T170 help

[Dyingbreed]

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

[deuce lover]

...

[1956 ford]

Who is doing your trans Tube drive shaft

John

[1956 ford]

I have a 1938 coupe

John

[38 coupe]

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.

[rotorwrench]

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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.

[Dyingbreed]

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

[Dyingbreed]

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��

[38 coupe]

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.

[tubman]

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

[Mcgregor]

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

[ActionYobbo]

Input shaft

https://www.transmissionpartsdistrib...pAMSfSLD1p0F_Y

[joel]

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

[barnfind]

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

[johndee138]

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

[barnfind]

@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.