K20 LV3 TR6060 NP241

[EcoK20]

So I thought I'd share some of what I'm working on since it's got a lot of things that I haven't seen all put into one package and figured someone might find useful information in what I'm doing. I've been planning this project for some time, and recently felt like I had enough parts and was healthy enough to start. I'm working with a low mile 1980 K20 that started life with a 292, SM465 and an NP205. I picked it up at an auction in rural OK for what I felt like was a good deal. I got it running and drove it for a while but didn't feel like it was very user friendly. I wanted something with better mpg, an overdrive, and overall better for modern driving. I had a low mile LV3 from a 2014 silverado left over from another project that was nixed. I thought that would make a great engine for what I'm hoping is a good daily driver. I debated transmissions for a while and decided I wanted a TR6060. The unit I'm using is from a 2010 camaro. After having removed an np203, I did not want to have to work on a 205 with their weight. I know they are bulletproof, but way overkill for what I'm wanting. I found an np241 passenger drop transfer case to use. To mate the gen V engine to the TR6060 requires an 8 bolt flywheel. A manual was never optioned behind a gen V in the truck application, BUT the LSA uses an 8 bolt crank. I picked up a dual mass clutch and flywheel on ebay and bolted it on. Gen V engines require a 3/8" bell housing spacer because the cranks aren't bored deep enough for the snout of the 6060 (maybe other manuals as well). To mate the tr6060 to an np241 requires some work. The options I was able to find were cost prohibitive, so I made my own adapter. This requires the transmission to be completely disassembled, a corvette output shaft to be installed and a corvette tailhousing to replace the 2wd camaro housing. Then you have a flange to bolt to. I had a plate cut and machined to fit, and a "snout" to bolt to the plate that also has a bolt pattern to bolt the cast iron transfercase mid-mount thing to. note: if you two-bolt the top two bolt holes on the tailhousing, you will need to clock the transfer case pattern approximately 9* to be "level". I'm using Tejas engine mounts and still needed to clearance my v8 crossmember for the oil pan. I'm at the point of drilling out my frame to move the trans crossmember back. Truck shown on a scale at 5060lbs. More updates to come

 

[EcoK20]

Here are the weights of the old and new units. Not as much savings as I was hoping

 

[EcoK20]

Engine cross member clearance

 

[EcoK20]

I have an '88 R30 that I used for reference when installing the oem hydraulic clutch pedals and the old MC from that truck to use for mock up. Here are pics of the MC placement. The rest of the pedal assembly is like it was so no useful pics of that

 

[bucket]

I believe you are in uncharted territory with that tr6060 4x4 swap. That's a very tall 6th gear isn't it? What is the axle gearing going to be?

 

[bucket]

Oh yeah, and howdy from Ohio! I moved this thread to the tech section since it's loaded with it, lol.

 

[EcoK20]

Thanks for moving it. I hadn't figured that out. I can get pretty granular with this is people want to know more. Here is how I figured the rear end gear. I'll probably go with a 3.73

 

[Grit dog]

Thanks for moving it. I hadn't figured that out. I can get pretty granular with this is people want to know more. Here is how I figured the rear end gear. I'll probably go with a 3.73

With that deep of an OD even with the small tires I’d go 4.10s at least. Otherwise 6th gear will be virtually useless unless you’re going 20 over the speed limit on flat roads. And even then it will only be barely useable.

And after all that work you’ll just end up with the exact opposite issue that most of us have with 1 to 1 top gears.

 

[bucket]

What are your plans for 6th gear usage? 3.73 should be fine if you only plan on 6th being your steady cruise highway gear. But for using it at any other time, you will probably find it much more useful with a 4.10 or even 4.56 gear. I say this because my buddy had a '14 V6 Silverado for a while, it seemed like it was often downshifting from 6th and that need will be amplified by a manual transmission.

Also, it's more of an apples to oranges comparison and I haven't done the gearing/rpm math on it, but I have a '13 Savana with 4.8L, 6L80e (maybe 6L90? I can't remember) with a 3.23:1 rear, which has 265/70's on it now. 6th gear is ONLY used for steady cruising with no load. Loaded down with the entire family, any hill or headwind traveling at 65-75 mph has it constantly hunting between 5th and 6th. I often just lock it out of 6th on those occasions. Anyway, that van is probably more of a brick-in-the-wind like an old squarebody truck.

 

[bucket]

With that deep of an OD even with the small tires I’d go 4.10s at least. Otherwise 6th gear will be virtually useless unless you’re going 20 over the speed limit on flat roads. And even then it will only be barely useable.

And after all that work you’ll just end up with the exact opposite issue that most of us have with 1 to 1 top gears.

Looks like you beat me to it. We are thinking the very same thing.

 

[EcoK20]

My main goal at this point is to get it going. I expect to change rear gears more than once, just because that's how things seem to work around here. Once I get the rear where the gearing is happy, I'll change out the front to match. Good thing is there are options. After the mechanicals get lined out, it'll get tore down for prettfying. I spent years in a geo metro, so I plan on some "aero" additions to help with wind resistance, though I doubt they'll be much help on a "square" body.

 

[AuroraGirl]

Engine cross member clearance

did you use v8 engine pads when you went from i6 to v8? And what transfer case crossmember you using? I have a np208 on a 1986-1987 w cross member, but i have a sm465 (not sure if your custom engine and trans make the length a wild card or not)
I ask because an np205 crossmmember from 1980 is not going to be the same height likely as where a 241/208 would be sitting.

 

[AuroraGirl]

My main goal at this point is to get it going. I expect to change rear gears more than once, just because that's how things seem to work around here. Once I get the rear where the gearing is happy, I'll change out the front to match. Good thing is there are options. After the mechanicals get lined out, it'll get tore down for prettfying. I spent years in a geo metro, so I plan on some "aero" additions to help with wind resistance, though I doubt they'll be much help on a "square" body.

you plan to not at all use your 4wd to dial in the rear to your liking?

 

[EcoK20]

did you use v8 engine pads when you went from i6 to v8? And what transfer case crossmember you using? I have a np208 on a 1986-1987 w cross member, but i have a sm465 (not sure if your custom engine and trans make the length a wild card or not)
I ask because an np205 crossmmember from 1980 is not going to be the same height likely as where a 241/208 would be sitting.

Yes, I used the cross member and pads from a 4wd suburban, late 80's from a pull-a-part yard. I'm using the trans cross member that was on the truck. It's they type that only bolts to the bottom of the frame rails, unlike some that have the extra supports that reach up to the top of the frame as well. My first mock up had the cross member so far back that it was into the part of the frame where it begins to bend up for the bed, so I had to mill my "snout" shorter and remove 1" from the output shaft. I tried lifting the engine/trans assembly to match the rear u-joint angle and ran into more clearance issues, so it came back out. Waiting for a couple days with no rain to mock it back in there. A spacer will be needed under the transfer case mount to get the right driveshaft angle. The Tejas mounts raise the engine up and forward.

 

[EcoK20]

you plan to not at all use your 4wd to dial in the rear to your liking?

As the gearing is now, I'll try the 4wd, but once I start swapping rear gearing, I'll probably leave it in 2wd so I'm not spending trial and error money on two axles. I'm not planning on using the 4wd much anyway, mostly for the muddy lease roads/fields and snow