89 Silverado 700r4 to 4l80e swap

[618 Syndicate]

Wouldn't it be a pre-electronic injection 6.5td (and 6.2 of course) that just has a standalone transmission controller? In that case it would be 1991-1993 diesels only.

Richard

I think you're right.

 

[Nad_Yvalhosert]

Thanks, do I have to change the harness under the dash?

No, the 94 4l80 engine side harness will pull through from the ECM, through the rubber grommet at the firewall passenger side to "run" the engine and transmission as the pins are already in the correct places in the pigtail.
The '89 interior harness should be the same as the '94 to communicate to the gauges and DLC

 

[someotherguy]

I think the trucks with 6.2's hat a TH400. But the pre 94 trucks with 6.5 had a standalone controller.

Yep, no idea here. 1991 was first year for 4L80E, dunno what the options were with diesels 6.2/6.5 and which combo with transmission. It'll be in the 1991 ordering info, for sure. If you believe whoever contributed that bit to wikipedia, in 1991 a 6.2 would come with a 4L80E, but I don't have any proof of it.

No, the 94 4l80 engine side harness will pull through from the ECM, through the rubber grommet at the firewall passenger side to "run" the engine and transmission as the pins are already in the correct places in the pigtail.
The '89 interior harness should be the same as the '94 to communicate to the gauges and DLC

Very little similarity in a 1989 and 1994 harness. The wiring would be pretty different between a 700R4 and a 4L80E to begin with, and additionally, the engine and transmission-related wiring which comes through on the passenger side of the firewall has a different shape to the block between 1990 and 1991. So there's going to be some modifications to be made, for sure. A simple direct swap of the harness between those years isn't going to happen, for more than one reason.

Richard

 

[wittensville]

Meh, the stock one works just fine and can be tuned and is on hand. Seems to me the engine harness and PCM ought to be swapped out. The added trans wiring should pass through the firewall on the passenger's side. There is no mention of 2wd 4wd on either the donor or the recipient. If those are different that throws a monkey wrench in the whole thing. How about wheelbases? The driveshaft length will be different between the 2.

They are virtually the same truck, extended cab long wheelbase the only difference is the 89 is the light 7200 lbs 3/4 ton with 6 lug wheels and 94 is a 3/4 ton with 8 lug wheels. Both are 4x4

 

[Erik the Awful]

I be following this as well. I have a 4L80 for Roscoe, but I still need to finish patching the frame for the engine mounts.

Has anyone mentioned a difference in transmission length? I suppose I ought to put my 4L80 and 700R4 side by side today and note differences.

From what I've read the stock internal harnesses weren't the best design nor highest quality. When they get old the tabs that hold them break, causing an ATF leak. The plug on my transmission wobbles, so I bought a new one. If you have the same problem, replace the harness while the transmission's out.

More Information for PIONEER 772038

 

[Nad_Yvalhosert]

Has anyone mentioned a difference in transmission length? I suppose I ought to put my 4L80 and 700R4 side by side today and note differences.

GM made up for the difference in the tranny length with the adaptor between the tranny and t-case.
I went from a:

manual tranny & NV241 to a
3L80 & NV241 to a
700R4 & a different NV241

in the same truck with the same front driveshaft and same rear driveshaft.

 

[618 Syndicate]

GM made up for the difference in the tranny length with the adaptor between the tranny and t-case.
I went from a:

manual tranny & NV241 to a
3L80 & NV241 to a
700R4 & a different NV241

in the same truck with the same front driveshaft and same rear driveshaft.

That's possible because there's only about a half inch difference in length and between a TH400 and a 700R4.
A 4L80 is 3 inches longer.

 

[tayto]

I think the standalone gm 4l80e pcm has no input for a MAP sensor being from a diesel. while it will still work i think some drivability/tunability will be lost. tuning is possible but limited as support community has probably been gone for 10+ years. you would be better off using the 94/95 TBI PCM IMO....

 

[Supercharged111]

I think the standalone gm 4l80e pcm has no input for a MAP sensor being from a diesel. while it will still work i think some drivability/tunability will be lost. tuning is possible but limited as support community has probably been gone for 10+ years. you would be better off using the 94/95 TBI PCM IMO....

You should only need TPS and RPM to control the trans.

 

[someotherguy]

You should only need TPS and RPM to control the trans.

Is MAP input not considered for downshift behavior (and possibly TCC lockup?) Curious, have no experience here, just wondering if that's why tayto mentioned it.

Richard