T18 w/ 4:1

Ok... I have a 4:1 Jeep T18... just how impossible is it to change it to 6.32?

 

Not impossible ... the parts will be hard to find though.

The close-ratio T-18 gears are not compatible with the wide-ratio (6.32:1) gears. None of the tooth counts are the same, so they don't mesh.

The parts to change to WR exist though. The Jeep pickups and Wagoneers (FSJs), before 1980, with a 258 and a T-18, used the same input shaft length, engine adapter and bellhousing. So, if you found one of the FSJ transmissions, you could take the input shaft, cluster gear and main shaft gears and replace the gears in your transmission to get the wide ratios. However, if you can find the FSJ transmission, you may as well just replace the entire transmission. Then you'd have the WR gears and a CR transmission to sell.

If I had the CR T-18, I'd focus on upgrading the transfer case. The 2.42:1 ratio is pretty cheap, and 3.15:1 Tera Gears would give more reduction than the WR T-18 swap.

 

no doubt that the reduction is more via changing the transfer case, but it isn't cheaper than dropping in a WR t18, unless one gets very lucky with sourcing.

 

Mmm. I think it's about the same, reduction-wise. 6.32/4.02 = 3.15/2.0 = 1.57, within a percent or so.

Re the WR installation, depends on how resourceful you are, and whether you are willing to adjust the location of the drivetrain to accommodate the change in OAL. Per Nick, you can mix the Jeep T-18 and a Ford T-18, but that combo will be about an inch shorter. And I understood the question was asking if he could convert the CR T-18 to WR... replacing the CR T-18 with another transmission seems like an obvious approach.

 

you're right about the reduction under those scenarios, virtually the same.

i still think that it would be cheaper to drop in a WR t18 instead of the $700 for a 3.15 set of tera gears, even if you [not the you you, rather the proverbial you] already had the CR t18.

 

Thanks guys.... I'm actually swapping in a 4.3L V6, I have a SM465 but found the T18 with the GM adapter already there... so here's the rub: Do I use the SM465 and spend the $500 to adapt it to my Dana 20 -or- spend $800 to re-gear the transfercase -or- re-gear the T18 ???

BTW wally where would I find the 3.15:1 kit for $700?

Thanks so much for all the input

 

I would use the SM465. It has a lower second gear.

 

i have no idea. that was the approximate price 5 or 6 years ago when i looked into that option. in the end, i went in a different direction. i picked up an NP435 for cheap ($50), got a t-150 bellhousing for $30, and bought a novak adapter for the d-20 for a great price (it was less than $400 shipped). i had new driveshafts made for a total of $250. for the price of the tera-low gears, i got a slightly lower final crawl, and 4 speeds instead of 3.

wally

 

Thanks for the input guys...

I really want to keep use more Jeep parts than GM... having said that the T18 I have already has the GM bellhousing adapter and input shaft. I can get a Ford truck T18 for $75 bucks. Is it possible to just gut the Ford T18 and transplant the gears into the T18?

Am I opening up a can of worms and asking for trouble and more headache than it's worth?

 

The Ford T18 will likely bolt to your bellhousing without adapters. You can also convert the front shaft over to fit your jeep, assuming it is the wrong length to begin with. I believe the only issue is whether or not the Dana 20 will bolt cleanly....I think the T18 needs to have the "texas bolt pattern" for the Dana 20. I'm sure someone with more insight than me will fill in.

If it were me, I'd pursue the Ford T18.

For what its worth partsmike.com has the conversion parts you need.

 

You can. You use the Jeep main shaft, case and TC adapter, and everything else from the Ford. You can also use the Ford case with the Jeep mainshaft and TC adapter. Nick has covered this in earlier posts here - you'll have to search. Not sure of the details, but you'll have to modify the Chevy bellhousing to work with either the Ford or Jeep transmission case and the Ford input shaft.

 

Thanks again for the advice guys... I want you all to know what a pleasure it is to ask a question and get knowledgeable responses. Resto-moding a flatfender isn't a popular topic in other message boards, and I usually don't get unbiased replies.

The Jeep T18 that I have already has the GM trans-to-bellhouse adapter, the GM input shaft, and a GM bellhousing. Since it was a Jeep T18 the D20 will bolt right up. I was kinda wanting a run down of what I'd need to swap out the gear sets out and if it was even possible. I read Nicks post but my scenario was a little different. (i.e. would the GM input shaft I already have work?)

I hope I'm not being a pain, just would like to know what I'm getting into before I bring a 3rd transmission home... ya know?

 

You have to use the Ford input shaft, and your adapter won't work with that. The GM adapter does nothing for you if you put the Ford parts in - you'll have to bolt the Chevy bell directly to the T18 case, and modify the Chevy bell to bolt up to the T18. The Ford input shaft is too short to allow an adapter between the bellhousing and the T18.

 

So by doing what you state then that eliminates the 1" adapter... now I get what you meant by the drivetrain would be 1" shorter. So in order to get everything to spin I'd need a GM 11" flywheel and a 1995 mustang clutch kit?

Good grief Tim... what on earth do you do for a living? I see engineer, but if it ain't building Jeeps for Jeep then it's a waste of time.... you should change the Jeepin' nerd to Jeepin' genius!! Thanks again !!

 

Heh - that's Nick's job R) - I just read a lot.

 

I do not know where you are located but I have a Jeep 6:32 T-18 that I would sell. I would sell it complete with t-case and drive shafts.

 

In my case it was prety easy to find a Ford T18A, I found one on Craigslist for $50. It appears to be in good condition. I can't address switching the gears and shafts from one case to another but there were lots of the transmissions built in the 2 wd version.

 

Path of least resistance here would be to acquire a Ford T-18, '76 up CJ bellhousing, and use your output shaft and adapter. The Ford T-18 will mate up directly with the '76 up CJ bellhousing. You will need to change the pilot bushing also. To use your stock rear adapter you will need to redrill the back of the Ford case and plug the bottom left stock hole in the back of the case. This will eliminate the 1" thick adapter on the front and get you the 6.32-1 first gear.

 

The 'CJ bell will only work with the AMC engines. You need to adapt the Chevy bell to the Ford T-18 http://www.novak-adapt.com/knowledge/ford_to_gm.htm - If you are going to take the transmission apart anyway, I'm not sure whether it's easier to use the Ford case and adapt the bellhousing and the TC adapter, or to use the Jeep case and only adapt the bellhousing. I understand that the engine end of the Jeep case is different from the Ford case by one bolt location, and that is easy to deal with.

 

Ooooops. Forgot he was going to a GM engine. Easy enough to modify the Ford case or modify the bellhousing or a combination of both. The Ford front bearing retainer will need to be machined though.