1979 K10 Silverado Overhaul & Modernization

[Bdsankey]

I figured I'd create a thread to track progress on a project my father and I are finally finishing up. My father has had a 1979 K10 Silverado that has been in a state of "mid restoration" for the last 15-18 years that's finally going back together. Before this restoration, he had used it as a daily driver and even plowed snow with it for years in the Upper Peninsula of Michigan, which is known for heavy salt use in the winters. I'll say plowing with a GM ZZ502 BBC made for some fun times as a kid! I would add some pictures, but the newest picture I have is from 2015. I'll get some as it's finishing up it's stay in our body shop before some final assembly.

Planned upgrades are to go to EFI, switch out the TH400 for a 4L80E, as well as update the gauges to a Dakota Digital setup. The biggest things we haven't tackled yet are how to get the individual fuel pumps to kick on when we switch tanks via the selector switch (might have to jump to the 87+ style selector, haven't figured out the wiring on it yet), and exactly what needs to be done to overhaul the transmission AND mate it up to the NP205 he already has. The truck still has a 12 bolt rear and a 10 bolt front with 3.73 gears and Auburn limited slip carriers in each axle. We're also running 35" tires as well on ProComp bullet wheels (16x8).

We are going to likely update the radio equipment as well as the AC (it's a factory air truck) but that will be handled once it runs and drives by itself as those changes are pretty easy to accomplish. The heavy lifting is going to be the dash/EFI wiring and plumbing to keep the truck looking factory.



Planned Update/Modernization Parts:
1) Holley Terminator X Max with transmission control (4x 100 lb/hr injector TBI version, 550-1011)
2) Holley HyperSpark BBC distributor
3) Holley HyperSpark CDI box
4) Holley HyperSpark coil
5) EFI System Pro Terminator>HyperSpark harness with tack output wire added
6) Holley in-tank pump modules for each tank (12-308)
7) Dakota Digital RTX Dash
8) Dakota Digital cruise kit for electronic speed
9) Dakota Digital gear shift indicator kit
10) Dakota Digital Holley BIM interface module
11) Dakota Digital temperature input module
12) MSD build your own wire kit and R&M wire holders to clean things up
13) Mishimoto aluminum BBC radiator (clearance sale)
14) Mishimoto aluminum dual fan shroud (clearance sale)

 

[PureHybrid]

Keep us posted on the Tcase deal, an acquaintance of mine is putting an 8.1/4L80 into a square Chevy and he's trying to find a path on what transfer case to use. The guy he bought the drivetrain from said to just flip the stock Tcase and run it upside down LOL

 

[Leadfoot]

Mating an NP205 that was bolted to a TH400 onto a 4L80E should be straight forward as both transmissions were 32 spline. The issue is the adapter for a 4L80E is hard to find and/or expensive. The factory only ran that combo a few short years and only in K30's, so finding a factory adaptor is tough. Advanced adapter I believe makes one and some other places (https://www.northwestfab.com/4l80E-to-TH400-NP205-AdapterSpacer-Kit_p_3452.html) sell spacers if you are just replacing a TH400 with a 4L80E. The site will tell you what transmission outputs you need as well. Depending on lift and current spline engagement, you may have to shorten the rear driveshaft (most driveline shops can do fairly cheap) and lengthen the front one (not as cheap). Keep an eye on that 12 bolt, I blew up two of them in my 78 K10 with a stock 350 on 33's.

 

[Bdsankey]

Keep us posted on the Tcase deal, an acquaintance of mine is putting an 8.1/4L80 into a square Chevy and he's trying to find a path on what transfer case to use. The guy he bought the drivetrain from said to just flip the stock Tcase and run it upside down LOL

I believe all I need to do is get a NP205 (according to @THEFERMANATOR ) out of a newer truck and put the tone wheel in the trans while it’s apart as it’s a press on ring for not a ton of cash. The only thing I don’t know is if the newer 205 is passenger drop to work with the axle in the truck.

 

[Bdsankey]

Mating an NP205 that was bolted to a TH400 onto a 4L80E should be straight forward as both transmissions were 32 spline. The issue is the adapter for a 4L80E is hard to find and/or expensive. The factory only ran that combo a few short years and only in K30's, so finding a factory adaptor is tough. Advanced adapter I believe makes one and some other places (https://www.northwestfab.com/4l80E-to-TH400-NP205-AdapterSpacer-Kit_p_3452.html) sell spacers if you are just replacing a TH400 with a 4L80E. The site will tell you what transmission outputs you need as well. Depending on lift and current spline engagement, you may have to shorten the rear driveshaft (most driveline shops can do fairly cheap) and lengthen the front one (not as cheap). Keep an eye on that 12 bolt, I blew up two of them in my 78 K10 with a stock 350 on 33's.

Man I don’t know how we haven’t killed it yet but he’s plowed with it for a decade as well as done hundreds of burnouts and truck pulls. It just keeps ticking.

 

[Leadfoot]

Keep us posted on the Tcase deal, an acquaintance of mine is putting an 8.1/4L80 into a square Chevy and he's trying to find a path on what transfer case to use. The guy he bought the drivetrain from said to just flip the stock Tcase and run it upside down LOL

Not a good idea to run those tcases upside down due to the pumps they run. That said, while not cheap, getting an NP205 to bolt behind that 4L80E is a "bolt in" affair (90-91 Crew Cabs automatics ran that combo). The adapter is the biggest cost and there are a few companies that can machine the NP205 tailhousing to accept a VSS.

 

[Bdsankey]

Not a good idea to run those tcases upside down due to the pumps they run. That said, while not cheap, getting an NP205 to bolt behind that 4L80E is a "bolt in" affair (90-91 Crew Cabs automatics ran that combo). The adapter is the biggest cost and there are a few companies that can machine the NP205 tailhousing to accept a VSS.

VSS isn’t an issue nor is making driveshafts. VSS will be handled by the tone ring I’ll add to the rear planet inside the 4l80.

What I want to do is mate it to the 4l80 in the most effective way possible.

 

[Leadfoot]

I believe all I need to do is get a NP205 (according to @THEFERMANATOR ) out of a newer truck and put the tone wheel in the trans while it’s apart as it’s a press on ring for not a ton of cash. The only thing I don’t know is if the newer 205 is passenger drop to work with the axle in the truck.

That will work, but will show incorrect speed in low range (and may affect shifting). If it's a GM/Dodge NP205 they were all passenger side drop. Ford NP205's were driver's side drop. A few guys who SAS swapped Duramax trucks have either run a Ford front axle (which has a driver's side pumpkin) or adapted a GM case to run a GM/Dodge solid axle.

 

[Bdsankey]

That will work, but will show incorrect speed in low range (and may affect shifting). If it's a GM/Dodge NP205 they were all passenger side drop. Ford NP205's were driver's side drop. A few guys who SAS swapped Duramax trucks have either run a Ford front axle (which has a driver's side pumpkin) or adapted a GM case to run a GM/Dodge solid axle.

I’m not worried about incorrect VSS in low as I believe I can tell the Holley it’s in 4lo.

 

[Leadfoot]

VSS isn’t an issue nor is making driveshafts. VSS will be handled by the tone ring I’ll add to the rear planet inside the 4l80.

What I want to do is mate it to the 4l80 in the most effective way possible.

From the research I have done, if the truck already has full NP205/TH400 setup with factory adapter, then the spacer is the easiest route as long as there is enough spline on the 4L80E output. Worst case scenario is an output shaft swap (requiring a full trans teardown). Pulling the signal off the trans may be an issue with low range operation depending on what you are using for a trans controller and speedometer readout.

Edit: Just saw your response about being able to adjust using the Holley EFI.

 

[Bdsankey]

From the research I have done, if the truck already has full NP205/TH400 setup with factory adapter, then the spacer is the easiest route as long as there is enough spline on the 4L80E output. Worst case scenario is an output shaft swap (requiring a full trans teardown). Pulling the signal off the trans may be an issue with low range operation depending on what you are using for a trans controller and speedometer readout.

Edit: Just saw your response about being able to adjust using the Holley EFI.

So quick Google search says the Holley will accept the input but doesn’t have a way to multiply/divide speed.


I’ll ask my pops what combo exactly was in the truck. It looks like having a 205 machined may actually be the smarter route. I’ll play around in the Holley software and see how shift tables are mapped.



Edit: Actually leaving it in the trans will keep all parameters the same on shift strategy. I would just use an input to turn off converter lock in 4lo since the output shaft speed will be the same. The only downside is VSS will be off on the speedo but that isn’t an issue.

 

[JoshH]

If the trans controller doesn't know its in low range and gets the output speed from the trans (pre-transfer case), nothing will change. It'll shift exactly the same as it does in high range because all the gearing change takes place after the sensor.

 

[Bdsankey]

If the trans controller doesn't know its in low range and gets the output speed from the trans (pre-transfer case), nothing will change. It'll shift exactly the same as it does in high range because all the gearing change takes place after the sensor.

Which should be fine other than the speedo will not reflect the proper value but that isn't an issue. If it really becomes an issue I will put a GPS speedo in it but I'd rather not, especially when 4lo will not be used very often if ever.