Auto Box Newbie

[Rossco]

Ok, I can find my way from one end of a V8 to the other.......and back again

But auto boxes were always the children of Satan as far as I was concerned.

However, now I'm about to become a devil worshiper I could do with the auto gearbox 101.

The TH400 I have is a full auto box, no manual shifting. But I can buy a manual shift kit. So I have. This kit makes it a kind of semi-auto with no shifting until I stir the lever.

Also bought a full rebuild kit.

So now to the question. How the blinkin' 'ell does this kit work? In other words how does stirring the auto lever make the box switch gears?

Told you it was a newbie question

[ian.stewart]

http://store.summitracing.com/egnsearch ... &N=700+115

[Rossco]

Thanks for that......but I've already purchased the kit.

Just need to know how the bloomin' 'ell it does what it says on the packet.

[ChrisJC]

I know how an auto box works, is that what you mean?, or do you mean how does the manual shift kit work (which I don't know).

Chris.

[Eliot]

I fitted a reverse pattern manual VB on my Dakar on someone else’s advise to solve a particular problem - Tried it and removed it - Only any good for the strip in my opinion.

Problems i encountered:
1) If you select the wrong gear (1st instead of 3rd on a 2-3 shift) it does it - and all your wheels lockup!
2) No more kick-down, so no floor it and snap past a car. You could downshift, but you need to be very careful that you don’t over-rev it on the downshift.
3)My tci vb for the 700r4 ran full line pressure all the time - so neck snapping lightning fast shifts even when pootling around - gets boring very quickly. Which also blew the snap-ring out on the input drum.
4)And why have an auto that’s a manual? - worse of both worlds (unless drag racing)

How do they work? - Difficult to explain really, basically a load of epicyclic gears engaged by hydraulics with wet clutches.
Each change is transitioned by the clutches (and sometimes bands, to grab the outside of a drum) so if you don’t have enough clamping pressure they will slip and burn up. Most shift kits increase the pressure and speed that the clutches apply, as performance people want them to engage quicker and sharper.

You mustn't go too far with harsh changes though, because it becomes tough on the box. Some shift kits remove internal accumulators to make the shifts bang - but this isn't a great idea, firm them up - but don’t bang through them

My preference is Transgo shift kits (they invented them and hold the trademark on the description "shift kit") - the B&M ones are essentially copies in fancy packaging with a higher price and are called "shift correction kits". The B&M ratchet shifters are good though.


http://en.wikipedia.org/wiki/Epicyclic_gearing
http://auto.howstuffworks.com/automatic ... ssion.htmv

As for rebuilding them - don’t be afraid. You need plenty of clean space to lay it all out in the order you took it apart and take plenty of digi photos.

I rebuilt a Th350 using ron sessions book, which was excellent. Looks like he has one for the 400 too:


672036&sr=1-3

Get the ATSG guide to, it’s for professionals - but is very handy alongside any other books:

http://www.atsg.biz/cgi-bin/shopper.cgi ... icecode%3D


best to pull it apart first to figure what you need, but generally - a full master rebuild kit (which should include all clutches, steels, bushes, bearings and all seals) will rebuild all but the most trashed box.