1991 drivetrain into a 1982

[Galane]

I have a 1982 GMC Sierra 3500

https://www.flickr.com/photos/27748767@N08/sets/72157644959205217/

350, 4.56 rear gears, no AC, no cruise, no dome light, no nothing but power steering, power brakes and automatic transmission. (But it does have an AM/FM radio, such luxury!)

I've pulled a running 350 with TBI and 700R4 from a 1991 standard cab Chevy 2500. Got the engine wiring that goes through the firewall and to the ECU, and the ECU. Didn't grab other things that connect to other connectors in that harness, if there's some of that I need I can still get it for no extra $.

Question time. The 91 has the electronic speedometer.
How can I retain that input for the computer AND drive the 82's mechanical speedometer?

I've heard there are ways to eliminate that input but also that the TBI works better and will have better MPG with the speed input. This swap is all about improving MPG and reliability. The extra horsepower over the 1982's 160 will just be a bonus.

Is there a 4-speed shift indicator I can retrofit in place of the original 3-speed one?
Do I need to change anything in the column shift?
What about the neutral/safety switch?
Will the 91's ECU chip need reprogrammed for the 4.56 ratio? (OD will drop final ratio to 3.17.)

Any mechanical bits won't be a problem. I can build, buy or farm out all that. Changing the driveshaft length is as easy as taking it to Connie's and telling them how long to make it.

I've done plenty of engine and transmission swaps on cars from the 40's to the 00's and one non-electronic 700R4 into a 1978 Chevy van, but this is my first go with stuffing a drivetrain with electronic systems into a vehicle that barely has any transistors - just electronic ignition and the radio.

 

[RetroC10Sport]

1990-91 Squares got an electronic speedometer and the 4 speed indicator so I might suggest one of those as they aren't super hard to find.

 

[Galane]

I've found these http://www.jagsthatrun.com/Pages/SpeedSensors_Speedometer.html The 1991 TBI should have the two pulse per revolution type.

Smog systems on this truck are not a problem due to 1. I'm not in California. 2. It's a one ton and even in California it was exempt from all the CARB regulations when it was new.

 

[marks86]

wouldn't a 91 2500 truck have a 4l80e from the factory?

 

[MadOgre]

nope I had a 92 2500 with a 350/700r4/np241.

You can buy the mechanical cover ring gear and speedo housing at any gear shop that sells rebuild kits for the np241. 89 np 241s used the speedo cable so either find one at the junkers or buy the parts. I believe your link is for converting a cable setup to electronic not the other way around.

If your running the factory ecm for your tbi your gonna wanna keep your electronic speedo setup. So your best option would be to get the gauge cluster and necessary electronics out of a 90-92 burb

 

[marks86]

nope I had a 92 2500 with a 350/700r4/np241.

You can buy the mechanical cover ring gear and speedo housing at any gear shop that sells rebuild kits for the np241. 89 np 241s used the speedo cable so either find one at the junkers or buy the parts. I believe your link is for converting a cable setup to electronic not the other way around.

If your running the factory ecm for your tbi your gonna wanna keep your electronic speedo setup. So your best option would be to get the gauge cluster and necessary electronics out of a 90-92 burb

I have to say I really thought 700r4 were half ton transmissions, never hurd of them coming in a 2500 or 3500

Im pretty sure 91 2500 or 3500 truck got u a 4l80

 

[MadOgre]

I have to say I really thought 700r4 were half ton transmissions, never hurd of them coming in a 2500 or 3500

Im pretty sure 91 2500 or 3500 truck got u a 4l80

92, 2500 = 350/700r4/np241 that's what it was

 

[Galane]

The transmission only has a 2 wire connection for the speed sensor and the 4 wire plug.

I've found instructions on converting the various electronic speedo setups to a mechanical type. Looks like it mostly involves pulling the reluctor off the shaft, installing the drive gear and replacing the tail housing. Then I can attach one of the #1 2 pulse/rev adapters from that Jag site, unless there's another place with a lower price.

Replacing the entire instrument cluster would involve more wiring, possibly involving removal of the dash to install it.

Then there would be calibrating the electronic speedometer. How is that done?

Will anything need to be reprogrammed in the ECU's chip with the add-on speed sensor and using the mechanical speedo?

I got the JTR conversion manual, will be reading that to see what it has to say.

I need to find which speedo driven and drive gears are needed to work with a 4.56:1 axle ratio and 235-85R16 tires.

The 3 speed transmission had been worked over or replaced at least once on the 1 ton, apparently the wrong speedo gears were used because it reads over 5MPH fast at slow speeds and is still almost 5MPH fast when GPS reads 60MPH.

I'm going to see about getting a tilt steering column out of a slightly newer GM truck that had the 4 speed so I'll have the tilt and the proper 4 speed shift indicator and the neutral safety switch too if that's different.

On looking up parts I've found many websites do not show a 350 for a 1991 2500, only the 4.3 V6 and the 454 V8. Wheee. Yet again I am in possession of something "nonexistent" - according to some sources. Of course they're wrong but try to convince them of the truth...

I've run into many such things, rental fleet vehicles with various options never available to the general public, or lacking things regular sales vehicles had. How about an engine in a 2004 with a block and front cover type supposedly discontinued mid 2003 yet the valve covers, heads and various other bits are all 2004? Yup, rental fleet *cough*Dakota*cough*. I get it often with computer parts where the manufacturer denies ever making an item that has their name, logo, WWW address, physical address, FCC ID and phone number stamped on it. They sell "reference design kits" so the "manufacturer" just solders the thing together and *neither* company will provide support.

 

[MadOgre]

The transmission only has a 2 wire connection for the speed sensor and the 4 wire plug.

I've found instructions on converting the various electronic speedo setups to a mechanical type. Looks like it mostly involves pulling the reluctor off the shaft, installing the drive gear and replacing the tail housing. Then I can attach one of the #1 2 pulse/rev adapters from that Jag site, unless there's another place with a lower price.

Replacing the entire instrument cluster would involve more wiring, possibly involving removal of the dash to install it.

Then there would be calibrating the electronic speedometer. How is that done?

Will anything need to be reprogrammed in the ECU's chip with the add-on speed sensor and using the mechanical speedo?

I got the JTR conversion manual, will be reading that to see what it has to say.

I need to find which speedo driven and drive gears are needed to work with a 4.56:1 axle ratio and 235-85R16 tires.

The 3 speed transmission had been worked over or replaced at least once on the 1 ton, apparently the wrong speedo gears were used because it reads over 5MPH fast at slow speeds and is still almost 5MPH fast when GPS reads 60MPH.

I'm going to see about getting a tilt steering column out of a slightly newer GM truck that had the 4 speed so I'll have the tilt and the proper 4 speed shift indicator and the neutral safety switch too if that's different.

Its super easy taking out the dash it takes like 5 min. If that!

I see so run a mechanical for the speedo and then also run the pulse for the TBI ?

Tilt is nice but you only have to remove the dash bezel and then 2 more screws removes the column indicator, the cable for the indicator is just a clip board style/ friction fit clip that clips to the actual column. so just pull it off with your fingers. Its pretty simple.

Also the column doesn't house the indicator the instrument cluster does.

I have to replace my pulse style NP241 with the mechanical.

Im not sure about setting the electronic speedo but I do remember seeing a guy doing it on youtube