some h55f and split case tech (1 Viewer)

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orangefj45

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there have been sooooo many threads on here about which split case to use on the back of an h55f and there's a lot of mis-information and lack of info out there.

so let's try to clear this mess up a little.

first off, i highly recommend to my friends and customers that they buy a new transmission from the toyota dealer. if you do some shopping around, you can usually find them for $2500 or less.
sure, you can buy a used trans that came from OZ or wherever but there's a reason why it's for sale and no longer in the vehicle it came out of. down under cruisers are what 70-era domestic pickups are here. workhorses. they don't live a pampered life, they get used. every day. day in and day out.
so by the time the transmission comes out of one of these donor trucks, it's seen a lot of rough miles. i have rebuilt a few of them and they're usually just about worn out. by the time you buy a used trans for $1000-1200, then buy a rebuild kit, synchros, possibly a new input gear and pay for the labor to have it built, you're already at or above the cost of a new unit. and you're still the proud owner of a gear set that's most likely going to make some noise since it's got 200-400k miles on it.
simply put, buy a new one!

second, there's a common mis-conception that only the 38mm idler style split case will work on the back of an h55f. not true! any split case produced after 10/82, no matter if its' got the 34 or 38 mm idler shaft, has the provision for the 5th gear oiler and can be used on an h55f transmission. i've built a few.....

however, there are some differences when it come to h55f transmissions:
1) there are at least three different input gears.
2) there are at least three different top covers.
3) there are at least two different main shafts.

since this post is geared towards transmission to t-case tech, i'll leave #1 and 2 alone for now and will focus on #3.

main shafts differences! from what i've seen, the h55f transmissions offered with manual shift t-cases are slightly different from the vacuum shifted cases. the splines on the rear of the main shaft, where the t-case inut gear rides, feature the same tooth count and tooth pitch, but on the manual shift case the splines run all the way underneath the bearing just in front of the front split case half. on the vacuum shift cases, the spolines end about 1/4" shy of the bearing and the useable portion of the splines ends about 1/2" from the back of the bearing surface.
this affects how much spline engagement area the shaft offers for the input gear since the gear butts up to that bearing.
what it comes down to is that the vacuum shifted cases utilized shorter female splines in the input gear. the reason for that is that the splines on the main shaft are "shorter".
in other words, you can not run a gear ( and entire split case ) on just any h55f. the h55f originally sold in conjunction with a mechanically shifter t-case will accept anyt split case from 10/82 and up. so you can use the later style 34mm case, the mechanically shifted 38mm case or the 38mm vacuum shifted case with the bearing supported output gears. from what i've seen, all the vacuum shifted cases also feature the bearing supported output gears. i'm not 100% sure if this is a fact or just that i have'nt seen any different. please correct me if i'm worng.
this also means that if you have an h55f that came originally with a vacuum shifted t-case, then you have to run not only a 38mm case, but you need to run the gear set out of a vacuum shifted case. these have the shorter female splines in the input gears and can potentially wear out faster since there's not as much contact area.........
the one exception to all of this is the fact that we do have the luxury of being able to purchase a McNamara gear which has the offset splines and will worn on either trans.
a couple of pics to follow. hope this helps!

georg @ valley hybrids

More tech: just added another thread about building a late model 70-series new OEM split case onto a “short” 19-spline H42 transmission:

 
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"short" main shaft splines.
image-2935398120.jpg
 
Completed combo with vacuum shift case converted to mechanical linkage. I rebuilt this particular h55f since it came with a 1HZ engine we're transplanting into an FJ60.
image-3646982298.jpg
 
And this is another h55f combo I built this last week as well. New trans from the dealer with a 34mm case. Going into a 40.
image-3596366880.jpg
 
i don't have a great pic of the "long" spline h55f main shaft right now, but i have another trans coming in less than two weeks for a sweet fj45 project, i'll take some pics then unless somebody has one handy.
 
and one more tidbit about the h55fs. even when i buy a new trans from the dealer, i remove the 5th gear extension housing and apply some loctite "formula 518" to the gasket. i've seen a few of these transmissions leak between the main case and extension housing and i've heard a few people complain about it. doing this only takes 20-30 minutes ( if you get interrupted by customer phone calls :lol: ) and it's well worth the effort! you have to remove the 5th gear detent screw, spring and check ball but none of the linkage or levers. pretty simple really.

here's a crummy pic. sorry, all of these were taken with an iphone.....

hth

georg @ valley hybrids
 
Fantastic write up and pics Georg
 
thanks guys. i built 3 split cases last week. helps having an apprentice to do some of the clean-up and prep work. :cool:
but i'm way too anal to let anybody else in the shop even attempt to build any transmission or t-case that comes thru here. :eek:


georg
 
probably should be a sticky or in FAQ

nice job georg.
 
T-case strength?

Georg,

Good thread, I appreciate the info. I'm at the point where I'm about to choose my t-case, I've got an H55F going into my 40.

Of the essentially three variations on the split t-case, is the later vacuum shift case with its anti-friction bearing supported output shaft that much stronger? Is it worth the penalty in reduced ratio (I believe it's 1.9 as opposed to the earlier case's 2.6ish ratio)

Is the 38mm idler t-case much stronger than the earlier 34mm idler t-case?

I'm going to run a 2UZ V8 in front of my drive train, but I don't know that the strength of any of these cases is a factor really, I haven't heard or read of anyone blowing up a split t-case of any description, even with a V8 in front of it.

(This is probably the point where everyone who has had a t-case fail comes out of the woodwork :))

On another note, I manage to wrangle an OEM drum park brake conversion kit, does the later vacuum shift case have a different diameter output shaft when compared to the earlier variety? Makes me wonder if the output shaft that I have in my kit would work with a vacuum shift case... :hmm:
 
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Great write-up. I will contact you when I pull a 13BT with Trans/vacuum transfer from an old BJ74 to put into my FJ40. I will want to switch the vacuum to mechanical at that time.
 
Anybody wanna see a pic of my long shaft? :eek:


Great info, Georg !

FAQ-FAQ-FAQ!!!
 

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