The mythical CUCV 4L80E swap

How is the remote sensor setup

Second to last pic on the first post. It's pretty much just a cable that's hooked up on the injection pump and the cable routes to the remote sensor. It's nice cause there are a bunch of holes to fine tune the length of pull and how much it actuates the sensor.

Great write up. I have the trans, I think I found a good builder yesterday from a recommendation. And I hope to start in Feb. The few tools needed to rebuild them yourself are big bucks. It's not worth buying them to sit around afterwards. Or wondering if you did it correctly. I am running the 205 transfer case. I did find an adapter from NW fab works to bolt on for the transfer case adapter to bolt up. I have to change the output shaft to a shorter one with full splines and it also has the encoder wheel on it for the speed sensor, and I bought the fully splined shaft on epay. The trans I have is a 2 wheel version. I can cut the replacement shaft to length or do the adapter machining which would eliminate the NW fab works adapter and then cut it to fit. I am still undecided on the controller. I still have some homework to do. LMC has the correct shift indicator for the steering column. This thread will be a great help when the time comes. Thanks for the posting and especially the long term follow up.

Thanks. You'll definitely be happy with the improvement that extra gear makes.

It's been a little over 5 years now and just under 30k miles. I've done a ton of off road driving, mud, sand and rocks. I've towed other cars, and even dragged a destroyed full size pickup with 2 flat tires about 11 miles down a dirt road so it could get onto a flatbed tow truck. I'm very happy with choosing the heavy duty 4L80 over the 700R4 that a lot of people suggest.

I picked up a 98 2wd 4l80e for $110 on Friday. That being said I will have to convert it to a 4wd setup. I'm gonna go through the transmission myself as I own/operate a shop so I'm thinking I may make a "brief" thread on going through the 4l80e. If that would have any appeal to anyone and/or hasn't already been done. Obviously one can just acquire a tear down manual pretty cheap so it's not exactly nessecary.

brazengoat06 said:

I picked up a 98 2wd 4l80e for $110 on Friday. That being said I will have to convert it to a 4wd setup. I'm gonna go through the transmission myself as I own/operate a shop so I'm thinking I may make a "brief" thread on going through the 4l80e. If that would have any appeal to anyone and/or hasn't already been done. Obviously one can just acquire a tear down manual pretty cheap so it's not exactly nessecary.

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Nice. Just be sure you post some good pictures! Ha ha

brazengoat06 said:

I picked up a 98 2wd 4l80e for $110 on Friday. That being said I will have to convert it to a 4wd setup. I'm gonna go through the transmission myself as I own/operate a shop so I'm thinking I may make a "brief" thread on going through the 4l80e. If that would have any appeal to anyone and/or hasn't already been done. Obviously one can just acquire a tear down manual pretty cheap so it's not exactly nessecary.

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The only problem is all the special tools needed. I spent over $500.00 for all my 4L80E tools. If I was going to do this I would go with the 6L90E . Though all the special tools cost me over $2000.00 so the average guy should just take it to a transmission shop to get it rebuilt.

rustystud said:

The only problem is all the special tools needed. I spent over $500.00 for all my 4L80E tools. If I was going to do this I would go with the 6L90E . Though all the special tools cost me over $2000.00 so the average guy should just take it to a transmission shop to get it rebuilt.

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The 6L90 would be awesome, but it would probably be a lot harder to find a used one. And probably more expensive too.

True Knight said:

The 6L90 would be awesome, but it would probably be a lot harder to find a used one. And probably more expensive too.

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I almost got one for $300.00 . It was out of a destroyed 2014 1 ton Chevy. The guy was parting it out and I got there too late !

True Knight said:

The 6L90 would be awesome, but it would probably be a lot harder to find a used one. And probably more expensive too.

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One item required, if using a NP205;

GM 4WD 6L90E 6 Speed Automatic Transmissions to GM NP205 Circular 6 Transfer case.
from Advance Adapter, $695.00

"GM's new Hydra-Matic 6L90 transmissions are the first of a new family of modular six-speed rear-drive transmissions. The transmissions feature two overdrive gears and a wide, 6.04:1 gear ratio spread to improve performance and fuel economy when compared with conventional four- and five-speed automatic transmissions. With two overdrive gears, engine rpm is reduced by approximately 9 percent at 60 mph - a reduction to about 1,500 rpm. Lower engine rpm can bolster fuel economy because less fuel is used. A lower-rpm cruising speed also enhances smoothness and reduces noise heard in the vehicle's cabin."

Nice, but this is going to be very expensive.

Regards

Joseph

Jozseph said:

One item required, if using a NP205;

GM 4WD 6L90E 6 Speed Automatic Transmissions to GM NP205 Circular 6 Transfer case.
from Advance Adapter, $695.00

"GM's new Hydra-Matic 6L90 transmissions are the first of a new family of modular six-speed rear-drive transmissions. The transmissions feature two overdrive gears and a wide, 6.04:1 gear ratio spread to improve performance and fuel economy when compared with conventional four- and five-speed automatic transmissions. With two overdrive gears, engine rpm is reduced by approximately 9 percent at 60 mph - a reduction to about 1,500 rpm. Lower engine rpm can bolster fuel economy because less fuel is used. A lower-rpm cruising speed also enhances smoothness and reduces noise heard in the vehicle's cabin."

Nice, but this is going to be very expensive.

Regards

Joseph

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If you get one out of a 4X4 truck you will not need that adapter.

Then again, with the limited power, the 4L80 is probably all the truck needs. With the 6L90 you'd probably need to lower the axle gearing just to make the 6th gear usable. Ha ha.

rustystud said:

If you get one out of a 4X4 truck you will not need that adapter.

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FWIW;

"This kit fits GM NP205 circular pattern 32 spline input transfer cases. This kit will replace the 32 spline input with a new 29 spline input to match the 6L90 29 spline output shaft. The transfer case will require some disassembly of the front input to install the new gear assembly."

The above is from the installation instructions.

Regards

Joseph

Okay guys let keep this as a 4L80 thread. We can start a 6L90 thread if needed.

i need some helpful info. apparently there are two different length output shafts to choose from for those of us converting 2wd 4l80's. Can anyone tell me if i need the 3 3/4" or the 5" long output shaft to go with the NP205? Thanks

Also to comment on the special tools, I haven't spent anything on special tools to disassemble the transmission.

I am doing the exact same conversion you are Brazengoat06. I purchased a fully splined output shaft on epay. This shaft has the encoder wheel on it for the speed sensor. I need to measure the engagement needed and trim this shaft back and have it installed when the trans gets rebuilt. Now I purchased a small circular adapter from NW fab works that eliminates the need to machine the trans and transfer case adapter. So I can go either route on this before cutting the output shaft back some. I just sadly sold my M35A2 so the funds are there to speed this project up some. I also elected after a lot of reading on another forum to not do my own rebuild. I saw lots of expensive tools to rebuild them. A post I found elsewhere from Jake at Jakes transmission (they specialize in the 4L80E) that you could get by without most tools. But he mentioned two you need for reassembly. Seal installers and something else. They were expensive. The info is on a dead laptop and I don't know if I could find it again. If you do your own rebuild, hopefully you can get by OK without them.
I am going to have mine done. I wish I had the time to do my own. I don't... Post up how it goes.

brazengoat06 said:

i need some helpful info. apparently there are two different length output shafts to choose from for those of us converting 2wd 4l80's. Can anyone tell me if i need the 3 3/4" or the 5" long output shaft to go with the NP205? Thanks

Also to comment on the special tools, I haven't spent anything on special tools to disassemble the transmission.

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You will need special tools to assemble it though. Or you run the risk of damaging seals and the Teflon rings.

Actually you can use a feeler guage and another tool that you can make for about $1

Since no one has the exact specs for the output shaft and 4wd adapter I am kinda halfway shooting in the dark. But what I decided to go with to see if it matches the np208 is the 2 5/8 adapter and the 3 3/4 output shaft. I should have the rest of the transmission back together tomorrow and the transfer case out of the truck for testing shortly after. That way future "conversionist" will have the parts specs.

brazengoat06 said:

Actually you can use a feeler guage and another tool that you can make for about $1

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You can do that and run the risk of a damaged seal ring and not know until it is in the truck. Or you can buy the correct tool and do it right.