The mythical CUCV 4L80E swap

[richingalveston]

you need to move the pivot point of bottom shift linkage back. I had the same problem with mine. The bottom piece (the one that goes into the shift fork on the tranny) will bind in the shift fork and cause it not to shift to 1 and 2.

 

[Dave87]

that l shaped linkage with the spring? that goes between the trans and frame?

 

[richingalveston]

4l80e shift linkage move

here is the bracket I made to move mine. I bolted the bracket to the original hole that the linkage went through. I made it out of some scrap. I may make a better one in the future. the second hole is there because I did not get it in the right place the first time.

 

[richingalveston]

yes, the lower linkage has the cup and spring.

 

[Dave87]

Ok yea i moved that back. i measured the fork on the 400 and the 4l80 to get how far back i needed to move it. it seems to move pretty free when i clime under the truck and move it by hand but when i get everything hooked up it doesn't work so good. the bar that comes off the lower link is in the 7 oclock position when in first gear and in the 3 oclock position when in park. i have a feeling its the block i made. ill have the girl friend shift it so i can put eyes on it while im under the truck. the spring and shift linkage look like they did before just back about two inches or so.

 

[Dave87]

i like the 09 in your pic. looks good.

 

[Dave87]

Ok just an update, I got the bugs mostly worked out. The truck doesnt seem to get any better highway mpg but it runs out nice. it doesnt sound like the motor wants to explode haha. still alittle high for my liking. the stand alone computer works flawlessly. i wanna thank Trueknight and richingalveston for the post and for the help, really good information. Again thank you all

 

[WARWAG]

Do you have a lock up torque convertor? When the convertor locks up that is where you get your fuel economy from.

 

[Dave87]

Yea it locks up. i run down the road at about 70-75, that doesnt help.

 

[Cleptomaniac]

Man I am working on getting the stuff together to do this. The th400 went out on my 1009

 

[WARWAG]

Yea it locks up. i run down the road at about 70-75, that doesnt help.

If your running down the highway at 70-75 MPH and getting the same mileage as when you were running down the road at a lesser speed but at HIGH RPMS then and getting the "same" fuel economy then you are getting better Miles Per Gallon as you are going further per gallon. Try running at the same speed as you were before the 4l80E swap. That will give you an idea on your fuel economy. Trust me. If your running at a lower RPM then your getting better miles per gallon.

 

[Dave87]

yea i can agree with that but the truck is pushing more air. theres no doubt at 65 the truck will do better. it already seems better in town but i dont drive it enough to really gauge in town driving. i mainly put the over drive tranny in to do the highway. i get 15mpg at 70-75 so im happy. i need to slow down to 65, i fear my heads are lifting. might just be in my head. im taking the truck on a trip again in september so ill try 65 to the U.P.

 

[cliffyp]

Stock truck at 55 is turning 2700 rpm's. Same truck with 4L80 at 75 is turning 2700 rpm's. Scale it back a bit and get the engine in the 2100-2200 rpm's and it will be a lot happier. I cruised my 1028 w/700r4 @ 65 and got combined 17 mpg. I never had a chance to do a road trip and see what mpg's I'd get at 65 sustained. Oh well.

 

[brazengoat06]

maybe i missed this somewhere but specifically what torque converter did you use? or does a 4l80 converter bolt up to a 6.2 flywheel?

btw awesome writeup! im going this weekend to grab a 4l80 core!

 

[True Knight]

Thanks. The transmission shop that rebuilt the 4L80 got me the appropriate converter. If I remember correctly the brand was "The converter shop" or something similar. You will want a converter designed for the diesel because the one for a gas engine will have a higher stall speed. GM did put 4L80's behind 6.2/6.5s so you should just be able to order the correct converter. Nothing special.

Have you decided what trans controller you're going to use? There are more options out there now.

 

[brazengoat06]

At this point I think ill go with the TCI unit. I has the same features as the more expensive units but less $$$. Looks like itll run about $730 for everything on the controller side. Unless someone else has a better solution.

 

[True Knight]

It does have a lot of features. Like paddle shift capability. Ha ha, we really need that in this beast! I do want to hook up a trans temp sensor tho.

 

[brazengoat06]

I was looking at how the TCI TPS sensor is setup and was wondering if the stock TH400 kick down cable can be made to work with that sensor?

 

[True Knight]

The 400 is operated by vacuum only. No kickdown cable.

 

[True Knight]

I originally wanted to make throttle pump mounted TPS work, but using the remote sensor was easier.