F head to t18? Need deeper gears.

Maybe I should make two threads for my current debacle. But for now I'll start it as one.

Currently I'm running an early cj with a dj body, F head, t90A, stock axles with 5.38's, and 33" tires. I've been wheeling with it a couple times now and it just doesn't crawl along the trails well.

So I've been looking for a new trans to put behind the F head, because I really like having a small motor in my jeep. A guy I know has an AMC t18 with a d20 that came out of a cj of some sort, so it has the short adapter. I'm planning on going to wider axles so the d20 rear output is good to go. Ideally I'd love to put this setup behind my f head. Anyone been able to do this?

My other option is to put the 360 thats in my garage in front of the t18/d20. I was going to put that motor in this past winter but decided against it because of the extra work I didn't feel like doing.

Thoughts, opinions?

everyone likes pictures!




its a little narrow for the tippy spots


and these bodies are really tall. That is a 5.5" lifted xj on 35's

 

From '71 through '76 the CJs came with a close ratio T-18. This transmission does not have the deep gears that you are looking for. The T-18 with a granny gear was only used in the CJ '77-79. Plus the Dana 20 will give you a worse low range ratio - the Dana 18 low range is 2.46 while the 20 is 2.03, or thereabouts. With a CR setup, you'd be back where you started with the T-90 and D18.

There is a T-98 transmission that was offered with the F134. It's the predecessor to the T-18, and it has the low gears that you want. But they are scarce and expensive (typically) on the used market.

If you are willing to swap engines, there are many different combinations that can be made to work. Search old posts and you'll find lots of discussion.

 

An F head with a 6:32:1 first ( Wide Range T-18 ) , 5:38s in the axles, and a 2.0:1 low range (Dana 18 ), will give you 4.86 mph, or a crawl ratio of 64.56 at 3,200 RPM (Red line for a F head.)

Sounds like a lot of work for a poor little F head? :?

Like Tim said, that transmission would probably be the close range T-18, with a 4.02 first.
So, that would actually give you a ratio of 43.25.

 

The Dana 18 had the 2.46-1 low range. Dana 20 had the 2.03-1 low range.

Hermtheoverdriveguy was working on a kit to convert the T-18 to fit F and L-head engines. Not sure if it's available yet but worth contacting him.


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Shoot! I knew I missed something! Thanks Nick, that would be the Dana 20 that I used that math.

 

This t18 has the 6.32 first gear apparently. I'll get a hold of herm, otherwise I think I'm going to plan on putting my 360 in front of the t18. I would love to keep weight down with the f head though.

 

Huh, just found a 4.3 GM for $75… The t18 adapter for that is $220 from Novak. Might have to look into that a little.

 

Novak or AA makes an adapter to put a np435 behind the F head. The thing is you need an adapter for the Dana 18 to the tranny. I couldn't figger out why a person would spend 1k in adapters just to have an under powered Jeep. I've been planning to use a 4.3, SM-465, D18 in my M38a1. Nice low ratios, plenty of steam for the hard road, and an overdrive will bolt up nicely.
If you're dead set on a t18, use an engine that will bolt up to it. Less money spent on adapters and custom parts the better.

 

I totally agree. I have a real hard time spending money on stuff like adapters when they shouldn't be needed or used so much. I'm picking up a running '93 Blazer that will be giving it's life for my postal jeep. I'll be mating the t18/d20 to that with either a cheapish adapter (yeah hypocrite I know), $220, or drilling out the bellhousing like I've heard about. Have yet to find any information on it though.

 

If you find a T18 out of a Jtruck that has the I6, I think it can be made to work. I have a buddy that has a 4cyl T98 and I did some comparing between that and the T18 I have out of the said Jtruck. The factory adaptor is the same as T98 4cyl one. Only thing is, the input shaft lengths are less than 1" difference. It was hard to get a good measurement of the input shaft of the T18, because it is in my jeep. It is, however, the same as a T14 used in V6 CJs. Might want to look into this possibility.

 

Be careful of how you plan to mix and match input shaft lengths. The shortest input shaft is used with the Ford T-18, and it is the right length to work with a Chevy bellhousing. Novak has a page about this - http://www.novak-adapt.com/knowledge/ford_to_gm.htm

The Novak adapter is specific to the stickout length of the CJ T-18 in question, not the gear ratio. They don't explain this very well. The close ratio T-18 was introduced in 1971, and uses an iron plate adapter and the T-14/T-15 bell, for a stickout of about 7". I believe this setup was used through 1975. In 1976, a new bellhousing was used, and it continued through 1979. But the 1976 transmission is close ratio. The wide ratio transmissions for the CJ were used '77-79. Contrary to the Novak site, there was no T-18 in a CJ in 1980. I don't know what the stickout of the '76-79 transmissions is, but it is a different part from the earlier transmissions, so I'd expect it to have a different length from both the Ford and earlier Jeep T-18s. From the picture of the adapter on the Novak page, it looks like the length will be between the Ford and earlier Jeep shaft lengths.

If there's a tag on the transmission in question, post up the PN. It should be 5358092 or similar.

 

Thanks a lot for the heads up. I'll look into it. From what I hear if I use a gm manual bell housing (I don't remember if there was a specific year range), use the 10.8" I think it was fly wheel from the Camaro, the '77-'79 t18 will basically bolt up to that. What needs to be done is drilling/tapping of a couple ears on the bell housing.

Side note, timgr, I also have a golf sport! Mine is Surf Green.

 

Pretty sure that only works with the Ford input shaft. You can install the Ford input shaft in a Jeep transmission, then you'll have the right stickout for the GM bell. The Jeep case is only one bolt different from the Ford pattern, so the bell can be drilled similarly to the Ford-to-GM instructions linked above. However, the kit from Parts Mike (Ford input shaft, retainer) is ca $200, so you may as well go with the Novak kit and use your existing shaft with no redrilling. Call Novak and ask them.

What year is your Golf? Mine is black - only three colors were offered that year for this model: red, black and white. There was no 4-cyl GTI in '95, but this car is its equivalent. I heart my Golf ... too bad it's showing its age and the New England road salt.

 

I'll have to look into the shaft lengths. My other option is going to an sm420 or 465, but I don't know what I'd do for a tcase. I suppose I could go with a drivers drop front axle and open up tcase options. I like the twin stick option with the d20 though, obviously its not going to work with a drivers drop axle or the sm's without $$$. Is it worth more than the ease of using maybe a cherokee axle…not sure. Whats a good drivers drop tcase option? I really like the idea of cherokee front ends, being as they are so easily available.

I got my 4.3l vortec today. Started pulling it out too. I put the f head for sale yesterday and it sold this morning. Apparently $250 was a cheap price to pay for a very well running f head.


Also Surf Green was only offered in the golf sport's, and mine is a 95. Its a goofy color, but I absolutely love it. My car is a rusty beater with some euro parts on it.

 

Cherokee axles are much wider, wrong bolt pattern, coil sprung, use unit bearings (no locking hubs), and many have axle disconnects.
If you're gonna go driver's drop and wider I'd suggest a Dana 44 from an '80 or newer Wagoneer and swap to Ford hub and rotors for 5 lug.


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Oh I forgot to mention I'm likely going to use a ford 8.8 rear end, which is a 5x4.5 bolt pattern like the cherokees. And yeah I'm looking to go wider. What would be a good choice of tcase to use for that axle though? Something short obviously.