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90 cc and tbi 454 on 89 Suburban frame

tonyjohannson

tonyjohannson

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First time poster. Done a lot of reading, but could not find the answer I was looking for so here it goes. I recently purchased a 90 Chevy cc dually 2wd with a 454 tbi 4l80e. Ive wanted a cc for ever and finally got a chance to pick one up cheap cuz its 2wd. I plan on putting the cab and motor on an 89 4x4 Suburban frame one cuz I already have the frame, and second cuz I want the shorter wheelbase. I Am gonna leave the harness and brain box on the cab when I swap it to the suburban frame, I plan on using the 700r4 currently in the suburban for the time being. My question is with the brain box being setup for the 4l80e if I just disconnect it and leave it are there gonna be any problems?? Also I don't believe they will but will the 700r4 converter bolt up to the fly wheel on the 454?? May be newb questions but just tryin to get an idea of what I may run into. Thanks in advance
 
The 454/4L80E computer will not control the 700R4. There wasn't a stock computer that ever mated the 454 and 700R4, but you can try an aftermarket lockup kit for the trans. I'm not sure if there's a difference on the tq. conv / flexplates. I would keep the 4L80 if at all possible, it's much stronger and will be worth it if you can mate the tranny to t-case.
 
Im aware the computer will not control the 700r4, I already have how Im gonna do the converter lock up figured out. My question is if I disconnect the 4l80e wiring and leave it hanging is it gonna throw any codes or will it be fine. Id use the 4l80e but its a 2wd tranny and it needs rebuilt. For ease of what im doing right now Im gonna just use the 700r4 cuz I have enough of them sitting around and its not gonna cost me a dime. Itll get a beefier trans down the road when I decide standard or auto. Thanks for the info Jason!
 
Yes, it will throw codes. I would assume (not having dealt with the 4L80E) that the PCM will have logic in it that will try and "save" the transmission, thus decreasing engine performance in that attempt. Could be wrong, one of the bright trans guys here will know for sure.

Don't know about the ECM/PCM connector interchangeability, but the 1227747 ECM would work on that setup pretty well if it was from a 454/TH400 application. I *might* have access to one of those PROM's if you figure out if the 1227747 would work in your application...
 
I guess if it comes to it I do have the harness and brain box out of the suburban for the 350/700r4. Ill have to get a new Chip and change TPS and IAC connectors but if the 454/4l80e computer will give me fits ill just swap em out. Thanks dyeager535
 
Put a 4wd tailshaft into the 4l80, thats a great transmission.

I don't think you will have any problems going the 700 route but you might have to delete certain things off your computer. Not sure if you can do that or not. Only to prevent the check engine light from coming on
 
'90 w/ 4l80e? Swapped in?

'91 is the first year for a square body.
 
If swapped in, any chance they didn't swap the harness over and you have an older harness/ECM??
 
Thatd be nice.. Im out of town with work right now so cant look any deeper into it. Does anyone know if thered be a way whoever did the tranny swap set it up without changing ecm?? Any way to run a stand alone type computer for the 4l80e
 
There are aftermarket, stand alone controllers.
 
The early diesels (and HMMWV's) used a standalone TCM, and I think you can buy an aftermarket controller, but they are stupid expensive last I saw.

No way it will work right (at least electronically) without a proper PCM/TCM or aftermarket "brain".
 
That's what I thought just wasn't 100% sure. Well maybe Ill get lucky and whoever did the swap used a stand alone controller and left factory ecm in truck. Haha now I just wanna get home so I can check it out
 
No matter what they did unless absolutely butchered, you probably didn't do bad. If it is a factory setup, just pull it and save it for later, if it's aftermarket thats good too.

But aftermarket TCM combined with TBI wouldn't make any sense, since obviously TBI and 4L80E could run off the same PCM. Might work ok for what you have going (since you have a 700) but outside of that, would be a surprising combination for someone to attempt.
 
Well theres also a really good chance it is a 91. Ive seen and driven the truck but didn't do any looking at vin and title. The guy I bought it from swore up and down it was a 90 but we all know how intelligent some people are now a days.. Ill give the guy a call and see what he says and have a buddy swing by and get me the vin so I can check it for sure
 
Maybe the guy just looked at the manufacture date in the door jamb, that could be in '90 as each model year typically starts in the preceding sept..
 
nvrenuf you were completely correct :bow: he looked at the door and assumed it was a 90 even thou he had the title that said 91.. It is a 91 according to title and vin..
 
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