Kicking around doing an LS swap

[R Carnella]

Or was that switch specifically to tell the computer you were in low gear?

Yes it for the ecm so trans will shift in low range, also indicate on dash just cause i can.
The speedo and other info is serial data from the ecm.

 

[Bextreme04]

LS ECM's have different hi and low range tables for shifting, engine braking, and some other things. You need the 4lo switch to tell it when to change tables on SOME of them. I can't remember exactly which ones, but I know that my 0411 ECU on the 454/4L80e needs it or it won't act right in 4lo.

 

[SquareRoot]

I forgot about the ECU controlled trans you guys are running. I went from a Turbo 400 to a NV4500. No computers on my truck except for the stand alone Edelbrock PF-4.

 

[mcarlo86]

My last tank got me 9.5 mpg. And I've been driving like a grandpa (sorry to all the grandpa's out there). I'm not looking to win any contests, but I'm hoping for 12 - 14 mpg. I knew mileage was going to be an issue when I bought the truck, but at one point it was down to under 6. I want better mileage mostly for convenience so I can go farther than 100 miles on a tank.

I've been working my way through the "other problems" and resolved a really rich condition and a few other carb related issues. I have not popped the Quadrajet off to look for leaking well plugs yet. That is on my to do list along with checking that the 700r4 is shifting into OD correctly (I think I am going to have to rig up a test light at the solenoid). I haven't done a leak/smoke test to look for vacuum leaks but have sprayed starting fluid all over the place with no changes and I haven't checked compression.

The LS swap is either going to be the last resort or if I come across a windfall. Right now, I am asking myself (and you guys) what I would need if I were going to do this so I can lay everything out to SWMBO for project approval.

We had an '83 K20, 350, Quadrajet, SM465 4 speed, 3.42 gears, and 31" tires that used to get 14-15 mpg. I think you should get that carb rebuilt and check for fuel leaks. What shape is the distributor in? Plugs/wires? How is your timing set? Vacuum leaks?

 

[Bruce Wingate]

Carb rebuild is in the near future before I drop money on a new engine. Plugs, wires, distributor and coil(? HEI distributor) are new.

I haven't been able to identify any vacuum leaks but I haven't tried too hard either - spraying carb clean or starting fluid around the carb didn't cause any changes. I'm debating doing a smoke test to see what happens.

I don't think I have a fuel leak. All my connections in the engine bay look dry (haven't checked under the carb for well plug leaks yet.)

I'm embarrassed to say this - but I have been unable to see the timing mark every time I tried. I had a trusted shop time the engine. I think they set is at 4 degrees BTDC. Previously, I hooked a vacuum gauge up a while ago and I'm pulling 20 inches (PSI? I'm not sure of the units.) I think the gauge was bouncing a little when I checked I'll have to double check this and see what is happening and what it could mean.

 

[Skyfall]

Hello All:

Thanks for all of the useful information! In lieu of starting a new thread, I decided to ask a question here because I believe that you all have the answers.

I have a 1991 R3500 that I have converted to a 4x4 (minus the part that actually makes it a 4x4...the transfer case...haha). It has a TBI 350 with 84K miles.

Based on what I read here, my factory 4L60e has a 27 spline output shaft. In order to keep the VSS and connect it to a 27 spline NP205, I need to use the Advance Adapters "4L60E HEX PATTERN/4L60E SHAFT 50-0405E" <--link

I believe that I will also have to swap the "long" 2wd output shaft for a "shorter" 4x4 shaft (I watched a YT video where a guy cut the shaft off, but that is probably not the best idea).

I will add the microswitch for 4-low per the information in this thread.

Besides shortening my rear driveshaft and purchasing a stock front driveshaft, am I missing anything?

I want to make sure that I am buying the correct parts as they are quite expensive.

Regards,

 

[Camar068]

Hello All:

Thanks for all of the useful information! In lieu of starting a new thread, I decided to ask a question here because I believe that you all have the answers.

I have a 1991 R3500 that I have converted to a 4x4 (minus the part that actually makes it a 4x4...the transfer case...haha). It has a TBI 350 with 84K miles.

Based on what I read here, my factory 4L60e has a 27 spline output shaft. In order to keep the VSS and connect it to a 27 spline NP205, I need to use the Advance Adapters "4L60E HEX PATTERN/4L60E SHAFT 50-0405E" <--link

I believe that I will also have to swap the "long" 2wd output shaft for a "shorter" 4x4 shaft (I watched a YT video where a guy cut the shaft off, but that is probably not the best idea).

I will add the microswitch for 4-low per the information in this thread.

Besides shortening my rear driveshaft and purchasing a stock front driveshaft, am I missing anything?

I want to make sure that I am buying the correct parts as they are quite expensive.

Regards,

when you go to get your engine, get the transmission (4x4) with it. Then take your old stuff and sell it for funds for the NP205 adapter kit you need. Keep in mind that NP205's have a figure 8 bolt pattern and the circle pattern.

I'd start another thread for your build and ask questions from there. Search......ask......search....ask.....share your findings.....search....ask.....so on and so forth.

And of course, we like pics!!! Future advice, do your first harness yourself so you know it inside and out for troubleshooting later.....and lastly.....check all the grounds from the ECM to battery before attempting to fire....saves headaches and double work later on. Only takes about 10 minutes with an ohm meter.

Have fun and good luck

 

[Skyfall]

I am not planning in removing my engine. I just want to know if the parts I mentioned are compatible for my build. The truck is mostly finished with the exception of the transfer case. Will my 4L60e work with a 27 spline NP205 with the Advance Adapter unit between them (with the VCC)? If so, then I am going to go ahead and purchase the parts I found so I can get this truck on the road. Thank you in advance.

Regards,

 

[Bextreme04]

I am not planning in removing my engine. I just want to know if the parts I mentioned are compatible for my build. The truck is mostly finished with the exception of the transfer case. Will my 4L60e work with a 27 spline NP205 with the Advance Adapter unit between them (with the VCC)? If so, then I am going to go ahead and purchase the parts I found so I can get this truck on the road. Thank you in advance.

Regards,

A 91 3500 would have had a 4L80e from the factory, not a 4L60. What NP205 are you looking at? Is it a figure 8 or a circle pattern?

 

[Skyfall]

Thanks for pointing that out. You are correct. The NP 205 is a figure 8 pattern. I have done some further research and found someone to speak with about this. I believe I have the solution that I am looking for. I should create a build thread for my truck to help other people who are doing the same / similar project.