Anyone know anything about TH400 boxes or Chevy 6.2 diesels?

Gratuitous photos...






As an aside, the diesel pump is a thing of beauty, if difficult to see down in the valley. With the pipes on it looks like one of the squid-thingies out of the matrix!

I had a Chevy blazer with that engine (and I think same gearbox) or was it a 700r4 or somet ?

That had a T.V. Cable between throttle linkage on pump and gearbox.
Adjustment of that affects kickdown and shift points.

If none of these boxes have been run for a long time the valves can stick in the body. Easily cleaned and unstuck. I have a rebuild manual for all GM boxes somewhere. It's very easy, i did a th350 in a bedroom with only basic tools and some circlip pliers.

Hi, I've used the engine before but not the gearbox, so I can make a few observations. If the box it vacuum controlled there's a vacuum control valve goes on the throttle shaft to regulate vacuum to the modulator unit. As the engine doesn't naturally produce vacuum you will need a vacuum pump and maybe a small reservoir to give the valve something to control. On other auto g/boxes like the Borg Warner the shift into top is controlled by a governor on the tailshaft and they can stick.

As an aside, if you're thinking about it, the Stanadyne pump is not keen on veg oil. At least mine wasn't it caused minor surging on a steady throttle.

Colin

Thanks for the replies guys. frag, These have a solenoid-activated kickdown, no cables, and the solenoid's firing fine.
drdick, I reckon you're on the money with the sticking valves, that's what I keep coming back to, both from what I hear and what I read on the tinterweb. I got the box from a guy who builds hotrods near Fleet, he certainly knew his onions, and was fitting this same engine and box into a pickup while I was there. This box came off the back of the same engine, and has the adjustable modulator, but from what I've read the modulator can only alter the shift point slightly, and with it the severity of the shift. The box should shift eventually even with it disconnected.
colnerov, there's a big diaphragm pump at the back of the engine, which goes through a doohicky on the throttle shaft of the pump. this decreases the pressure to the modulator as the throttle opens, and I've had that apart and cleaned it, and it seems to be playing ball. I also had the governor out, and disassembled it as there was some curse word stuck in it causing it's little valve not to move. That's another thing pointing to sticky valves. I really reckoned that I'd flushed it pretty well, having spanked the best part of 25l through it for one reason or another, but I guess that there can still be curse word in the torque converter. The oil that came out of the old box was pretty lumpy and nasty. Another flush, and if that doesn't work a disassembly of the valve block seem in order. Cursed bank holidays don't make things easier though!
I'm pretty certain that these boxes are the same whatever they're hooked up to dodgerover, it's just the bits and bobs that differ - final drive, speedo gear, modulator, and governor weighting. But this box shouldn't be needing any changes of these bits, as it came off a similar engine.
I don't reckon I can hang around for another two days, so I might have to get it recovered and deal with it after my next job.

Cheers for the thoughts guys

Yeah, that's the one! It had grills over the windows and loads of blacked out panes from use as a prison bus in a film, but it made it too gloomy inside so they've gone. It'll be great when it all works, and it was cheap enough to make it worthwhile, but there's more to do than how it was described!

It's hard copy I'm afraid and currently at my mates house but I could get it for you if you really want it. I would guess you can drop the valve body out but I'd be wary of doing that without checking a manual or something first because there are often balls and springs sandwiched between the two parts of the body and they could easily disappear......

It's a thought that's crossed my mind, but the likelihood of getting that done before festival season kicks off is slim to none, especially if I want to finish any of the other things I've got to do before then. It's very appealing though...