another 4l60 to 4l80e conversion

[lummy]

I have a 96 tahoe 4wd and the 60 looks to be shot.
I've been going back and forth on whether to get a rebuilt or do the conversion. Long story short, I picked up a 98 4l80e that was rebuilt about 10k ago. Marking on the tranny said it was rebuilt about 9 months ago and upgrades performed.The guy also threw in the tc, tc cover, transfer case, rear driveshaft and flywheel for $700 out the door. It does look like the transfer case is an np246 tho.

Right now, I'm trying to make sure I have everything I need and could use a sanity check so I have everything on hand when I start.

Got the trans, check.

input shaft. It looks like the 246 would be a PITA to wire up so I'd like to keep the 243 that's in there now instead. It looks like the 32 spline input shaft is the same part # for both the 246 and 243 so theoritacally, I should be able to swap the two. does this sound right?

transfer case adaptor. I'm guessing I can reuse the one that came with the 246, they look to be identical.

TC cover, I have the one that came from the 454 and should be good there. I need to confirm the bolt holes are in the same place as on the 60e.

wiring. I think I'm going to rewire the 60e harness and add the second VSS connector. I read a few places that the conversion adaptor was needed to allow the harness to reach since the 80 connector is on the opposite side. Is this a problem?

flywheel. Do I need to switch flywheels or can I use what is there now although I would only use 3 bolts? I didn't get the spacer from the 454 flywheel so if I do switch, I'm assuming I need to buy the spacer?

Tune. I got a quote from pcmforless for $175 for a retune. I'm not sure if there's anyplace local to SF Bay Area that can do it or a less expensive method, but I'm all ears.

tranny lines. I'll porbably pick up the sonnax kit.


driveshafts. I haven't measured the DS I picked up. the The donor was a 98 tahoe 2500 4 door so it should be close. I would have to replace the ujoint on the rear.
Front DS, am I better off scouring the junkyards or getting my existing lengthened?

What else am I missing?

 

[lummy]

any one?

 

[quietfly]

check out this link http://www.ls1truck.com/forums/front-page-news/14163-how-4l60e-4l80e-trans-swap.html

it should help with a sanity check. good luck!!!!

 

[lummy]

Yeah, I've read that one. The only problem is that it's for a NBS and a 6.0 ls1 so the flywheel definitely has to be changed. I haven't been able to find anything definitive about the flywheel for the OBS 5.7l.

Also, the mount is part of the frame whereas the OBS you can supposedly move the mount back and drill new holes.

 

[95TwinTT]

You will need the dip stick and tube for the 80. The output shaft on the 80 is larger than the 60, so if you don’t use the 80 transfer case, you might be able to swap the chain and sprockets to the 60 transfer case. I used the 60 xfer case and swapped out the shaft and sprocket.

The wiring differences are the speed sensors. The 80 has input speed as well as output speed. I had to swap a wire to the controller because of a pinout change between the two systems. I’m not using the stock ECU, but search for the specific wiring change to be made and it should show up.

I’m only using the rear speed sensor, since I don’t care what the input speed is. The rear one provides the same info the speed sensor did on the 60, speedometer, shift points, etc.

The rear mount cross member needs to slide to the next set of holes in the frame. Should be no need to drill holes. The front drive shaft needs to be replaced, as they can’t lengthen them. Shortening is easy, going the other way, not so much.

Bell housing bolt pattern’s the same, but older 80 tranny’s did not have the top hole in the housing.

Cooling lines can be gently bent around to reach the 80.

Good luck………….

 

[lummy]

Thanks for the input. Yeah, I have the dipstick, the guy I bought it from was just throwing everything in that I needed.

Did you use a stock convertor and what was the stall speed?

 

[95TwinTT]

The torque converter I started with was MPC (Midwest Performance Converters) 3200 stall, with multi disc lockup. Last summer, Midwest adjusted it up to 4200 rpm’s.

 

[lummy]

how is the 3200 stall TC? After a bunch of research, it looks like the stock TC from the 454 I have is a low stall 1400-1800. I have a feeling I'm going to want at least a 2200-2800 behind the L31 instead.

 

[95TwinTT]

I could not tell the 3200 stall from stock. Even now that it is 4200, it still drives like a stock converter in everyday driving. As long as you get the lockup version of whatever stall speed converter.

The higher the stall, the more torque it delivers……………

 

[lummy]

I could not tell the 3200 stall from stock. Even now that it is 4200, it still drives like a stock converter in everyday driving. As long as you get the lockup version of whatever stall speed converter.

The higher the stall, the more torque it delivers……………

Yeah, but full lockup at 1400 plus the fact that the gearing is lower the the 60e makes me scared that it'll be a dog from a dead stop.

I found a dual stator TC from autozone that's supposed to be stock for a 5.7l with an 80e behind it for $150. I'll have to call to double check the stall speed but I think it would be a better fit for me.