I have a known good core tranny from a 99 V6 Firebird. I know the input shafts are different, but are there other internals or connectors that need to be changed for 4th gen LS1 usage?

 

From a Buick 3.8L V6 to LS1...

To physically bolt together, you need:

-Bellhousing
-Stator support
-Turbine-shaft
-Torque converter
-Flex plate

You are probably going to have a 3-4 clutch failure due to the lower capacity 3-4 clutch assembly installed in the V6 cars.
I would replace the 3-4 clutch assembly with one for a 4L65E.
You should also at least install a new Sun shell, and forward sprag (dual cage 29 element).
I would also at least replace the V6 servo for the 2-4 band with a Corvette servo.

 

Great post, thanks - just the kind of info I was looking for. Besides the other things you mentioned, if the 3-4 clutch pack is different and needs to be replaced, then per that fact the tranny needs to be gone through, rendering it next to worthless for an LS1 application. If it was a matter of replacing the bellhousing, input shaft, drilling out the separator plate and a few other odds and ends, that'd be one thing. But basically it needs to be rebuilt to V8 specs to be useful.

 

I don't believe the 3-4 clutch pack is different from what I've seen. See the pic below - 6 frictions, same as a V8.

The problem is you have to empty out the drum they're in to change the shaft. The only thing thats notably different is the valve body calibration, but a shift kit can change all that.

 

Okay - good info - thanks!

 

The majority of the V6 vehicles had a 5 friction 3-4 clutch assembly.
Some did have 6, most do not.



The 5 friction units have:
-Six 0.106" steel plates
-Five 0.082" friction plates
Along with thicker apply plate and backing plate.

Both the 5 friction units and 6 friction units should be upgraded to the original "4L65E" configuration for stock V8 engines and built upon more for higher output engines.

The 4L65E 3-4 clutch assembly has:
-Six 0.097" steel plates
-Seven 0.065 High Energy friction plates
Along with thinner apply plate and backing plate.





The majority of the V6 vehicles also have a smaller intermediate servo.
Some have the servo normally found with V8 engines.



Both the V6 and V8 units should be upgraded to the Corvette intermediate servo for stock V8 engines. With some orifice size changes, the Corvette intermediate servo can handle modified V8 engines as well. V8 engines making more power can benefit from a Sonnax intermediate servo.
Sonnax part # 77911-03K
The over-drive servo can also be upgraded to a Sonnax over-drive servo if desired.
Sonnax part #77767K




The original sun-shell in any of the 4L60E transmissions prior to 2005 (some trucks with high output engines already upgraded) should be upgraded to a GM heat treated/ hardened sun-shell.
The original sun-shells are just a weak link item that could fail at any time and should always be replaced.
Sonnax also offers a rollerized version of this part.
The GM part will also require a new reaction-shaft and bearing to complete the upgrade.
GM parts #24217145, #24217157, #24217328
Sonnax part #77749-02K




Lastly the forward sprag is also a part that should be replaced during every rebuild. There are 2 different GM sprags to use as an upgrade.
I do not consider either sprag to be actually adequate, however they last for a while and there is no aftermarket solution currently.
Should the 3-4 clutch hydraulically every get corrected/ improved... this sprag/ overrun system for 3rd gear is going to need improving.
Latest GM 4L60E forward sprag: #8657928
Latest GM 4L65E forward sprag: Borg Warner part #50120BW

Sorry I do not have the GM part number at the moment.

While I believe the 4L65E part to be better, It is only so by a very minor amount.

 

If you have a 4l60e with 60k miles...you can bet it has issues in the valve body from wear.
You can bet the sunshell is still a physically weak part of the trans...you can assume the input sprag is a physically weak part of the trans...you can assume the servo size will be too small of a ratio.
Those things don't really matter if they're 60k or 600k mile parts

Servo, sprag, and shell upgrades are very inexpensive parts that will lend a hand to the longevity of any 60e based trans.
And why wouldn't you treat every trans the same regardless of miles.
-inspect all bushings
-inspect all thrust areas
-replace clutches and steels
-repair valve body and pump with necessary parts to vacuum check properly
-inspect planetaries for thrust wear and pinion wear. Replace/repair as needed.
-pump and sungear bushing EVERY time
-inspect pump pocket and machine if necessary
-etc etc

The list of things you inspect and change (if needed) should be very consistent for any 4l60e

 

so...you're saying there has been bad advice in this thread?
Nobody said replace everything?

The differences were listed...and it was recommended to replace/upgrade
-sunshell
-servo
-3/4 clutch pack
-maybe input sprag

That's it

Seems like an incredibly reasonable list considering this transmission's history and track record. If you replace/upgrade those 3 or 4 things, and do a cheap rebuild like you've mentioned...you'll likely be fine.
Nobody said replace every part in the whole thing...just a list of 3 VERY common failure modes and how to fix them for not alot of money. Vette servo, sunshell, and a 7 stack 3/4 clutch are CHEAP upgrades.

 

Yes I agree with that...a new sprag is CHEAP. for anybody taking the time and energy to pull and rebuild a trans, they should at least get a dual cage. if you ever have an issue, you'll spend more in fluid when you drop and tear apart the trans than you ever would in buying a new sprag.

your sprag in the 700 would be supported by the overrun clutches in 1, 2, 3...or if you left it in d3 and let it autoshift. Also, we shouldn't take the exception as the norm.
I've seen lots of trucks come in with worn out, rolled, shattered, etc input sprags. The cheapness of the part and the improvement you get for the money...seems like a no brainer to me.

If you're trying to argue what you can get away with if you're trying to be the cheapest bastard to ever rebuild a 4l60e...get 2 or 3 free cores from people looking to clean out their garage on facebook marketplace, or craigslist...tear all 3 down. Make a pile of the best clutches, pick the best band, and reassemble. Put a half turn on the epc, hope the valve body in one of the 3 is ok, i'd recommend going with whichever one smells the best cuz why not...then slap it all together with reused seals everywhere. You'll have a free rebuild, less your time.
If it works...congrats. Looks like no new parts were necessary...lets tell everybody they can rebuild one for free if they just "do what I've done and got away with"
Let's not tell people the right way to do it, or recommend some inexpensive and worthwhile upgrades.

sounds silly to me...but if that's your way of doing things, then cool.

-good used or new GM heat treated sunshell
-corvette servo
-7 clutch 3/4 stack
-new input sprag
-pump bushing
-extra sungear bushing (just drive it in on top of the one that's there)

These are things I would recommend for anybody on here asking about a rebuild. That's likely less than $75...for sure less than $100 in parts. For ALOT of "peace of mind"
If someone on here can't swing 100 bucks for the life and longevity of a trans...then they can use your method where we only replace the bare minimum then brag on the internet when "it works my way for less money"

IDK Jays, you seem moody lately...not sure which one of us guys spit in your cereal, but I'm sure it wasn't on purpose

 

My job isn't selling parts either?
Building transmissions isn't even my job...I'm a desk jockey 9-5...there weren't pages trying to "prove you wrong"...there's no boogyman out to get you. Just other guys sharing info and their experience. Relax a little bit, share the info you have, everybody else will do the same, and soon there will be very few questions left for the 60e

 

you can handle it. I've seen you post. Hold your own...or maybe I'm a little too forward, treating this like it's "the bullet"