The TH400 is probably one of the most reliable transmissions ever made. As the successor, the 4L80E is also from 1st to 3rd gear also just a 3L80 (aka TH400) it is just as reliable. I mean, even Rolls Royce used them... And they were fitted from 1964 to 1998 by GM, some even til 2003. Mostly innheavy duty application.

They suffer from hard shifts from D to R or R to D. There are shift improver kits available. Depending on age and transmission fluid service status, I'd consider a rebuild. I'm doing one right now. Don't expect it to be cheap. And ypu won't really find a overhauled one, as the bolt pattern of the torque convertor housing is totally different to that of a GM V8.

 

In general it is one of the most tough and reliable autoboxes ever made. If yours has done 90,000 miles it would be worth a refurb; but if (say) 50/60,000 and you intend to do only a few thou a year at legal speeds, not really needed. A refurb by a decent place should come in at 1,000 - 1,200 UKP, especially if the box is out of the car and delivered by you to them. I know a really good guy in Luton, but I am sure there are places nearer to you.

 

 

 

When the fluid smells burnt then there is a burnt friction disk and fluid change won't fix it. Tip for used car buyers - sniff the fluid.

 

 

The 400 is a tough old bird in terms of being able to cope with heavy loads and lots of torque ....but exceptionally long life is not a sure thing. Not unusual for a 400 to need an overhaul at 80-100k miles...though many go much longer, it's true. For almost all applications they were calibrated for smooth shifting....which increases wear on the clutch plates.

The best time to overhaul any automatic transmission is before it actually needs an overhaul. And certainly before actual failure occurs.

If done preemptively....or at the very first signs of getting weak....you can often get by nicely with a 'soft parts overhaul'. Clutch plates, seals, gaskets, new modulator on GP. Small stuff. If you wait till the box is slipping badly or has failed, you're likely into a "hard parts overhaul" where you need clutch drums, planetary gears, etc. Things start getting expensive.

Cheers
DD

 

I'm still in the process of getting all parts together. I'm already at around €450 for besrings, clutches and co. Still need more parts... Just as a price reference.

 

the old GM 400 box was engineered back in 1962,released for sale in 1963, not bad for American engineering!

used by many GM cars along with Jaguar ,RR and some trucks , modified by some to handle 2500 lbs.ft. torque !

now we have its grand son 4L80/90E,,, ihave a Diesel suburban(ugh) with close to 200K on it, and trans is perfect, cant say that for the engine tho.

ron

 

And GM never saw fit, after all those years, to fix the notoriously noisy first gear !

Cheers
DD

 

Tis in the genes!!!

Our first post WWII family car was a 50 Pontiac fast back. Straight eight and three on the tree. Talk about first gear noise....


But, dad and mom kept it til he gave up driving. Passed it on my brother. He drove it for some more. then swapped it in for a pickup. used for used ??

Carl. l

Carl

 

It seems typical in Jaguar V12 service that the TH400 doesn't last much longer than 100,000 miles. The steel disks in the clutch pack typically break up at the scallops around the edge. When mine went then first and third gear were engaged at the same time, and that quickly burnt the fluid.

 

I've yet to tear down my car's original TH400, but that transmission has 78.000 miles on it. The one I am overhauling has about 130.000 miles... I was told the car still drove with the snapped pressure plate, but on the other side: I can't say anything. Which is why I am striping it down. I'll probably use all the mechanicals of my proper transmission in the case of the old worn transmission. I doubt I'll be puitting 5.000 miles on her a year but hey, enough for a yearly service.

 

 

.

my suburban 4L80 has no noise from any gear,, 200K and holding! i actually tow with some times.
almost forgot, my Buick GN with LS2 and 4L80E , perfect all around street car, suspesion mods made it handle lightyears better, also 2002 Camaro brakes!
ron

 

Too bad you are not local to me in Texas USA. I have a NEW-IN-BOX THM400 (3L80) that I would sell for the price of a rebuilt unit.
It is still in the wood ship crate with steel bands. I think it was made in the early 1990s for all 5.3 XJ-S from 1989 onward.
Part number EBC3654N. I would guess shipping to Europe would end up costing more than you could get a reman locally.

I have a 1988 C2500 Chevy Pick-Up that has a THM400 and thought about stripping the Jaguar internals and putting them in the Chevy case but the truck is working fine so no point I guess. It would be a waste of a good Jaguar gearbox to fix a common Chevy truck.

bob

 

 

Look into a freight forwarder/consolidator. If you can pick it up at the airport and do the customs clearance yourself ( which isn't difficult) airfreight can be surprisingly inexpensive. Door to door adds quite a bit to cost compared to terminal to terminal.

 

The TH400 is a good half pallet item. They aren't super heavy but are a little on the heavy side to Lug around...