A while ago I bought a 5.3 V12 that wouldn't turn over (probably rusted due to standing still for a long time).

This engine was 100% complete, even with a gearbox.
Now I want to decode this gearbox code for fun, but after searching for a few hours, I find quite little information about it.

The gearbox code according to the type plate is: 78-ZA-8661.

As far as I know it is a 1978 TH400 (the first 2 digits are the year of manufacture).
The "ZA" should stand for the engine type, but these codes are not described anywhere on the internet that I can find.

I did find the "Z". This stood for Jaguar 1976-1988. But unfortunately not "ZA", which is on my type plate.

Also, various forums say that the last 4 digits of this type plate are the last 4 digits of the chassis number. But I am not sure about this either, because there is so little information about TH400 for Jaguars. Apparently for OldsMobile, for example, you could also see whether it had Cruise Control or not.

Does anyone know how to correctly decode this "ZA" and the last 4 digits from the type plate?

 

That website you linked is a real treasure trove.

Once upon a time, probably 25 years ago, I had a (GM published) book deciphering all the two (and three) letter ID codes used on TurboHydramatic transmissions, including Rolls, Jaguar, etc. But, something I lost isn't much good to us now, is it? :-)

The "A" is "ZA" would be the subvariant, I think. Does "A" represent the first specification? And revisions then be identified a B, C, D etc? I dunno.

Interesting research project.

Sorry I can't help.

Cheers
DD

 

From my limited understanding of GM transmissions, the last set of digits relate to the serial number of the box, not the VIN of the car. That's understandable as the boxes were made by GM and they wouldn't know exactly which Jaguar car it was going in at the time. However, I've also read that the last 5 digits of the car VIN were then separately stamped by the car manufacturer directly on the lower side of the casing close to the sump flange. That seems to be true for GM and other cars, but whether Jaguar bothered doing that, I don't know. It wouldn't surprise me if they didn't.

Cheers

Paul

 

Hi Paul,
I'll check tomorrow to see if there's a code on the sump. Thanks for the comment!

Hi Doug,
I just ordered a TH400 book (SA186) which on forums is said to explain *all* codes of the TH400 variants, I hope this also means Jaguar, Rolls, etc. If not, I'm sure this book will come in handy another time!
Do you perhaps remember what kind of book you had and whether it can still be bought?

 

Just to clarify, i think the stamped VIN is on the main body casing above the sump join.

Cheers

Paul

 

Yup, I found some pictures that showed the spot, just above the sump on the casing indeed. Thanks

 

I don't remember specifically. It was from my dealership days. I have a faint memory of it being published by "Hydramatic Division of General Motors" or something like that. The publication wasn't a retail item to be sold. It was meant for dealership use.

Sorry

Cheers
DD

 

Oh okay, then I hope it's in the book I recently ordered (still to arrive).

Unfortunately I forgot to check the number above the sump on the TH400. My X308 gearbox broke today (sometimes wouldn't go into first gear and the 3-4 shift was harsh). Of course a week before I had planned the MOT...
I'll let you know when I've found / decoded the number. Now on to an attempt at the world record fastest gearbox change

Have a nice weekend,

Terry

 

The first letter would be engine/vehicle line such as C for Chevy, B for Buick, A for Cadillac, R for Rolls, ETC.

Second letter is a calibration id. This would indicate what engine/vehicle combination it would apply to. Calibration could be the same same for a number of combinations such as a 3.8L with a/c in a Buick Estate station wagon or a 3.8L in a Skylark. Separate calibrations could be created for any engine/ vehicle group for any number of reasons. There was never a strict rule of thumb, HydraMatic only needed to know what model to build and ship to the car company. There really isn't any breakdown of what the second letter is, just a model designation. Putting a CG model valve body on a Jaguar ZA transmission could be a problem as it may have been calibrated to a 454 ci big block.

The year is correct. Be careful if overhauling because a 1988 unit in a Jaguar may actually have been built in 1987 so any updates for domestic 88 models aren't included in the foreign units. This is especially true for 88; the number of check ***** changed but the change isn't in all 88 Jags.

The 4 or 5 digit number is just a sequential number assigned at HydraMatic; it is not the vin; it may have been linked to the Vin by the car company but that was thier call. I think it was mostly just a random relationship.

Sorry for long windedness

 

its a TH400 .... don't over think it. it also has the sought after HD internals that where used in the big block Chevy motors at the time. If you want some pictures of the insides look through my build thread when I rebuilt it myself. Also there is a great book I bought on amazon (mentioned in my thread) about rebuilding one. Its pretty simple.