I read the tech article on converting from efi to carb. It looks pretty straight forward however I have a few questions.

Since I'm considering doing this on my truck it's not an f-body but still GM. The tranny is a 4L80E that needs a computer to control it. Did the f-body have a computer controlled tranny after the 700R4 changed designation?

If so then does the carb/ignition conversion affect the ECM's ability to operate the tranny?

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87 IROC-Z SuperPro ET Bracket Race Car
461 naturally aspirated Big Block

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87 IROC bracket car, 91 454SS daily driver, 95 Homebuilt Harley

 

Steve, the only thing the ECM controls on any F-body auto box is the TCC Lock up.

I assume you want to retain the 4L80E but installing a carb still requires an ECM (or PCM depending on year and engine of the truck). It is feasible to "reprogram" the ECM to handle "just" the tranny portion, but it is beyond the typical "DIY PROM" burner's capability. It requires disassembling the machine code and then "cutting and hacking" the code so only the relevant parts remain. Not something you'd want to try for your "first project" in DIY Programming.

The second possibility is a "stand alone" ECM just for the tranny, like from JET. This is the common solution for guys who want to run a 4L80E in an older vehicle that never came with a 4L80E (or even an ECM).

 

If the computer only controls the converter lockup then you could theroetically just rip out the entire computer harness. The only thing you'd have to do is wire up a switch for the lockup.

Unless, of course, the computer does more than just lock up the converter, which I'm kind of getting the impression it does since Glenn mentioned the JET unit, then you'll have the buy that.

I did use a 4L60E converter in my 700r4 and had no problems with it though...

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1990 GTA
-355 carb'd, nicely reworked '64 vette heads, 2500 stall, 4.10's, other small things.
-Alston SFC's, Eibach Pro-kit, Koni's all around
-100+ nitrous shot
-Cruising in style with leather and nice stereo.

 

The ECM controls all aspects of shifting on the "E" versions. The non-E versions are still "manual" but have locking TCC.

While there are E and non-E versions of the 4L60, I believe all 4L80s are E versions.

Steve, check out JET and their stand-alone computer.

 

Just wondering that's all. I'm aware of the JET computer. The 4L80E needs a computer to operate, not just converter lockup. Theoretically you could make a push button tranny with it. All the shifter does is move an electronic control in the valve body and the computer does all the shifting. Incorporate something like a forumula one shift paddle system on the steering wheel and eliminate all the extra linkage.

The 4L80E is an electronic version of the TH400. About 80% of the parts are the same. As much as I would like to just switch to carb and install a TH400, the OD is a nice feature when you have 4.10 gears.

 

It'd have to be more complicated than that, the computer controls line pressure too.