1961 - 1966 F-100 & Larger F-Series Trucks Discuss the Slick Sixties Ford Truck

Overdrive for a T-18?

Old 07-07-2005, 06:19 PM
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The bottom gear in the t-18 is more like 6.28 There were close ratio t-18 trannies, but I think they were not ever in Ford trucks, but instead in IH Scouts.

Here are the ratios that I have usually seen mentioned:

1st 6.28, second 3.09 3rd 1.68, fourth 1.00 These are the "wide"

The close ratio tranny has:
1st 4.02 second 2.41 third 1.41 and 4th 1.00

The bottom gear in a close ratio t-19 is much more useable as it is much closer to 2nd than the wide ration 6.xx first. Moreover, the syncro first become much more interesting city driving, where downshifting is more frequent.

There is no magic to an overdrive -- it is all in the distribution of the various gears. I admit that the jump from 4.02 to 2.41 is still a bit much in the close ratio. But better than the 2x change seen in the wide ratio.

As long as the distribution is good, you can adjust your final RPM by swapping the right rear differential in.

Just trying to find a cheaper alternative.....
Old 10-01-2018, 01:19 PM
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don't know about 3500 I have the same setup in my 66 I think it runs around 3000 at 70 I have done 80 in the truck however and still had petal travel and didn't hit my mid rev limiter
Old 10-01-2018, 05:52 PM
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Originally Posted by brider View Post
Is/was there a bolt-on overdrive unit for the T-18 Ford tranny?

Mine is in my '66 F250, and it occured to me that waaaay back in the 60's the US highway system speed limit was 70, so there was probably a market even back then for an effective overdrive system on these trucks.

Any body run across one?
Here is what I did with my 300ci T-18
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