A DIY rebuild of a TH400 is a very possible thing. One important thing to think about is to have the transmission coolant lines flushed out as any clutch debris gets collected there, and can mess up a new rebuild. This also means the Torque Converter needs to be replaced when rebuilding because it can’t be cleaned out w/o being cut open and rebuilt. JA4 is a common ref number w/6 lugs, but the 3 lug versions will work. A common 6 lug big block high stall converter would work fine too.
~Paul K.
I am a bit confused here…
As stated from Josep, the trans works on R, 1st and 2nd, but not on D…
When on D and stationary the gearbox is on 1st gear. What changes…?
Rear band is only difference between drive position first and manual first. Low gear one-way roller clutch is active in manual low and drive first gear; rear band also applies in manual low (but not drive)- I am GUESSING the one way clutch is NFG (if symptoms are accurately described).
Of I had a vote, which I do not, it would be repair the trans., More ATF will not restore burnt bands and.or clutched.
Aks Sprrag c;lutchj!!!
I second your vote. I’ve tried extra fluid changes, and expensive additives to try to ‘save’ a bad transmission. About all it did was buy me a week or two.
Dear all,
Thank you all for your help. I am going to look for someone to repair my gearbox.
Best regards.
Received my book today. I’m going to give it a try. Thanks for the heads up
Dear All,
Could you confirm if the TM400 ZV A is compatible to the jaguar xjs v12 5.3?
I see this on internet with warranty. I asked to rebuilt my gesrbox but in Spain is not an usually model and its difficult to find a mechanic with knowledge.
Best regards and thanks in advance.
Internally the bits are likely close enough, but that case looks different. Jaguar had their own case/bolt pattern. The pattern in your photo is hard to see, but yours doesn’t look quite right, different shaped bolt hole bosses and a missing flange. Plus that big cast “24” on top I’ve not seen before on Jaguar version of TH400.
I can’t tell you if it is identical to what you have, but the Z prefix typically identifies a 400 THM as originating in a Jaguar.
Everything I’ve found searching here and on Google says a ZVA trans is for the Jag 5.3 V12. The other tell is the 6 lug torque converter. A lot of GM applications used a 3 lug. If i was home, I’d walk out to my garage and look at the trans I took out of my manual conversion. I should be home Wednesday, if you can wait.
I see a great big 24 cast in, disproving my theories 
So the one in Josep’s post above looks correct. Note that it’s rolled a bit to its right, you’re not looking at TDC but rather the top left area of the housing.
Looks like you’ve got your answer, but you could always do a large-format printout of the flange representation I put up at GrabCad and physically compare it if you needed to:
~Paul K.
The flange on te output shaft clearly indicates t s a case for jaguar.
Teh or put shaft on the Gm application of this transmission shows only the spline to fit the slip yoke of the u joingt in to!
teh blt attern f the jag case differs from that of the case intnded for GM cars.
Carl
In the ad it says that it is from 90 to 92, however my car is from the 80’s. Could this be a problem?
Greetings.
Ok, I understand it’s like mine so I’m going to buy it and mount it on the jaguar.
thank you very much for the help, I already have mine disassembled
