The mythical CUCV 4L80E swap

rustystud · Jan 20, 2016

brazengoat06 said:
Since no one has the exact specs for the output shaft and 4wd adapter I am kinda halfway shooting in the dark.

Ask and you shal receive !View attachment Scan0048.pdf

brazengoat06 · Jan 20, 2016

rustystud said:
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.

Lol or you can pressure check it before you reassemble the transmission. Are you done yet?

brazengoat06 · Jan 20, 2016

rustystud said:
brazengoat06 said:

Since no one has the exact specs for the output shaft and 4wd adapter I am kinda halfway shooting in the dark.

Ask and you shal receive !View attachment 604276

Click to expand...

I appreciate the info but the 400 has a different adapter. The 9 1/4 shaft would be crazy long. The 2wd 4l80e I have has the 8 1/8

MidnightDuramax · Jan 20, 2016

I have done a 4L80 2 wheel to 4 wheel conversion and also bought no specific tools. It was about 8 years ago so not sure on the specs you are looking for. The one thing I do remember is that there is a plug between the case and tailshaft housing. On a 2 wheel drive there is a pin hole in it to allow trans fluid to lube the tail shaft. When doing a 4 wheel conversion it needs to be changed to one with no hole or the trans will fill the t-case with trans fluid.

brazengoat06 · Jan 20, 2016

MidnightDuramax said:
I have done a 4L80 2 wheel to 4 wheel conversion and also bought no specific tools. It was about 8 years ago so not sure on the specs you are looking for. The one thing I do remember is that there is a plug between the case and tailshaft housing. On a 2 wheel drive there is a pin hole in it to allow trans fluid to lube the tail shaft. When doing a 4 wheel conversion it needs to be changed to one with no hole or the trans will fill the t-case with trans fluid.

I'm looking for the specs on what length of output shaft to use for the conversion.

I do see the hole your referring to, it's a plug in the transmission case. Is there a different plug that I need to attain?

86m1028 · Jan 20, 2016

brazengoat06 said:
I'm looking for the specs on what length of output shaft to use for the conversion.

I do see the hole your referring to, it's a plug in the transmission case. Is there a different plug that I need to attain?

You can get the plug at any transmission shop.

Specs are gonna vary, there are a few different ways to do it.

I used a 2wd 4l80, tall 400 to 205 adapter (fig

.
I had adapter machined, changed the plug & cut down the output shaft of the 4L80.

I also have the rare (91 only) factory 4l80/205 setup but decided to use the newer 2wd 4l80 because of the improved cooling & updates.

If I remember correctly I cut 1/2 to 3/4 inch off the 2wd shaft.

brazengoat06 · Jan 20, 2016

I found the plug your talking about. Thanks for the heads up, the tech book is not so clear on that. I'll pick that up tomorrow.

icer97 · Jan 21, 2016

brazengoat06 I am also doing the swap as we speak in my cucv and also have a 2wd 4l80e transmission. My output shaft is the 6.5in fully splined so I plan to cut my shaft down to length rather then tearing it down to replace it with a 4x4 output shaft. I plan to run my 208 and see about having the 400 to np208 adapter milled to bolt up the the 4l80. If this is a big deal as I have heard the mounting feet may contact the 4l80 pan, I found the part number for the gm 4l80 adapter that's around $60 from gm.

brazengoat06 · Jan 21, 2016

86m1028 said:
You can get the plug at any transmission shop.

Specs are gonna vary, there are a few different ways to do it.

I used a 2wd 4l80, tall 400 to 205 adapter (fig .
I had adapter machined, changed the plug & cut down the output shaft of the 4L80.

I also have the rare (91 only) factory 4l80/205 setup but decided to use the newer 2wd 4l80 because of the improved cooling & updates.

If I remember correctly I cut 1/2 to 3/4 inch off the 2wd shaft.

I got the transmission and transfer case mated to confirm that to do a 2wd-4wd 4L80 conversion you will need the 2 5/8 adapter housing and the 3 3/4 output shaft. Now as for Plugging the orifice in the rear of the case, i have been unable to locate a transmission parts supplier that can find this part. It seems that it is not servicable. However looking at my case I see a very large drain back below the orifice that should be more than plenty to drain whatever comes out of that hole. I saw that you said that it filled up your Transfer case? That confuses me because between the drain, the input shaft seal, and how tiny that orifice is, im not sure how that happened. Im not trying to sound like im questioning you but more so trying to understand how it happened. Thanks

MidnightDuramax · Jan 21, 2016

It didnt happen. Whent to my local trans shop to pick up the parts to do a rebuild and conversion he told me about the plug. He was the one that said it would cause problems and fill the case if not changed out and had the plug to give me. Like I said it was 8 years ago and I have trouble remembering what I did at the begining of the week so can't really remember where it was located or how it would cause a problem. All i do remember is him telling me this and having the replacement part for it.

MidnightDuramax · Jan 21, 2016

Quoted from another forum. "and 2wd needs the oil plug swaped out on the 3 oclock position with the tail housing off. 4wd needs a solid plug. 2wd has pin hole to lube the bearing in the tail housing. "

MidnightDuramax · Jan 21, 2016

After a little more searching and it seems to be refered to as a lube cup orifice.

brazengoat06 · Jan 21, 2016

Thanks for the feedback!

rustystud · Jan 22, 2016

brazengoat06 said:
Lol or you can pressure check it before you reassemble the transmission. Are you done yet?

I'm curious brazengoat. How many automatic transmissions have you rebuilt ? If you have built more then one then you would realize that the seals can be damaged from a faulty install and still pass a air pressure check on the bench. It's after it has been run awhile that the damaged seal will let go.

icer97 · Jan 22, 2016

I had a guy on another forum that's done the 2wd to 4wd conversion tell me to make sure to plug the drain hole in the rear housing also. He said he popped out the plug with the hole and took it up to the local parts store and sized it up to some freeze plugs until he found one close to size to drive in place to block the oil passage. According to him not only do you have to worry about oil passing back and forth but a loss in line pressure due to it also.

brazengoat06 · Jan 22, 2016

rustystud said:
I'm curious brazengoat. How many automatic transmissions have you rebuilt ? If you have built more then one then you would realize that the seals can be damaged from a faulty install and still pass a air pressure check on the bench. It's after it has been run awhile that the damaged seal will let go.

Enough of them.

MOST 99% seals that pass an air check on reassembly will last the life of the transmission. I find it funny you haven't even bothered to ask what method I'm using to install the seals yet would rather argue. The method I use is just as reliable as an installer but your more than welcome to do it the more expensive way.

brazengoat06 · Jan 22, 2016

icer97 said:
I had a guy on another forum that's done the 2wd to 4wd conversion tell me to make sure to plug the drain hole in the rear housing also. He said he popped out the plug with the hole and took it up to the local parts store and sized it up to some freeze plugs until he found one close to size to drive in place to block the oil passage. According to him not only do you have to worry about oil passing back and forth but a loss in line pressure due to it also.

Yes seems like I just read a similar thread last night. Not sure how true it is but it's definitely plausible depending on the oil passage that it's tied to, so I am gonna try and do the same and find a freeze plug.

rustystud · Jan 23, 2016

brazengoat06 said:
Enough of them.

MOST 99% seals that pass an air check on reassembly will last the life of the transmission. I find it funny you haven't even bothered to ask what method I'm using to install the seals yet would rather argue. The method I use is just as reliable as an installer but your more than welcome to do it the more expensive way.

Well then give use some pictures and a statement of how it's done. You have me curious now. Actually I'm all in favor of a good and cheap way of doing things so long as it really works reliably .
Though I do question your 99% . I have found out doing tranny rebuilding now for 40 years that the actual number is more like 80%. Doing air-pressure checks is just some added insurance of a good rebuild, not a guarantee.

brazengoat06 · Jan 23, 2016

Found this while awaiting the birth of my son... A bit pricey but would make a clean install. Any thoughts?

http://www.amazon.com/ACDelco-215-97-Original-Equipment-Driveshaft/dp/compatibility-chart/B000EQRSVY

rustystud · Jan 24, 2016

I was actually waiting for your seal installer, but yes this looks like it will work.

The mythical CUCV 4L80E swap

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