Edelbrock 1407 with TH400

[Longhorn Man]

I am by no means a tranny expert.
With that being said;
I have NEVER heard anyone ever even imply that the TH400 was the same as any of the other trannys that you listed.
A 2 speed jet away has very little in common with a TH400, except for theory of oporation, and if we are going into theory of oporation, we may as well call it a C6 or put a dodge logo on it. A 4l60, or 4l80... and esp the E versions of these 2 trannys, are very complicated pieces, and are distant cousins, if anything,to the TH400.
The kick down button shown on the lead photos is correct. All the 67 - 70 GM trucks that came with a TH400, also came with that button. Starting in 71, when GM went to a cable type throttle contolr, they installed a slider type switch under the dash on the accelerator pedal.

[KFreddy]

Longhorn Man,

I've been itching to get back to this thread for some time now, however work had me out of state with almost two 70 to 80 hour work weeks, hence the lack of time or energy to respond.

Somewhere between "distant cousins," and semantics the Th400 had many incarnations. Are they exactly the same? No, but aside from nomenclature the, 2-speed Jetaway, 3-speed Super Turbine 300 (ST300 or 300THM,) 3-speed Super Turbine 400, Th375, Th425, 3L80 and the 4l80e are more so brothers then cousins. The 200-4R, 700R4 and 4l60/ 4l60e are not part of this lineage as they belong to the Th350 "light duty" transmission line.

What I know and believe is that the Th400 family including the current 4l80e share much more the the "HD" badge. They share parts, many parts for that matter. A short list could include the forward clutch hub, reverse bands, direct(high gear) drum, case bushings, front spline seal, rear band, center support, forward and direct clutches and the intermediates (4 vs. 3,) they both have 34 element sprangs. The case bushings are different only because the 400 uses the oil bleed for a mechanical spedo whereas a 4l80e gets it's spedo info from a bushing fed pressurized tube. They also share the same TQ converter size, 12.20", and also have the same 1-3 gear ratios. The 4l80e simply has an extra planetary for 4th gear/ OD. In stock form both transmissions have the exact same Engine TQ rating - 440 and Gearbox TQ rating - 885.

Where as the Th400 uses vacuum input to shift the 4l80e uses input from a throttle position sensor vs. speed = RPM as it's shifting "brain." Someone with savvy electronic skills could use a $100.00 "smart" relay with 16 digital I/O and 2 analog inputs in conjunction with a Transgo shift kit and basic a TPS and have a 4l80e work seamlessly with a carburetor engine. There by negating the need for a $1000.00 +++ stand alone computer to do the 4l80e's shifting.

My point wasn't to open a can of worms, just to show a correlation within the Th400 family. In essence the same differences apply between the first 1914's L-Head Cadillac 314ci V8, Chevy's 265ci, OHC V8, and a modern LS7, they are all incarnations of the same excellent idea.

[mnunn454]

Originally Posted by KFreddy

.....Secondly for the kick down switch. There are two tell tale ways of knowing what Th400 you are working with. See pictures below: If you have two connections on your Th400 it is an earlier model, hence the use for a vacuum carb activated detent switch that activates the converter pitch. So one connection is for the converter pitch and the other connection is for the kick down switch. IDing your tranny will tell you what type of detent switch you should be using, peddle activated or carb activated.

Keep in mind that everything I say might be wrong

Kfreddy, This thread is very informative, and not to jump on the "pick on Kfreddy bandwagon", but I again have to take exception to a statement of yours (I bolded it above).

I just cleaned off the 72 vintage Chevelle TH400 in my truck and reinstalled it behind the 454. While doing so I noticed the electrical kickdown connection in the tranny had 2 male spade terminals arranged in a T shape. It's not B.O.P. or Caddy so it isn't variable pitch. The ID tag clearly nails it as a 72 and the thing definitely has 2 terminals (though the vertical one is hard to see in the picture below). Looking inside it with the tranny pan off, it only has a single wire going to the kickdown switch.

Point is you (I in this case) can't count the terminals and draw the conclusion it's an "an earlier model" TH400 (depending on how you define "earlier, of course). I did that initially and was disappointed when I thought I had a variable pitch tranny and didn't.

[blukangoo]

Thanks again for the answers.
Can anybody translate this stuff?
My Switch only has one connector.
It looks just like the switch in the picture from mnunn454 but I only have the bottom connector.