Budget Trans Options For A Gm Bell Housing?

It was 75 deg hear today in east TN, got me to thinking bout spring? When all winter chores,
Firewood and trips to store in snow, are done I'm going to start my 3.7 boat engine install.
Before I lay down $$$ for t90 adapters, I was thinking what other options I might have?
I might could find a 3 or 4 speed tranny that would bolt go my GM bell without an adapter?
I've read novac and advance web sites, BUT I'm still confused as he%&.
What other trans are useable, relatively easy go find and don't cost an arm and a leg, that will
allow me to use the Dana 18?
All comments, and recommendations welcome!
I know 0 about these conversions?
It would be great to install a tranny that cost less, or same as the adapter.
I want to keep the off center diffs and Dana 18.I did notice the 18 was adaptable to several
different tranny! Let's hear some,(What would you do commets).
Remember the new engine makes bout 200HP, and 300TQ.
I'm not hard on equipment, but would like it reliable ,and bulletproof to all but a teenager? LOL
PS I have some connections with a 60s,70s, chevy classic truck restore shop, that junks several straight shifts, in favor of autos, he says they sell better witbout a clutch!

 

Adapt up front or to the D18. The transmissions can come cheap, but the adapters don't.

 

I would rather adapt the 18 than the tranny, especially if I could find a 4-speed , with or without. Bulldog 1st?
Unless the 18 adapter causes more headacks than the t90 adapter?
I realize I may have to change driveshaft length!
Hope to do it once and forget about it?
I Also have a son tha t works at a factory with some cnc metal working equipment!
If adapter relatively simple we might make our own?

 

Adapting the GM Muncie SM465 to the Jeep Dana Models 18 & 20 Transfer Cases
Adapting the GM Muncie SM420 to the Jeep Dana Models 18 & 20 Transfer Cases
Adapting the Borg Warner T18 & T19 Transmissions to the Dana Spicer Models 18 & 20 Transfer Cases

 

If budget is your main concern, the t90 adapter is much cheaper than a trans to tcase adapter, and you could probably find one used for dirt cheap. The t90 should be fine behind the boat engine, if you don't hammer it too hard.

 

465,420, 18,19,what trucks might I find these in?

 

Thanks for links, looks like using what I have, even with a re build, might be best way to go?

 

SM465 would be the easiest to find. I got mine for a case of beer.
You can find these in Chevy full size 3/4 + ton trucks.

 

Personally, I'd do anything in my power to not use a t-90 behind that boat engine. Scour craigslist, FB marketplace, the WTB classifieds here, talk to local 4x4 club members... somewhere out there you'll find a complete setup, or the parts you need to piece something together for the same cost of several rebuilds of the t-90 after it explodes a few times. It will need to be babied behind the torque you'll subject it to if you want it to survive. I don't know about you, but I don't like to do things twice.

 

ECJ5

 

Saginaw car trans with adapter: ECJ5

 

Depends on how one drives and how big the tires are. At least with tires up to 31's, a T90 can survive behind a little power. I ran my stock T90 in my 3B for 2 years mated to a rather healthy 327 sbc with nary a problem. I was using the H78-15 tires that came new on my CJ 5.

 

Personally if you have the ability to scrounge for parts and have someone that can do a little machining(input bearing retainer) for you. The cheapest route is to find a 2wd ford T18 or T19 and a T18/Dana 20 setup from a J-truck or a International. You can use the trany/T-case adapt for your Dana 18 and the Ford trany should work with your standard depth GM bell with a little drilling. Now there is a little more bit to this but nothing to serious.

 

This is what I did. I'd be happy to help if I can.

 

Not to stir the pot or anything. I can share my experience with a couple trans. options.The Saginaw or muncie 4 speeds are strong and a bolt-in to your GM bell .The main draw back is shifter location and lack of low 1st gear ratio. To get the full potential from your engine I would look for a rugged 4 speed. Probably with a granny 1st gear

 

I've been running a T90 behind a 225 for 19 years. Is it perfect? Certainly not. I'd love to have a T18 or SM465. But it was what I had when I built my Jeep and it's served me well for many summers of 4 wheeling.

 

-My favorite is the Sm420. It has 7:1 first gear, the lowest of all the Truck 4 speeds. The SM465 is great too...albeit BIG. The 465 and 420 have the same GM bolt pattern but the 465 has a larger input shaft bearing retainer. And so, depending on the bell housing you have, the hole may or may not need to be machined to fit the 465. Both gear boxes can be had cheap...the t-case adapter, not so much.

Just a few points:
-SM420 is available from pre-68(?) Chevy/GMC Trucks, and the SM465 from anything later than that.

-They both have their quirks for an install, including a fair bit of floor work to fit the shift tower. A 1" body lift can help out with this.

-The bulge on the SM420 box will likely need some grinding on the passenger side to clear the front shaft yoke at the 18 T-case.

-SM465 is BIG. A Good center of gravity creator. Massive shift tower. 6.5:1 first gear. Novak makes a 1" adaptor for the 18 t-case.

After drive shafts, etc, etc....its generally not a "cheap" conversion. Worth it? Definitely.

 

Plate adapter and short t-90 is my vote to get it running.

 

He said he didn't want to do it twice

 

Does it count if you don't pull trans out?
If I recall his engine is loooong for a 4 banger. So this might keep him from getting too short on the rear driveshaft.