T18 Identification

Does anyone know how to externally identify a 4-1 T18 from a 6-1 T18?

 

https://www.novak-adapt.com/knowledge/transmissions/manual/t18-t19

Novak's guide is pretty good, although from what I've gathered on this forum the best bet is to open it up and verify.
Found my dad's T18 using the Novak guide as a reference, and shifting it into first and counting turns if I remember right.



Been a few years.

 

Are you able to put it in first and count rotations?
(Only applies if removed from vehicle, obviously.)

 

No, currently installed.

 

What's the vehicle? Ford, Jeep? What year? Does it Run?

If it's a Ford, it's most likely a 6.32:1 unless it's actually a T19, then it's most likely a 4:1 but could be a rare 6.32:1 out of a large truck.

If it's a Jeep and it's the factory transmission, I believe it would be a 6.32:1 in a 76-79 and a 4:1 in a 72-75.

If the vehicle runs, it would be pretty apparent. A 6:32:1 in 1st will be almost exactly double the RPM for the same speed as 2nd gear. That's not the case for the 4:1 where the RPM would only be about 30% faster for the same speed.

 

One first needs to specify or identify if it’s Ford, Jeep, IH or other.
Then one should measure the stickout length of the maindrive.
Usually much easier to pull the shift tower and count the maindrive teeth.

 

1979 CJ5 but not the factory installed transmission. Factory 304 so factory 3 spd. PO installed the T18 and Commando/ J series Dana 20 (yeah, I don't know why the transfer case witch either).
All assembled and running (well mostly, until it breaks down on me like yesterday


I read the Novak guide...again. Apparently I'll have to crawl underneath and look for the Ford bump out on the top cover, passenger or driver's side PTO access and casting numbers.
I know it's an early version because reverse is over and up.

Your rpm vs speed process is highly encouraging. I'll try that!

 

I thought in 1976, the weird crossover year, most of the factory-equipped T18’s were still close-ratio?

Edit: I think that in 1979, the 304 was offered with the wide-ratio T18, making it one of the most sought-after CJ5 factory equipped variants. Of course, like yours, many came with the 3 speed and/or have since been converted to something else.

Like OldTime suggested, I was always told to count gear teeth to be sure... there's so many different T18 variations.

 

I crawled underneath and took pictures.

Looks to not have a bump out in top cover. I know, not a good picture. Exhaust pipe in my way.


PTO on passenger side


No adapter plate between trans & bellhousing.


But adapter between trans and D20 t/c.


Casting numbers

 

Looks like pre 1979 as indicated by case swell at upper rear.
Looks like Ford transmission as indicated by left side PTO.

 

I agree by your points and the casting digits per Novak. Interesting that no adapter was needed to bolt up to an AMC bellhousing. I'll have to check if there's an adapter btwn bellhousing and engine.
That means a 6-1 1st gear only. Woo hoo!
Thanks fellers.

 

Reverse will be toward the dash. Advance Adapters transfer case adapter. Ford case is indicated with the pto port on passenger side. With the right bellhousing no adapter needed between the transmission and bellhousing when using a Ford case and input shaft. Unless you count the teeth on the input or can count the turns you do not know whether it is a 4.02-1 or 6.32-1 first gear. Numbers on the case mean nothing as the internals could have been swapped while it was converted to Jeep transfer case. 17 teeth is 6-1 and 23 teeth is 4-1. ‘76 was a transition year and could be 4.02-1 or 6.32-1 first gear. By ‘77 they were pretty much all 6.32-1.

 

I only was referencing Novak's site. They listed all Ford T18's as the 6.32-1. The former owner has now confirmed it is a Ford transmission.
He says all he had to do was machine a .75" longer pilot bearing.

 

Most likely it is a 6.32-1 but there were 4.02-1 Ford first gear T-18’s. I’ve built a surprising number of them. You can also use a Ford pilot bushing (large diameter) and machine the outside of it down and use the outer, larger step in the crankshaft instead of the smaller inner step.

 

Then I'll have to try the rpm vs speed test.

 

I used the T-150 3 speed bell housing and bolted it up to the T-18. Had to drill out one hole to make it work, also used the T-150 front cover that the throw out bearing rides on.