the torque curve and only 400 rpms better than the stock 1:1 transmission. With the S10 .72 OD he'd be turning 2078 rpms at 65 mph and getting a few more mph out of 1st (3.76) gear without "winding the guts out of it."

In reality, the Camaro T5 with the .63 OD would help him out with a 2.95 1st gear and would let him cruise at 65 mph at 1818 and 2000 rpms at 70 mph. However, you may wind up having to buy an S10 donor transmission (either .86 or .72) to get a tailshaft to complete the shifter relocation.

The whole point of my post was to point out how critically important it was to properly ID the T5 transmission before you buy it. An S10 .72 T5 WILL NOT work with a 3.08 Ring and pinion but will maintain your 235 in the torque band with a 3.42, 3.55 or 3.73 R&P. It would also let you cruise at 65 mph at 2190 with a 3.90 open-driveline (55 1st and up) diff. The key is to lock in on staying well within the torque band 1500-2300 rpms.....that's where your stockish 235 will purr instead of scream.

Dave

BTW...I used a 28" tall rear tire for these calculations.


Webshot "Tips and tricks" and "Shoebox" Photo Albums

EXPERIENCE is the best teacher...but it gives the test first...and the lesson afterwards.

"What this generation tolerates...the next will embrace"
Joined: Aug 2007
Posts: 1,910
S
Grumpy old guy playing with trucks, cars, and boats
I suggest the Camaro hybrid, or use one from the Astro as the gear ratios in the Astro are a better spread yet.


The problems we face today can not be addressed at the same level of intelligence we were at when we created them - Albert Einstein Or with the same level of $ - Me
Joined: Oct 2000
Posts: 804
M
Shop Shark
Thanks again guys for all the help. He is well underway getting this bugger out on the highway.

Brian


1948 Chevy Pickup
Chopped and sectioned
owned since 1974 when I was 15.

Moderated by  KCMongo 

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