4L60E/241C info

[First c10]

Here is one of the braces clinebarger talked about. I got this with my TC out of the 91 burb.

[A1971Blazer]

Originally Posted by First c10

This is the mating surface of the TC 241c.

Is the top mount hole at 12:00 o'clock? If so I think the adapter clinebarger posted a link to will work.

The TC is scheduled to be delivered tomorrow and there were 10 of those adapters available on Ebay. I think I may be getting closer......

Also the bracket you show in the post above........is it like a torsion bracket that would go from the TC to the frame? I've got all kinds of steel material to fab brackets from if I can just figure out how it needs to be braced.

The old NP205 had a torsion mount on the right side between the TC and the frame.

BTW, thanks for all the good info.......much appreciated!

[First c10]

If you look at the trans picture I posted there is no 12 o'clock bolt hole. More like a 11 and 1 o'clock. After I rebuilt the TC i bolted it up to the 4l60e trans and factory 2008 adapter and it looked good. I can't remember what position the front drive line yoke was but looked correct when I set the 1991 burb crossmember under it.
The second picture was a bracket that went to both halfs of the TC case (Hense the 2 holes at one end) the other end went to the transmission to engine bell housing bolt. Not to the frame.

[A1971Blazer]

Originally Posted by First c10

If you look at the trans picture I posted there is no 12 o'clock bolt hole. More like a 11 and 1 o'clock. After I rebuilt the TC i bolted it up to the 4l60e trans and factory 2008 adapter and it looked good. I can't remember what position the front drive line yoke was but looked correct when I set the 1991 burb crossmember under it.
The second picture was a bracket that went to both halfs of the TC case (Hense the 2 holes at one end) the other end went to the transmission to engine bell housing bolt. Not to the frame.

OK......great.......thanks! As long as the adapter mount comes parallel to the cross member it should work as long as it's clocked such that the drive shaft and all will clear.
The bracket looks like it's some kind of stiffener to perhaps offset some torque when the 4WD is engaged.....

I'm probably doing too much thinking.....just need to wait for the TC and go forward from there......

[First c10]

Originally Posted by A1971Blazer

OK......great.......thanks! As long as the adapter mount comes parallel to the cross member it should work as long as it's clocked such that the drive shaft and all will clear.
The bracket looks like it's some kind of stiffener to perhaps offset some torque when the 4WD is engaged.....
The brace I think just holds the TC together with the trans/motor, as far as torque I am not sure this really would support rotational torque. More of a triangular support for the aluminum TC would be my guess.

I'm probably doing too much thinking.....just need to wait for the TC and go forward from there......

You are probably thinking to much!!!! Sometimes you just need to get your feet wet!!!

[First c10]

Originally Posted by A1971Blazer

Thanks....!
I'm not sure about the picture...I put the wrong one, deleted it, then put in the correct one......who knows......?
I asked the seller to throw in the adapter....hopefully he will.....just in case it's the correct one.
Another try.......back of 4L60E tranny case
Attachment 1378496

Picture from post #18
Also I was thinking that you may need a different seal and plugs to stop the trans fluid at the transmission before it gets to the output shaft. my sons 6L80E I had to remove the seal and plugs so that I would have fluid to the tail shaft. I converted from a 4x4 trans to a 2x4 trans..
Hopefully someone has performed this conversion on a 4L60E can chime in!
I guess I can look at the tail shaft on my 4L60E at the shop.... I will try and take picture tonight

[A1971Blazer]

Originally Posted by First c10

Picture from post #18
Also I was thinking that you may need a different seal and plugs to stop the trans fluid at the transmission before it gets to the output shaft. my sons 6L80E I had to remove the seal and plugs so that I would have fluid to the tail shaft. I converted from a 4x4 trans to a 2x4 trans..
Hopefully someone has performed this conversion on a 4L60E can chime in!
I guess I can look at the tail shaft on my 4L60E at the shop.... I will try and take picture tonight

That was another consideration....because I'm doing the opposite....converting a 2WD to a 4WD.....I just assumed the fluid migrated into the cavity in the adapter since it has an o-ring at the tranny and a gasket at the TC mount?

[First c10]

Originally Posted by A1971Blazer

That was another consideration....because I'm doing the opposite....converting a 2WD to a 4WD.....I just assumed the fluid migrated into the cavity in the adapter since it has an o-ring at the tranny and a gasket at the TC mount?

My 6L80E Had that same configuration(o'ring and gasket) but had a seal at the shaft and no other opening in the trans to adapter...

check this out. This is what I did!
6L80E conversion to 2wd from 4wd

[clinebarger]

Originally Posted by A1971Blazer

That was another consideration....because I'm doing the opposite....converting a 2WD to a 4WD.....I just assumed the fluid migrated into the cavity in the adapter since it has an o-ring at the tranny and a gasket at the TC mount?

No mods needed, The T-case has a seal to prevent the Trans & T-case from swapping fluid with each other. The Trans case has a drain hole to drain the fluid from the adaptor.

[A1971Blazer]

Originally Posted by clinebarger

No mods needed, The T-case has a seal to prevent the Trans & T-case from swapping fluid with each other. The Trans case has a drain hole to drain the fluid from the adaptor.

So basically all I need to do is swap the output shaft on the 4L60E to a 4wd?

Also what mods would you recommend doing to the 4L60E while it's apart. The LS1 will remain stock and I plan on running 33" tires with 4.56 gears.

[clinebarger]

Originally Posted by A1971Blazer

So basically all I need to do is swap the output shaft on the 4L60E to a 4wd?

Also what mods would you recommend doing to the 4L60E while it's apart. The LS1 will remain stock and I plan on running 33" tires with 4.56 gears.

Yes, Just the output shaft.


Sonnax, Smart Shell (Reaction Sunshell), 77749-02K
Sonnax, Performance pack, HP-4L60E-01
Sonnax, Wide sungear bushing, 77010-01
Sonnax, Wide rear stator bushing, 77002BT-01
Sonnax, Front stator bushing, 35007A
Sonnax, Input drum reinforcement kit, 77733-51K
Sonnax, Front pump bushing, 77005T
Borg Warner, 29 element input sprag, 29236AM

Most true LS1 4l60E's have a "093" Corvette 2nd servo piston. If the 1-2 shift is to harsh for your liking.... Get a "159" Trailblazer SS 2nd servo.

Hi-Energy frictions for the 3-4 clutch, 7 & 8 count stack-up's work well.

Raybestos, Borg Warner, & Alto make friction modules with Hi-energy frictions.

2/4 Band... Pick your poison.

[Mjminino]

ill trade you i have a 4l60e 4x4 with transfer case and i need a 4x2 4l60e mine came from a 2001 suburban. meet half way or something i am located in Omaha Ne

[A1971Blazer]

Originally Posted by Mjminino

ill trade you i have a 4l60e 4x4 with transfer case and i need a 4x2 4l60e mine came from a 2001 suburban. meet half way or something i am located in Omaha Ne

Thanks for the offer but mine is already disassembled and being prepped for rebuild.

[Mjminino]

dang, too bad we didn't get in touch earlier, would have saved us both time and money!

[A1971Blazer]

Originally Posted by Mjminino

dang, too bad we didn't get in touch earlier, would have saved us both time and money!

......story of my life.......day late, dollar short........

[A1971Blazer]

OK.....got the transfer case today......looks well used and as if it's been apart before?



Here is the adapter that was on it...700R4 early 4L60...


Looking at the adapter and bolt circle on the TC, it looks like the top hole will clock a 12:00.
That means the adapter will likely need to be.......... THIS ONE......... maybe.....?......looks like it would clock it correctly.

[clinebarger]

Looks like the stock late 4L60E adaptor will work, That will eliminate some work....Though it looks like you work in some kind of machine shop?

[A1971Blazer]

Originally Posted by clinebarger

Looks like the stock late 4L60E adaptor will work, That will eliminate some work....Though it looks like you work in some kind of machine shop?

Good catch!.....I actually own a small CNC manufacturing "job shop."
It's me, my son and another guy that's been with me for 10 years. We do contract machining for industrial customers.

Pretty much just make parts to their specifications. It's a living...plus I get to buy some cool tools and stuff for me on the company's dime.

Unfortunately I stay so busy that I don't get to do as much of "fun" stuff as I would like....

Thanks again for all your advise/input......it is much appreciated......probably be looking for more before it's over....

[First c10]

This is the part number to the 2008 TC adapter

[First c10]

Here is a side view of my adapter install from the factory on the 4l80e.

[A1971Blazer]

OK........I ordered an adapter off Ebay that I think will work....we'll see?

Meanwhile, I did a quick teardown to look inside.......all looks good.......bearings feel good but I will probably replace them and the seals just because. Magnet had very little sludge and no big steel particles. Synchronizer looks good too. I think I did OK....

Looking at the rebuild kits......there are two different input bearings.....I needed to pull it out to measure for the correct one.

What is the tolerance for chain slack? It's been awhile since I worked on a chain drive TCs but this one seems to have a little more slack than I remember them having?

Anyway a quick trip to the bead blast cabinet and it's starting to look like new.



First.......what kind of paint did you use on yours?
I was looking for something that will stick on aluminum?

[First c10]

Correction to my earlier post. I have a 4l60e not 80.

[First c10]

Looking good. I used VVT engine primer and paint. I also bead blasted my case. I ordered a complete kit and changed all bearing and seals. I am not sure on the chain I can't remember what I found when I did mine but it was in good shape so I did not replace it. I wish I had taken pictures but I didn't have camera or my phone with me when I rebuilt it.

[A1971Blazer]

Originally Posted by First c10

Correction to my earlier post. I have a 4l60e not 80.

I was thinking when I saw that........."that looks exactly like the rear of my 4L........."

[A1971Blazer]

Now.......Do you have the front output flange or yoke? This one has the square flange.

I need to find a CV yoke for the front output. JB conver... has one that measures the same but specifies it as a rear yoke, pretty sure it would work.

I like the CV driveshafts.......much smoother.

I found a real good CV joint shaft that we cut off something. Also have a '79 F250 front shaft with a good CV.
The one on the right is the K5 factory shaft.......CV is shot.
The left one I found when I started cleaning my barn to put the lift in.

Spicer