Howdy
I have a quick question about my 5.3 V12 Bellhousing Compatibility. From what I have heard ,and so far understand, the AMC V8 in the cj Jeeps shares the same pattern as the TH400 that is currently in my XJ-S. However, I have no numbers or solid evidence other than pictures and a stray mention. Is this a correct assumption or am I going crazy? The Bellhousing in Question is from a CJ7 AMC V8 with the T18 Manual Transmission. Thanks for the help.
Hi-
The TH400 does not have a separate bellhousing, itâs all one unit. So it sounds like the question is âIs the bolt pattern on the back of an AMC V8 the same as a Jaguar V12?â That seems very unlikely but the truth is I donât knowâŚfrom a quick google of pictures of both it doesnât look like it to me.
FWIW the most reasonable option I have found for adapting a t5 to a jag v12 is the bell housing from https://www.5speeds.com/v12bell.html. No affiliation.
Bob
The THM 3L80 was installed in many cars. I used to take the gearbox from Rolls Royce Silver Shadows or Jaguar XJ-S V12 to the local trans shops in Fort Worth TX and the guys would say âThatâs a THM400 but what the hell is that bolt patternâ?
Then they would want to renegotiate the price of the rebuild after they found out that it was from an âexoticâ car. (Rolls does have different valves and accumulator specs.)
I have never heard of another vehicle compatibility guide for all the THM400 variances.
bob
HuhâŚ
I was hoping the th400 in the jag was the same as the ones in the jeeps. The inner Cheapskate in me is having a hard time coping with the that amount of money for just a bellhousing. I wonder if I could buy one of the old Getrag bellhousings from the early XJ-S?
You might note that, while the bolt patterns seem to vary greatly, I believe the dowel pins are always in the same spot. If you can figure out how to make use of that factâŚ
I do have access to a machine shop and welder.
Thanks for the idea, I may do a write up if I go that path.
I donât think that is the case Kirbert. The HE/T400 and the 6 litre/4L80E dowels are a match but the pre HE dowels are not.
The pre HE dowels are much more in line with the bell housing bolt radius whereas on the HE they are noticeably outside of that radius.
If you look closely at the rear face of an HE motor you can see the remaining unused bosses for the earlier dowel locations on each side
The pictured adapter is made to suit both HE and pre HE. the differing dowel positions can be seen. The small diameter for pre and the larger for HE.
.
I guess I meant that on GM400 transmissions the dowels always seem to be in the same spot. Obviously the earlier BW transmission has them located differently â although Iâm a bit surprised at that, too, as I thought I recalled they were smaller but in the same location. I guess that was wrong.
Iâm not even sure about the all GM400âs thing. There are a bunch of bolt patterns to be sure, as Pontiac used a different pattern than Chevy, and somebody recently mentioned that Rolls Royce used a different layout as well. I have no idea about Cadillac or GMC or who all else used that transmission. It still astounds me they arenât all exactly the same, with the various engine designers merely providing a universal bolt pattern on whatever block they are designing. IMHO, that certainly would have been a much better situation.
BTW, what is that adapter for?
I think that adapter is for T700 derivative from local (aussie) holden commodore to jag V12.
Iâm having a clearout, so if anyone wants to adapt aâBMW cheap Getrag to any Jag gearbox bell (6 or 12) I have the part cheap if you pm me.
Thatâs honestly something I need to research into but it may be better in the long run.
actually the 1978 onward PreHE are the same spacing as standard GM Chevy spacing to center the crank to transmission, i use a plate very close to what you show, but had to drill the Countersink holes, all the other holes lined up perfect, back 26 yrs ago bought the plate from Summit race parts!
you will also need the pilot extender part, and some countersink bolts, FAstenal in the states!
the plate was called BOP to chevy trans, (BOP Buick,Olds, Pontiac).
ron
@ronbros is the âpilot extenderâ how you make sure the input shaft still seats in the back of the crank when using an adapter plate? It basically sets the pilot bushing back 1/2" or whatever the thickness of the plate is?
@scrimbo
Only the pre-he engines had the GM spacing?
What about the HE?
I donât know much in relation to the chev angle but if you look at dowel positions the pre HE dowels align through the crank centreline while the HE are way offset from it.
Well cant say I wasnât thorough
Thanks for the info
Just FYI, In the case of our 71 eType, there were no dowels with the factory Borg Warner autobox. The holes in the block were there, but no dowels. We had to machine up a set for the 5 speed bellhousing, which in that case was a QuickTime product. We made the dowels slightly offset so that we could rotate them to adjust the bellhousing and until we got a good indication (dial indicator) that it was centered with the pressure plate.
I will be curious to see if my XJS has dowels when I pull the trans out in a couple of months.
Bob
I can only imagine that to be an oversight Bob, either at manufacture or a previous mech. Maybe.
Yes. It has dowels.
I spent a lot of time measuring them when I converted to a manual trans a few years ago.
bax , GM standardize all there GM engines in 1955 to match Chevy V8, dowels to crank centerline!
that dowel plan covers ALL GM engines from small 4 cylinder 2L, all way to 572 cu.in. 10L V8s!, hows that for making things easier for the race guys!
if Jag wanted GM transmissions , they needed to match that Chevy dowel to crank set ups!
Jag somewhere around LATE 1977 and all there V12s to the GM dowel locatings!
both PreHE, HE , not sure about the 6L blocks tho, something about drilling dowel holes ,because a place was there to drill!
the pilot spacer is available at most race shops in USA!
somwhere along the way Jag changed to (ZF gearbox,I think). not sure what happened there!
but good workable trans adapter plates are available from SUMmit racing. and some times you may have to be creative to use them!
ron