Greg I hope I did not cause offense about my comment on shipping! I greatly value your input! I'll be using your ground 15MM socket trick for unbolting the torque converter after I finish lunch/this post.

I did go into this obviously very naive - hey "rebuild it all" looks relatively economical and for sure fun way to fix the shakes the car had and I can call it job done for years. It is sounding like a better plan is only replace specifically what is needed with best I can get quality.
Probably a dumb question - but I'm about as far as you can get from being a mechanic by trade, I'm just a guy who likes learning how to work in stuff.
How do I know what I can leave?
There are parts with obvious deterioration (sway bar mounting and link bushings especially), steering rack gaiters. but just looking around the suspension a whole lot looks "normal". And in the case of the ball joints (they are rebuildable type) the gaiters have some deterioration but I not feeling/seeing any sort of play following typical inspection procedures I've read here.

Again thank you all for the knowledge!

 

Oh wait a minute! I have the engine out … there is a plastic plate on left side that appears to cover access to flex plate bolts!

 

Greg I hope I did not cause offense about my comment on shipping! I greatly value your input! I'll be using your ground 15MM socket trick for unbolting the torque converter after I finish lunch/this post.
Not a bit!

I did go into this obviously very naive - hey "rebuild it all" looks relatively economical and for sure fun way to fix the shakes the car had and I can call it job done for years. It is sounding like a better plan is only replace specifically what is needed with best I can get quality.
Agreed

Probably a dumb question - but I'm about as far as you can get from being a mechanic by trade, I'm just a guy who likes learning how to work in stuff. Me too

How do I know what I can leave?
I suggest that you post closeup photos of; Lower wishbone inner fulcrums, Rear radius arm bushes, Rear cage mounts, Front subframe mounts and let the guys give you their opinions.

The last thing I meant to do was suggest something that would not be fun, so as Doug said, above, look at everything and decide on a necessary to replace or not basis, seems a good plan all round. Good luck.

 

Like I say toooo many times,

Ya gotta keep the beer fridge FULL, and your fluids UP, or you miss all the fun stuff. like that hidden hole.

 

Hey Thom I’m in Jaffrey NH, where are you? I’ve rebuilt three th400 XJS transmissions and only one failed! The one that failed was because I mixed and matched parts out of two transmissions. If you’re rebuilding a transmission and use all the same hard parts and shims, the clearances are perfect.

 

I'm in Hampton - and I'm decided to give rebuilding a go myself - I've got a nice study well lit table in the basement close to the beer fridge!

So... thoughts on suppliers for the rebuild kit?

 

Many companies put together kits, just look for one with Alto Red Eagle friction, Kolene steel, and two new bands. I think I used this one:

Compatible With: Chevy GM TH400 Alto Red Eagle and Kolene steel Deluxe Transmission Rebuild Kit level 2 https://a.co/d/4DJCvYb

There are much cheaper options.

You also need an aluminum accumulator piston.

Replacing the bearings requires special tools. If you want to drive out to Jaffrey and use my press and tools here, you’re welcome to.

The book to follow is: HT Rebuild & Mod GM Turbo 400 Trans (Workbench How to Series) https://a.co/d/69g8mcT

 

I've built hundreds of TH400's over the years in the business and using good quality clutches is a must. Most of what you find online are intended for the hot rod group and the quality can be lacking. i only use Borg Warner friction materials in builds intended for the street and a good quality rebuild kit. Check the bushings for wear, especially the center support, output shaft and case bushings. An arbor press comes in handy for replacing bushings. As your car won't go forward, the most likely cause is the forward clutch failed. A worn governor can lead to a forward clutch failure, check the diameter especially near the drive gear, should be .800".

 

Well got transmission mostly disassembled. I guess it has been gone though before - has Transtec branded gaskets. I didn’t find anything damaged other than those fragile orings. Was a grey sludge covering in areas. Now just waiting for the rebuild kit.

 

I'd replace the steels while you are in there, they seem to fail at about 100,000 miles.

 

The plastic sealing ring that's in two pieces I assume is the front one. The usual cause of this failure is too much end play and the seal does not stay fully contained in the drum and blows out. The aftermarket makes a thicker washer (Sonnax 34301-.094) for the clutch hub that moves the drum forward to prevent this. If you end up with not enough end play after installing the thicker washer, the fiber washer on the back of the pump is selective and you can install a thinner washer here to compensate. Setting the end play on a TH400 is a two step affair, you must set the rear unit (geartrain) end play first, then check the front unit (clutch drums) end play with the geartrain held forward.
The sealing rings you get in a rebuild kit may be cast iron rather than plastic, I prefer the cast iron ones for a stock rebuild.

 

Well... the rebuilt took a turn for the different. For sure this transmission was rebuilt in the past. Yes that is the forward seal. And...the forward drum piston I don't know -The first steel was dished which I read here was expected. The piston was stamped steel and it did not have the "wavey ring that the first steel would sit on that I've seen all over the internets- there was just a ring spot welded flat ring and that did have a broken weld so it would move and me being admittedly clumsy/stupid broke that ring it all the way off. Piston needed to be replaced.. I also saw I guess evidence that to my untrained eye suggested that piston moving oddly - hard black residue from a seal on one side of the drum like it had rubbed oddly. I found a few other things like governor gear had some wear, my speedo sender I am pretty sure wasn't working... so cost was adding up and my confidence was not...So long story short I found XJS transmission with speedo sender - yeah I'm out the cost of the rebuild kit, steels etc. (tools don't count) and yeah I could have problems with the replacement transmission- but I'll replace the filter anyway so can roughly see what's up and I guess hope for the best. I vac sealed all the parts and I'll rebuilt it at my leisure. Now back to the suspension for which I am starting a new thread.