Hello Friends,

I have to decided to take on the task of rebuilding my TH400 after being quoted $3200 for a complete overhaul by aamco Transmission shop. Originally the car was stalling through all gears. I had replace the filter and things were good for about 2 weeks then it developed a HUGE LEAK. I would park the car at school and comeback to a pool of tranny fluid underneath. It got so bad that everytime i parked the car and came back there was cat liter thrown underneath lmao.

When it comes to automatic transmissions I am not the brightest but many seen many rebuild videos with people suggesting it isnt difficult. But so far from my research I decided to get this deluxe rebuild kit from rockauto https://www.rockauto.com/en/moreinfo...78816&jsn=2186 , a highstall torque converter. If you have any good torque converter recommendations let me know. I also keep hearing of a torrington bearing upgrade in videos and forums, but I need more information on this. Could someone educate me more on this? also any good techniques for dropping the trans? If you have any experience with prior rebuilds please shine your wisdom on me

 

I have not done a TH400, but I have done a Ford C6. First, I would say get yourself a good manual, read and understand it completely before you start. Second, follow the specifications and clearances exactly. If there is supposed to be a particular clearance in a clutch pack, make sure it is within specification. If it isn't, it means something is wrong and it will bite you later if you ignore it. Third, take your time, patience is a virtue here. And make sure everything is scrupulously clean. Bits of lint, threads from rags etc will ruin your day.

You can make a transmission stronger by increasing the number of frictions and steels, you can often add one or two, with a corresponding thinner backing plate. The wave steels (not sure of the exact name) that have scallops around the edge are a weak point in the TH400, they typically fail around 100,000 miles. Make sure those are all new, don't reuse the old ones.

The starter will need to come off, and that is difficult, you'll need a 12 point socket for that. Consider having it rebuilt, or put in the latest gear reducing type starter. Most V12's had those from the factory, I'm not sure when they were first introduced.

It's a very heavy transmission, make sure you have a good transmission jack and do the removal on a hard surface, like a concrete floor so you can roll the jack around easily.

I don't think I would go away from the factory torque converter spec without a good reason. It's a lot of work to take it out again if you're not happy with an aftermarket one. All depends on what you are trying to achieve.

 

I cannot help on the rebuild, but this might help you get the box out of the car!
https://www.jaguarforums.com/forum/x...ox-xjs-221677/

I am not saying it is the best way, or the only way, but it worked for me! If you look at post number 19, point (d) in the thread, you will see it says:
"Undo the 9 of the 10 bellhousing bolts, note these 9 bolts have 9/16ths inch hex heads. The tenth bolt is the one fastening the topside of the starter motor; this bolt is NOT a normal hex headed bolt, it has 12 points on the bolt head and you MUST use a 7/16ths inch 12 point (ie double hex) socket to undo it. "
This is the bolt that jagboi was referring to.

 

I think it's 7/16", not 7/8" I know it certainly isn't as big as 7/8"

 

It is indeed 7/16th, my mistake in the original. Thanks for pointing it out. I have amended my post above, and the Chief Moderator has kindly agreed to correct the original thread..

 

Not a TH400 expert by any means but just asking if you could pin-point where the leak is coming from. I know you want to get right in there and do the overhaul, but from what I've heard, the TH400 is pretty robust mechanically. Perhaps an oil cooler line is leaking at the fitting or at the flex hose, or the vacuum modulator, or front seal, pan etc. At least for me, I would want know exactly where the leak is and go from there..unless you have already made up your mind about the rebuild.

 

Wasn't sure if this could help or not...

https://vancouver.craigslist.org/rds...064256268.html

 

here s a link to mine i did a few years back, you will need a few specialist tools, but it will be much more rewarding than sending it out and paying out lots of money

https://jec.org.uk/forums/viewtopic....&hilit=gearbox

BB

 

Hello

Daim also did a good write up and posted it on the forum for us

https://www.jaguarforums.com/forum/x...ebuild-194241/

Cheers
Steve

 

If only it wasnt a few thousand miles away

 

I have one thats rebuilt and never installed and I will sell it cheap. It also has a fresh 6 lug converter. I live in Virginia. My number is 540 347 5185 thanks John

 

I am not sure, I don't think it was coming from the pan gasket, i suspect one of the seals closer to the driveshaft. I have already made up my mind to rebuild/ overhaul it just because of the fact that the trans was smoking too and from the trans shop, and heat is a killer to trans.

 

Considering this is 20mins from me this helps me lol, I want a spare to upgrade. not sure about the original poster. I have another transmission off a V12 but he is quite far away...

 

Smoking was probably due to the fluid leak dripping on the exhaust...but ok, I see are determined to the do the rebuild. I'm curious to see how it will behave with new parts, seals etc., after the rebuild. Good luck.

 

Is the number you listed correct? i reached out and nothing

 

At $3,200.00 rebuild cost, I'd be :
1) looking elsewhere, mine cost $1,200.00 WITH A SHIFT KIT, ALL IN ( MY MECHANIC BILLED OUT AT $100.00 / HR )
2) LOOK AT A UPGRADE TO THE GM T700 4 speed kIT FROM WWW.JOHNSCARS.COM. THE TRANNYS THEMSELVES ARE DIRT CHEAP
3) SPEND A EXTRA $4k, ALL IN , AND BE VERY / EXTREMELY PLEASED WITH A MANUAL 5 SP

JUST MY THOUGHTS

 

Hey! Awesome... Did it work out?

 

I second the idea of considering looking at putting the money into, 1, A 5 speed setup (still going to be expensive) or 2, Johns Cars 700R4 setup (you'll need a toughly built 700R4 though). That's a wack price from Ammco. The Th400 is one of the easiest and cheapest transmissions to rebuild, so much so that it's worth learning about it, worth learning what trans supply shops are in your area, and ensuring you put in updated parts IF you go through a rebuild.

I relied on this book by Ron Sessions when I did mine, along with the standard $20 ATSG GM guides, as well as the paperwork from the various components I sourced individually. By now there have to be a bunch of good youtube videos on this.





In addition to upgraded sprags etc recommended in the book above (and I'm sure there are now other good books as the one above is quite expensive) these days, I specifically bought:

A TCI kevlar reverse band
A B&M Shift Kit for the valve body
A Derale pan with cooling tubes in the bottom
RedLine ATF.
Extra clutches (re-arranged the steels & thicknesses to provide for some extra friction)

Get to know your local transmission supply places - or those in the nearest big city.

You'll need a transmission jack - at least to get it back in. Yes when I was much younger I took it OUT bench-press style.. (never again). The toughest part is the top two bolts which need a strategically placed swivel and some LONG extensions - preferably one with a wobble end.

Zip lock bags permanent marker and cards help. There's a bit which holds a a ring of springs in tension in the direct drum, and it's quite tricky/difficult to re-assemble without the proper tool to put it in compression while locking it in place.

I had broken the front input shaft hub clutch assembly (I've long forgotten the proper name for it). Essentially the big front drum/hub that contains clutches had spilled them out after snapping off some of the teeth that held in the snap ring retainer. I had to replace that. They do make it in steel, but it's very expensive. The only thing I did kind of wrong was mis-estimate the spring (which tension) I need to use in the reverse band servo piston which results in a slam into reverse. It's not bad and I've never bothered to go back, dive in and fix it.

~Paul K.

DO NOT try this without a reasonable air compressor and a place to get things CLEAN CLEAN CLEAN though.