4 speed to 3 speed tcase

[Design311]

I've read Jim Toepper's article on swapping a 4 speed (H42) tranny onto my 3 speed tcase. Are there any other articles out there to read thru? It seems simple enough but I thought I'd ask here for any tips/tricks. Also, where is the cheapest place to get a kit to mate the two? Thanks for any advise.

 

[woody]

EASY project....$200 or so for the kits. Hardest part will be pulling the t-case off the tranny in the first place.

IMO, do a full rebuild of the t-case while in there...another $100 or so in parts.

And also IMO, this mod is ok for daily driver types, but the mere 16% reduction in low range isn't worth it for offroaders...do a granny gear instead. I kept my lower-case installed for only a few months before doing the granny swap.

 

[hammerhead]

Who has a decent price on the gear?

 

[woody]

gear only is like $100-125....pricey little bugger. SOR, MAF, TPI should all have it, just shop around. I had two of those gears at one point, sold them both. It's the 1974 transition input t-case gear....not very common.

 

[cruiser_guy]

How does one tell for sure what gear is on a certain transfer case or if a three speed case is modded for a 4 speed tranny? After all there are few stock 'Cruisers out there, many having gone through several owners and several mods some good some not so good :-\. Is there a tooth count, spline count, diameter, part number stamped somewhere or... ??? I'm assuming the gear that rides the transmission output shaft is the one that would be changed. Am I correct or is it the idler or some other gear?
I'll be looking at a transfer case to replace my blown 4 speed case in the '76 FJ55 this weekend and I'd like to be able to identify it as one that will bolt up without the requirement of a lot of extra parts.

 

[78 One owner]

IIRC the 3spd case and the 4spd case look completely different. Right?
As Woody said.. granny gear is a good option.
My brother had a three spd T case and had no advantage over my 4spd Tcase that couldn't be countered by my 20+ yrs of driving the same rig. He picked up a drastic edge in crawling once he put in an SM465 with the 6+:1 granny. However, it was not cheap or easy to do. Also, everywhere else besides crawlin, my 4sp tranny/Tcase combo runs rings around his with the big tires. Hammerhead's got 35's compared to my 33's and he won't do the 465thang, or the 3spd Tcasethang. We want Rockboxes from Advance Adapters. I have all the parts to put an SM465/NP203/4spdTcase combo together and my project completely stalled when I discovered the Rockbox. AA is gonna trade in my 203/4spdTcase adapter kit toward a new Rockbox and I might end up eating the SM465 to NP203 parts and the 203 rangebox(anybody interested give me a PM. There's a kit to mate the 203 to a 205 from Offroad Design). IMO my OEM 4spd/Rockbox/4spdTcase combo will give me awesome lowrange for crawlin, standard1.9 lowrange for sand runnin, stock 3.55 1st gear for all-around drivin with 33's or 35's without changing ring and pinion gears. Bigger than that and I'll need to change R&P ratio's, and that's waitin for ARB's instead of the Lockrights I have now.

 

[woody]

physically, from the outside, the 3-speed and 4-speed cases are 99% identical. In fact, many people will install the 3-speed gears into the less-brittle 4-speed cases, with the only mod being to properly shim the idler cluster. The nose cones swap exactly, the mounting bolt pattern is the same, the rear output cones and drums exchange, the covers are the same, etc...

Really, the only telltale sign is to either A> count the number of input rotations relative to the output in low range or B> count outer teeth on the input gear of the t-case.

a 3-speed case is 2.313 low range, a 4-speed case is 1.999 low range. 16% difference and IMO not worth the expense, but to each their own.

I do not know the tooth count, and no longer have a t-case laying around to count. You "could" count the outer teeth on your existing 4-speed t-case input gear and "assume" that if the input spline count is the same as your 4-speed gear and the outer tooth count is different that it's therefore a transition case.

 

[Gus]

I baught my 3-speed t-case to 4 speed tranny adapter from TPI (around $190), I've always had good luck with those guys, there good people. Man-a-fre has the kit for about $5-10 cheaper, but I don't like dealing with them , I had to wait two months for them to ship it before cancelling my order with them and went to TPI. It's a really easy project, just take your time and be meticulous.

 

[78 One owner]

[quote author=78 One owner link=board=1;threadid=5060;start=msg39879#msg39879 date=1063219585]
IIRC the 3spd case and the 4spd case look completely different. Right?[/quote]
Wrong! Thanks Woody! I was looking at the Tranny in the picture in my head.