The Stovebolt Site Forums The Shop Area The HiPo Shop trying to lock in a plan

I have a blank canvas of a 1956 3100 with a choice of the original 235 or a 261, the original 3 speed or a T5 (1st 3.76, 2nd/3rd Unk and OD .72) , and a ford 9 inch with 3 50 gears or the original rear. 3.90 or 4.11 I do not know what it is.

the logical part of me says run the 261 with the T5 and ford 9 inch.

Would this be a good combination for a daily driver, In town and in a small city like Kansas City?

The T5 and a 3.90 gear is a great combination for a 261. I know a guy that pulls a 19 foot Camper with this setup, no issues at all.

I ran a 235 with a 4.54 Dana, sm420, then M20 car tans. Then same 235 with 3.73, then a T5 with same 235.
Installed 261, ran it a couple years before going to 4.10 axle a couple years ago.
That seems to be the best setup for me. We have hills around here that are refered to as mountains by some so your best ratio may differ.

Rock - You truck is most likely to have the 3.90 rear axle as that was the standard regular production equipment coming from the factory. The 4.11 was installed in trucks equipped with the Regular Production Option (RPO) 315 - 3 speed overdrive transmission in the 3100 and 3200 trucks.

The proof is in the stamped characters on the left front face of your 3100/3200 differential pumpkin. The letters "AF" indicate 3.90 and "AG" indicate the 4.11 gear set.

I would second Craig's (TUTS 59) recommendation to use the 3.90 with T5 and the 261. But, that is dependent on what the T5's final drive output is. A T5 OD output of around 0.87 will work best with the 3.90, where a 0.76 T5 will work best with the 4.11 from all the research through other folks setups I've read.

In fact my '51 is slated to get a 261 with the 0.87 T5 and 3.90 rear open drive axle treatment at some point in the future.

Good information thanks. The OD in the T5 is .72 , so I will run it while I keep my eye out for one with a lower OD.

If I'm doing the math correctly a 0.72 OD output coupled with a 3.90 gear ratio leaves you with an effective final drive ratio of 2.808. It's a really significant change in engine rpm from the straight 3.90 gear with 4th (1.0) output with the T5, to 2.808 in 5th (0.72) output. That's really in the highway driving range and the 5th gear won't really hit the 235/261 power band sweet spot in city/non-highway driving.

You'll be fine in the lower 4 gears for in city driving with the 3.90 and this T5 though.

A note on making this change - be sure you are giving your other systems of your truck like brakes and steering a thorough going through and refresh or upgrade. Getting things rolling at higher speeds mean you have to be sure your can safely steer/stop as well, for the benefit of yourself and others on the road.

+1 on Dan's advice- - - - -back in the dark ages when I was teaching high school auto mechanics, my advice to all my students was "I'll be glad to help you make your car go fast- - - - -but we're going to be sure it stops and steers right first!" Most of them hadn't really considered that!
Jerry

Need the Whoa to match the Go.