4L80E/NP205 swap

[bilfman]

Hi peeps,

I just completed a 4L80E/NP205 swap and am going to go through the build here in the forums. I looked on the net many times and couldn't find a 'real life' start to finish of a project like this. I replaced the TH400/NP203 in my 1979 crew dually.

The basics of my dually are it is a 454 with hooker headers, edelbrock performer, edelbrock 750cfm carb. Diffies are dana 60 up front and dana 70 in the rear. The 60 has a eaton tru-trac locker and the 70 has a detroit locker and I am running 3.73 gears. I was running about 2600 rpm at 60 mph.

In 1991 GM released a 4L80E/NP205 combo this was only available in the crew cabs, which were still square bodies in 1991. These are very hard to find, but I was able to locate one for a steal of $600.

I have done many resto in the past 30 years but the electronic transmission had me a little worried. For those of you who feel as I do, I can tell you now it is a piece of cake. As you follow the build you will see how simple it really is.

The trans and tcase looked rough under 21 years of grime, but to me it was a diamond ready to be worked. Here are some pics of the beast when it arrived.

[bilfman]

This is my little gem that will recieve the 4th gear gift....

[bilfman]

What initiated this whole deal was the NP203. These cases were designed to be full time 4wd. When converted to part time, as mine was, they had to be engaged to be oiled properly, this had to be done every 100 miles or so. Another fix to eliminate this is to extend the filler bung with an elbow and a 2" nipple, basically lets you fill the case with another 2" of oil. So my mind was thinking 205 the whole time and once I heard there was an NP205/4L80E combo the hunt was on........

[bilfman]

Break out the rags, sandblaster, chisels, hammer and a lot of 'pita' work and I have the trans and tcase cleaned up enough for putting in the truck. I resealed all covers and changed all the oil seals. Here are some shots of the process.

[bilfman]

The crossmember mount was siezed solid and the studs had to be ground off to be removed. I rebuilt it with a piece of 1/8 plate and a couple of new studs and it was good as new. It was a little tricky welding so as not to damage the rubber mount!

[bilfman]

Now that stuff was cleaned up and workable it was time to REALLY commit. I go from a truck that works just fine to putting in a trans and tcase the I'm not positive work and also enter the electronic transmission realm that is fully foreign to me.

Cleaning the parts up took over 10 hours of work, chip chip chip. The rust on the tcase and adapter had to be slowly chipped off with a small chisel and hammer.

[DirtyLarry]

That is cool! You will love that combo over a TH400/203 every day from here on out. Overdrive is always a good thing. Love the truck too!

Okay, the question begs to be answered….what is so special about a 1991 4L80E/205 vs. a 1985 or later 205 that would have been behind a TH400 mounted to a later 4L80E? The early 90's 4L80E’s had a horrible reputation for reliably but I doubt that 4L80E is the original 1991 piece anyway being most failed before they ever saw 100,000 miles. Is the 4L80E/205 adapter unique to 1991? Seems people have been hanging 205s on the back of 4L80E’s quite easily for years without searching for a rare 1991 specimen but I haven't followed exactly how they did it being I am not much of an automatic fan.

[Swed-Chevy]

Originally Posted by DirtyLarry

That is cool! You will love that combo over a TH400/203 every day from here on out. Overdrive is always a good thing. Love the truck too!

Okay, the question begs to be answered….what is so special about a 1991 4L80E/205 vs. a 1985 or later 205 that would have been behind a TH400 mounted to a later 4L80E? The early 90's 4L80E’s had a horrible reputation for reliably but I doubt that 4L80E is the original 1991 piece anyway being most failed before they ever saw 100,000 miles. Is the 4L80E/205 adapter unique to 1991? Seems people have been hanging 205s on the back of 4L80E’s quite easily for years without searching for a rare 1991 specimen but I haven't followed exactly how they did it being I am not much of an automatic fan.

Yes nice truck.My -92 Cheyenne with 4L80E have also failed and losing OD and lock up when the oil being warm.Have heard this is a common problem on the early 4L80E.Have also read that it could be an valve who are worn out in the valve body.

Have anyone here removed the valve body when tranny still in the car ? If there are steel balls or springs who can fell of.

http://67-72chevytrucks.com/vboard/s...27#post5413127

http://www.sonnax.com/system/announcement/34200-16K.pdf

[asphaltburner]

How cool, bilfman!
You've gone the step I probably should have when I went with the TH400/NP205 build in my truck (from TH400/NP203)! The truck is used frequently for heavy chores, but the electronics and overdrive would be nice, especially since my front and rear gears are 4.11:1.
As little as it hits the highway, I guess re-building what I had was a good way to go.
It sure turned out to be an outstanding truck with amazing capabilities!
Good luck with yours!
Todd.

[JCampbell]

Killer thread.

[cleansquare]

Thanks for the thread! I enjoyed all the info. I bought the TCI controller like you recommended but their version of the vable X is too spendy, Ill buy the cable X. Also Ill look up the acculink tps. Thanks!

[cleansquare]

I'm so glad this thread is here. Been looking at it quite a bit. I have a few questions.

1. So the TCI harness hooks to the speed sensor on the transmission, and the Cable X White wire (signal) goes to the TCI Harness? The instructions kinda say they both are hooked up to the speed sensor on the trans lol. But it makes sense that the tci computer reads the speed sensor and then has a special wire for the cable x. I think I have that right.

2. You mention that the negative side of the coil and such is not a clean enough signal, and you need to use the RPM Module supplied with the kit. You show the yellow wire going to the harness, black to ground and the white wire going to the 'HEI Tach" plug. Does this mean the tach terminal on my distributor? So basically, I CAN use the tach terminal on the distributor as long as I use the RPM module?

3. WHere did you connect your 12v Switched wire to?

Everything else looks pretty simple, I figured out by reading your thread I dont need the manual shift, Forced tcc lockup, performance mode or economy mode, and I wont need the electronic speedometer wire.

ANy info on the above Q's would be awesome.

Heres a pic of the harness hanging off the TCU, sorting out what I do and dont need.

[bilfman]

Originally Posted by cleansquare

I'm so glad this thread is here. Been looking at it quite a bit. I have a few questions.

1. So the TCI harness hooks to the speed sensor on the transmission, and the Cable X White wire (signal) goes to the TCI Harness? The instructions kinda say they both are hooked up to the speed sensor on the trans lol. But it makes sense that the tci computer reads the speed sensor and then has a special wire for the cable x. I think I have that right.

2. You mention that the negative side of the coil and such is not a clean enough signal, and you need to use the RPM Module supplied with the kit. You show the yellow wire going to the harness, black to ground and the white wire going to the 'HEI Tach" plug. Does this mean the tach terminal on my distributor? So basically, I CAN use the tach terminal on the distributor as long as I use the RPM module?

3. WHere did you connect your 12v Switched wire to?

Everything else looks pretty simple, I figured out by reading your thread I dont need the manual shift, Forced tcc lockup, performance mode or economy mode, and I wont need the electronic speedometer wire.

ANy info on the above Q's would be awesome.

Heres a pic of the harness hanging off the TCU, sorting out what I do and dont need.

1. I used the speed sensor wire off the tranny with the supplied TCI connector and then used the computer wire to feed the cable x. I just set the cable x dip switches exactly how it is in the TCI manual.

2. Yes you use the HEI tach lead with the module.

3. There are leads on my fuse panel that work as a 12v switched, I just used that.

Yeah there are plenty of wires that you dont need if you don't plan on using the options. Glad to see the thread helped. It was all foreign to me and I couldn't find a good build source. Happy to have helped shed some light.

Truck looks great, post some pics

[cleansquare]

Hey bilfman, there are two sensors on the drivers side of the 4L80e, the front one the input and the rear the output which is whhat Im told to use for the speed sensor.

WHat, if anything, goes in the input sensor plug? I have nothing on the tci tran harness I dont believe. Thanks if you can help.

[cleansquare]

Hey bro, you have any issues with how quicl you tci controller controls shifting in you ride? My 4l80e was fully rebuilt but it seems like it shifts early. Like 1st into 2nd at like 15 mph and into 4th by 35! Is that normal? The tci controller doesnt seem to have shift setting capabilities other than firmness and all that crap lol
Posted via Mobile Device

[bilfman]

Those two are not used with the TCI . If you play around with the shift firmness and shift aggressiveness you can have it shift just how you like it. Hope that helps
Posted via Mobile Device and yeah it shifts through the gears pretty quick at light throttle.
Speedo is not one of those two , should be on the tailshaft.

[Duck1]

Originally Posted by bilfman

Those two are not used with the TCI . If you play around with the shift firmness and shift aggressiveness you can have it shift just how you like it. Hope that helps
Posted via Mobile Device and yeah it shifts through the gears pretty quick at light throttle.
Speedo is not one of those two , should be on the tailshaft.

4WD units only have the front sensor

[hick]

THANK YOU FOR THIS

I am spending more money then I had planned... but WELL worth it...

[DirtyLarry]

Bilfman,

How you liking that TCI EZ ECU after using it for this long? Thinking of the TCI EZ TCU for another project I am working on. Looking for feedback on how it does long term.

Thanks

[bilfman]

Originally Posted by DirtyLarry

Bilfman,

How you liking that TCI EZ ECU after using it for this long? Thinking of the TCI EZ TCU for another project I am working on. Looking for feedback on how it does long term.

Thanks

Hi dirty,

The TCI unit has performed flawlessly since install. I do not have a bad thing to say about it. Runs everything fine even in our - 40 winters. I love the handheld with it too. I got an old 46 Power Wagon this past summer from Wyoming it was HOT 95-100 degrees. I picked it up with the old dually and it trailered that 6600lb beast no problem. It was great to use the handheld to monitor the trans temp when pulling in the hills with that heat. I would buy it again in a heart beat. Works great and simple to install. 100 times easier then your 8.1 conversion.

[DirtyLarry]

Good to know as I’m the proud new owner of a TCI EZ-ECU kit. It’s going into THIS quazi-454SS clone I put together for my father in-law. Now the search is on for a 4L60E or 4L80E. We’ll see which pops up first for the right price. The truck is just a little 2wd ½ ton short bed stepside so I am not real worried about using a 4L60E in this truck if I can’t find an 80E for the right price. My FIL is getting to the age where the 5 speed is getting tougher for him to drive. He already smoked the new clutch I installed in it a few thousand miles ago. I guess you could say he is still getting used to driving the truck with a 7.4L instead of the gutless 4.3L. Time for a slushbox auto!

Thanks for the feedback

[Rogier]

Originally Posted by DirtyLarry

Bilfman,

How you liking that TCI EZ ECU after using it for this long? Thinking of the TCI EZ TCU for another project I am working on. Looking for feedback on how it does long term.

Thanks

Two different TZI units broke down on me in two different cars, the easy config settings went all off the chart and the shifting behaviour was completely undriveable. The units were replaced without cost, but that didn't help me that much since I got stuck with the car and once I even had to be towed home because the whole 4l80E was locked up. They broke down after about 8 months of use and my supplier never figured out why, but replacing the main unit solved the problem immediately.

I've thrown everything TZI out of my current car and bought USShift. This is also plug and play like TZI, but looks a lot uglier and their website makes you think that it's someone selling their stuff from a garage. Never had a problem since.

After two years of driving I decided to learn how to use a laptop with it. This turns out to be stupid simple and without reading the manual I can really tune the shift behaviour and there is a great burn-out feature on it

[doubleclucker]

Bilfman-
I noticed your crossmember-
The older foot style mount 1/2' 3/4' are the same but the 1 ton one was flatter (like the one you removed.)

But for the newer mount and crossmember (like the one you installed)GM used the same one for the 1/2' 3/4' and 1 ton but on the wider 1 ton frame they mounted it in between the frame rails and used the wider spaced holes. This is how they made up the difference in frame width ,get angles correct and make shifter location the same . When used on 1/2' and 3/4' ton frames they mounted on the bottom of the frame and used the middle raised holes.(hence the 4 holes at different heights on crossmember.) The bushings were used for exactly what dirtylarry had explained earlier on.

[doubleclucker]

some pics- 1st two are 1 ton trucks last is 3/4 ton
(if you look close you can see the bushing placement)

[DirtyLarry]

Originally Posted by Rogier

Two different TZI units broke down on me in two different cars, the easy config settings went all off the chart and the shifting behaviour was completely undriveable. The units were replaced without cost, but that didn't help me that much since I got stuck with the car and once I even had to be towed home because the whole 4l80E was locked up. They broke down after about 8 months of use and my supplier never figured out why, but replacing the main unit solved the problem immediately.

I've thrown everything TZI out of my current car and bought USShift. This is also plug and play like TZI, but looks a lot uglier and their website makes you think that it's someone selling their stuff from a garage. Never had a problem since.

After two years of driving I decided to learn how to use a laptop with it. This turns out to be stupid simple and without reading the manual I can really tune the shift behaviour and there is a great burn-out feature on it

Ah, oh! Hope they got them figured out by now. A guy I know used the USshift in his El Camino and while pulling motorcycle trailer to Sturgis it overheated and the control box got so hot it exploded and caught the seat on fire. It all happened so quickly he couldn’t get out in time and had to have a skin graph on his testicals and rectum. It all just happened so quickly! Not really, I just made that story up because I didn’t want to hear anything bad about the TCI EZ-ECU

I looked at the USshift unit as well. Both looked really nice and it came down to a good price on the EZ unit. We’ll see how well it works. Hope to have the same good luck as bilfman.