The Ford Barn - T170 help

The Ford Barn (https://www.fordbarn.com/forum/index.php)

- Early V8 (1932-53) (https://www.fordbarn.com/forum/forumdisplay.php?f=4)

- - T170 help (https://www.fordbarn.com/forum/showthread.php?t=341662)

I picked up 2 rts t-170 trans I can’t remember which two I have at the moment but I’m running 3.54 gears and 265/75/r15’s (30.6) going by the calculator i would be running 2500rpm at 65mph in 1:1. I am currently only running it up to 50mph at 1900rpm. Which of the 3 overdrive ratios would you recommend 26.7%, 41.1%, 37.9% I’m just worried to pick the highest overdrive if it is going to be bogging with the higher 3.54 gear. My goal is to not be screaming at 60-65 running an 8ba in 37coupe currently have the 60hp trans

Who is doing your trans Tube drive shaft

John

I have a 1938 coupe

John

Be aware that overdrive % gets advertised in two different ways that are not equal.

First: reduction of the input shaft. This is how the Borg-Warner overdrives and most other overdrives are calculated. For example, the common R-10 Borg-Warner unit has a ratio of 0.7 to 1. This is listed as a 30% overdrive since it will drop your engine rpm by 30% at the same road speed. To get the gear ratio from this method simply subtract the overdrive ratio from 1: 1 - 0.3 = 0.7.

Second: increase of the output shaft. This is how Mitchell and the T170 are advertised. For example the "41.1%" overdrive T170 has a ratio of 0.7087 to 1. Reversing the ratios this becomes 1 to 1.411 (see what was done there, 0.7087 divided by 1...). I am annoyed at this method since I think it is done for advertising purposes rather than for direct understanding. To calculate the gear ratio with this method you divide 1 by 1 plus the overdrive ratio: 1 / (1 + 0.411) = 0.7087.

In case you are not aware of it already there is a nice website with the T170 gear ratios here: https://www.fordgarage.com/pages/TremecT170FT.htm

I prefer the first method since it gives you a direct understanding of the actual gear ratio.

The best ratio for you depends entirely on your engine, the area you will drive the vehicle, and what you want. I recently ended up with 3.50 gears in my 53 sedan behind a stock 6 cylinder and an R-10 overdrive. This is a fairly gutless combination, but works surprisingly well in the flatland of Texas where 80 mph down the highway is good. Around town is no fun.

The lower 26.7% would be preferable but they are getting harder to come by since most folks wanted them. The T170 has been out of production a long time and it wasn't produced very long so this makes parts harder to find as the years go by. They are out there but you really have to do a lot of searching unless you get lucky.

I’m taking the banjo I bought back to open drive I have the Pete and Jake’s ladder bar setup already also. I did buy a trans to TT adaptor plate but don’t want to mess with the tail shaft if I go open drive line since t-170’s are hard to come by and parts it would allow me to do a t-5 in the future if I needed to

Found out one of my trans is a BS undesirable gearing, a BV Which is the 27% better highway cruising which is what I’m after time to order a rebuild kit and a Granada clutch and get ready to put it in this winter��

With your tire diameter and rear axle ration you don't need overdrive to go 65 mph. A good running 8BA without balance issues will run well above 2,000 rpm all day long. I try to gear my cars for approximately 2,700 rpm at maximum cruising speed. Your combination with 1 to 1 transmission high gear already goes 69 mph at that rpm. As fun an academic exercise as it may be, you are solving a problem you don't have.

I agree with the above. I have found an 8BA has a "sweet spot" between 2300 and 2700 RPM.

In need of a cluster gear, input shaft and OD gear for C ratio. Thanks for any help or guidance

I agree with 38 coupe on your current combo; if your engine is stock in good repair you should be fine on flat ground (where you live). With the T170, you can drop out of O.D. on a hill and not lug the engine and your first gear is synchronized so dropping into first for a "roundy- round" is no big deal. If you're planning on an engine rebuild you can up the available torque and maybe not down shift on Brown County hills. JMHO

Bought one many years ago and could not find a local source locally to modify the torque tube and I moved on to other projects.

Found this site which appears to fully document the T170:
https://www.fordgarage.com/pages/TremecT170FT.htm

Thanks Barnfind
I am running a T170 in my 36 and am having some synchro issues
This will help me find a cure

@Johndee138 - I could probably be persuaded to part with mine for what I paid for it if you want to take a bit of drive.