73-87chevytrucks.com
73-87 Chevy _ GMC Trucks => Suburbans => Topic started by: Deercreekfarm on June 09, 2019, 12:55:14 PM
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It’s been a while since I’ve posted but I have a new toy;
I bought a 1991 Suburban V2500 4X4 with a 6.2L Diesel with Barn Doors on the back. Everything is factory and I call it my unicorn find. Here’s my question, what all is needed to remove the Gen 1 EDM (PCM) from the truck? I know I will need to ditch the 460LE transmission for an older non electronic TH350 or TH400. Has or does anyone know what all I will need to change, swap, add and or delete to do this?
Thanks
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91 Suburban did not come with a 4L60E and why do you want to remove ECM?
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Well it might not have come with a 460LE but that’s what it’s got in it. I thought they come with 700r4’s and I want to get rid of the ECM and put everything back to mechanical. I’ve owned numerous 85-87 models and never had a problem. Had a 1990 with ECM and had nothing but problems the entire time I owned it. I found this one rust free not abused and owned by Duke Energy so it was well maintained and cared for close to the level as the government used CUCV’s. I’m no spring chicken so I would like to get this thing set up to last me the rest of my life.
So has anyone had experience doing this before? Just looking for a little guidance.
Thanks,
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91 Suburban did not come with a 4L60E and why do you want to remove ECM?
What overdrive trans did they use in the 3/4 ton trucks in 1991?
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I thought they used TH700r4’s but it has a 4L60E in it.
I’m thinking get rid of the intake and replace it with an 85 or earlier and drop a 350Turbo in it and that should eliminate everything connected to the ECM, I think?
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As far as I know the 6.2 never came with a turbo 350, so you would be on your own with the kick down linkage.
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Well I’m not sure of anything that’s why I’m on here trying to get some answers but instead all I’m being told is what I don’t no which is admittedly nothing about how to even attempt this.
Just looking for any help, advice from someone who’s done this.
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Any chance it's actually a 4L80 in your truck?
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Could be. I will have to crawl under it and look at the bolt pattern of the pan. When I bought it I was told it has the 4L60E in it. Knowing I want to ditch the ECM I wasn’t to worried about it because I figured it was coming out anyway.
It’s been years since I’ve messed with these trucks but if I remember correctly every trans from the TH350?to the 4L80E all have the same bolt pattern to mate up to the motor correct?
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Yes.
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91 Suburban did not come with a 4L60E and why do you want to remove ECM?
What overdrive trans did they use in the 3/4 ton trucks in 1991?
700R4/4L60 or 4L80E
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If it's a 3/4 ton, then i think a 4L80 E.
Does the computer/ECM even control anything on a 6.2 diesel?
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I crawled under it and it is a 4L80E transmission in it. The guy I bought it from obviously didn’t know what he was talking about.
My understanding is that the ECM controls throttle and shift points. Maybe someone anyone knows more than me and will chime in here.
As I mentioned before I want to delete the ECM and put everything back to mechanical. Just wanted to see if anyone had done that?
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you need a computer to shift that trans, doesnt have to be the ecu but it needs something. you can get a standalone box for it but they do cost $500+. its been some time but i thought the ecm on those is pretty much a stand alone computer and only reads inputs from the tps and rpms. i picked one up (ecu and wire harness for a 6.2 and 4l80E) a few years ago but never got around to messing with it. so why do you want to get rid of that trans besides the bad luck in the past?
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I’ve had 85-87 year suburbans and the things last forever. I had a 90 suburban with the ECM and literally spent more time under the hood than behind the wheel and it always led back to the ECM. I found this 91 (last year of the square body) rust free, 4x4, 3/4 ton, diesel with barn doors and plan on keeping it but don’t want to fight with the stupid computer. I would like to delete it and do whatever it is I have to do to the engine and swap out the trans for an older mechanical model.
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that ecm is only going to power the transmission, you wont have any worries about the ecm and engine like you did before. on top of all that the 4L80e is going to be a lot stronger and more reliable OD trans in my opinion. that being said if you want to swap out the trans youre going to need to find one with an electric speed sensor or your speedo wont work right. the transfer case you have now will be a 32 spline and its the only OD trans thats a 32 spline besides a later model manual trans. the 700r4/4l60 will be 27 splines. you might be able to find a 700r4 and transfer case out of 89??? (cant remember what year they started the electric speedo), but then you need a new front and rear driveshaft unless you find that setup in a burb. im going to add one last thing, i have that setup in my 91 v3500 crew cab with a cummins in front of it, and i abuse it. i did away with the ecm as the cummins was a first gen and i didnt have the right sensors to run the stock ECM. the "black box" i installed lets me manually shift the 4l80e at the cost of full line pressure. so this trans is really getting abused and used.
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Your 87 suburban had an ECM unless someone removed it.
The 6.2 in your truck is a mechanical engine. All it needs is 12v to the injector pump to be happy.
Irish covered the 6.2/4L80 computer set up, I wont beat a dead horse. I will say I'd if you remove that 4L80 set up from your truck, sell it on Ebay. Lots of guys want that set up.
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i know i would want it even if it just sat in the car port with my other cummins engine lol
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Thanks for the feedback. Let me weigh my options here and come up with a plan.
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4L80e is pretty much bullet-proof! I would keep it. Plus you have overdrive which is key for these old trucks in making them much more enjoyable to drive!
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I feel your pain DeerCreeker!
Since it's been verified that a 700R came stock, I would go in that direction.
As far as the electronic control of that trans, there are aftermarket parts that accomplish that, and best of all, you control it.
The bonus of an overdrive is what I would find most interesting.
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(https://uploads.tapatalk-cdn.com/20191124/e3d87bf1a902d8c8d458abf248d6a1a6.jpg)
Here’s a pic of the suburban. I removed the step rails / nerf bars and replaced the front bumper with a stock bumper. Have 3 or the original hub caps, just missing a front one.
I got it at what I thought was a great deal for a rust free 3/4 ton, diesel with barn doors (what I’ve always called m unicorn burban). I’ve owned a 1990 3/4 ton with barn doors but with a gas engine. An 1987 Diesel 1/2 ton with a tailgate but always wanted a 3/4 ton, diesel with barn doors.
As mentioned in another post I got the over heating problem worked out with new radiator, thermostat, water pump, fan clutch and new head gaskets. When I bought the truck the guy said it needed tranny work. The only problem with it is the OD is not working. Any ideas or am I looking at a tranny rebuild? She drives great and runs smooth just no OD.
Let’s see if I can get the tranny figured out then it’s on to some 1 ton or 5/4 ton axles, lift, wheels and tires then to the paint shop and onto the interior.
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(https://uploads.tapatalk-cdn.com/20191124/d10b57d683fa480e428cdea01981ea74.jpg)
Here is a pic of my old 1987 with a 6” lift running 36’s
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(https://uploads.tapatalk-cdn.com/20191124/8a9b078d9421488d429ebf1d705da567.jpg)
Here’s a pic of the 2003 3/4 ton barn doors gas engine I had gotten for my son.
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Question on the 4L80E no overdrive;
So as I mentioned the tranny has no OD. Called around and all the shops want to do a total rebuild and the cheapest quote I got was $1,200.
I found a married 6.2 engine J code in front of a HD TH400 Turbo with an NP208 out of a military CUCV in good running order all 3 for less than a rebuild on the 4L80E. I know the 400 doesn’t have OD either. It is the HD military version and I would have a spare J code NP208 (off my 91) and I guess my 4L80E.
Here are my questions;
How hard would it be to swap to the 400?
What would I need to do the swap?
Would it be better to rebuild the 4L80E?
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Better to rebuild the stock trans and keep the OD (that you don't enjoy now)
I'm not familiar with that trans- is the OD controlled by a processor? If so, have you checked out that angle? Is it as simple as 12v going to a valve/servo?
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Thanks for the input JonnyPopper. I may just go ahead and do the rebuild on the 4L80E like you suggested. Wife would be pooping kittens if I brought another engine, trans and t-case onto the farm.
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Adding a 4L80E to an older truck is a common conversion, and there are quite a few articles out there about the conversion. I assume in '91 it was controlled by the computer, but in many conversions they use an add-on controller. I would read through a few of the conversion articles to figure out how the overdrive should be controlled, and you may find a simple fix to get it working.
Bruce
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91 is computer controlled for the trans but the engine is another issue. its been a few years but i know gm used basically a tcm that was pretty much a standalone computer as it would only receive signal from a few sensors on the engine as the 6.2 and think the 1992 6.5 didnt need a computer to run.
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Adding a 4L80E to an older truck is a common conversion, and there are quite a few articles out there about the conversion. I assume in '91 it was controlled by the computer, but in many conversions they use an add-on controller. I would read through a few of the conversion articles to figure out how the overdrive should be controlled, and you may find a simple fix to get it working.
Bruce
Yeah it already has the 4L80E in it and I was considering stepping back down to a TH 400 Turbo but think I’m just going to rebuild the 4L80E
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91 is computer controlled for the trans but the engine is another issue. its been a few years but i know gm used basically a tcm that was pretty much a standalone computer as it would only receive signal from a few sensors on the engine as the 6.2 and think the 1992 6.5 didnt need a computer to run.
Yeah this is why I was wanting to go to the older 6.2 with the 400 turbo trans so the engine and trans is all mechanical and I take the computer(s) out of the loop.
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I do know it has the OBD1 port on it. My 1990 burban had the same thing but it was gas and the 87 did not have an OBD1 port.
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Got my CUCV bumpers and brush guard put on the Burban. I also mounted my hi-lift jack to the front.
(https://uploads.tapatalk-cdn.com/20200418/fe47851a45d14a777291fa1c54000ffe.plist)(https://uploads.tapatalk-cdn.com/20200418/388f7f57191b835c7a93291549c8c753.jpg)(https://uploads.tapatalk-cdn.com/20200418/b7f3128cdc3646765e430882053119bc.jpg)
I also put in a new dash cover, radio and new front seat. Next will be the 4” lift wheels and tires then off to paint.
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Nice bumpers.
I'm a huge fan of CUCV's.
Do you plan to tow with that pintle hitch? I'd check it out first. Someone's done some custom work to that hitch. That's not the factory set up.
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Nice bumpers.
I'm a huge fan of CUCV's.
Do you plan to tow with that pintle hitch? I'd check it out first. Someone's done some custom work to that hitch. That's not the factory set up.
Oh yeah I double checked it. The receiver hitch was on the Burban when I bought it. I had it off when I was installing the rear bumper and inspected all the welds. It’s really beefed up. I was going to put the old receiver hitch off my K5 I sold but I likes this one better.
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Put the roof rack on this weekend. She’s coming along. I guess the lift will be next.
(https://uploads.tapatalk-cdn.com/20200504/86c54030fd56bde15cee614f5fd06cdc.plist)
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roof rack b4 paint?? :o
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roof rack b4 paint?? :o
Of course! I wanted to fit and measure everything, drill my holes and mount it. Now when it goes into paint it will take me about 30 minutes to an hour to disassemble and about the same to mount it back on when she comes back from paint. If I would have tried to do this after paint I would have had scratches everywhere.
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Good call man! Look forward to the finished product!
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I have a new issue that has started; since I’ve had the truck she has just floated down the road like a caddy. Yesterday out of the blue she started bouncing/vibrating at 40mph and up. It may be at lower speeds but I can’t tell. I thought maybe one of the wheels lost a weight and was out of balance but everything looks in place.
Any ideas as to what it might be or what I can check next?
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Does it currently run OK right now? If yes, why not wait till there is a problem to make changes?
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Dana 60/44 death wobble. Do a search for it. Probably need new kingpins. Very common.
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Does it currently run OK right now? If yes, why not wait till there is a problem to make changes?
Yes, she runs like a champ! Not sure why I should wait until there’s a problem to make changes? There is a problem; she went from driving like a Cadillac to driving like a dump truck. I’m not going to wait until the wheels fall off to fix it. I’m trying to stay out in front of the issue. I learned a long time ago that the longer you wait to address an issue, the more it’s going to cost to fix.
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Does it currently run OK right now? If yes, why not wait till there is a problem to make changes?
Yes, she runs like a champ! Not sure why I should wait until there’s a problem to make changes? There is a problem; she went from driving like a Cadillac to driving like a dump truck. I’m not going to wait until the wheels fall off to fix it. I’m trying to stay out in front of the issue. I learned a long time ago that the longer you wait to address an issue, the more it’s going to cost to fix.
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Does it currently run OK right now? If yes, why not wait till there is a problem to make changes?
Yes, she runs like a champ! Not sure why I should wait until there’s a problem to make changes? There is a problem; she went from driving like a Cadillac to driving like a dump truck. I’m not going to wait until the wheels fall off to fix it. I’m trying to stay out in front of the issue. I learned a long time ago that the longer you wait to address an issue, the more it’s going to cost to fix.
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Does it currently run OK right now? If yes, why not wait till there is a problem to make changes?
Yes, she runs like a champ! Not sure why I should wait until there’s a problem to make changes? There is a problem; she went from driving like a Cadillac to driving like a dump truck. I’m not going to wait until the wheels fall off to fix it. I’m trying to stay out in front of the issue. I learned a long time ago that the longer you wait to address an issue, the more it’s going to cost to fix.
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Mike81K10 -
Yes, she runs like a champ! Not sure why I should wait until there’s a problem to make changes? There is a problem; she went from driving like a Cadillac to driving like a dump truck. I’m not going to wait until the wheels fall off to fix it. I’m trying to stay out in front of the issue. I learned a long time ago that the longer you wait to address an issue, the more it’s going to cost to fix.
Mr. Diesel -
Yeah I’ve dealt with death wobble before (on my lifted trucks never stock) but it doesn’t feel like that. Doesn’t mean it’s not that either. I have a 4” lift I want to put on it and was going to replace the passenger side knuckle/kingpin for a crossover steering set up. If that’s it then I will need to go ahead and install new driver side as well. I’m wondering if I may have a U-Joint going out. Just feels like the hole truck is rattling. Not bad but over night she went from smooth to rough.
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Mike81K10 -
Yes, she runs like a champ! Not sure why I should wait until there’s a problem to make changes? There is a problem; she went from driving like a Cadillac to driving like a dump truck. I’m not going to wait until the wheels fall off to fix it. I’m trying to stay out in front of the issue. I learned a long time ago that the longer you wait to address an issue, the more it’s going to cost to fix.
Mr. Diesel -
Yeah I’ve dealt with death wobble before (on my lifted trucks never stock) but it doesn’t feel like that. Doesn’t mean it’s not that either. I have a 4” lift I want to put on it and was going to replace the passenger side knuckle/kingpin for a crossover steering set up. If that’s it then I will need to go ahead and install new driver side as well. I’m wondering if I may have a U-Joint going out. Just feels like the hole truck is rattling. Not bad but over night she went from smooth to rough.
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Kind of early to be drinkin
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Kind of early to be drinkin
Tell me about it!!!! LOL
Actually an error message kept popping up saying the server is not responding so I would hit cancel and try again and again. When it finally went through I had sent it 4 or 5 times.
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Update! So took the tires to check if they were in balance and one had busted radial band and was the culprit. From outside everything looked good but tire would not balance. Replaced tire and she rides like a Cadillac again.
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Oh if only all the square body's rode like Cadillac's !!!
Guess there's a price for holding on to stock gear and the recent past.
When peeps ask me about "mileage" I smile and say it's a small cost for a piece of the past...