ANGRY BIRD

iTrader: (2)

Why do I ask?

I have 2 3.8 transmissions, on I overhauled with a TCI master overhaul and a B&M transpak. I would much rather have that one in my Z28 than the stock transmission that acts funny. I also have a corvette servo and TCC plunger waiting to be installed in it.

All three of my transmissions are the 3 peice casting types so the bellhousings can be interchanged I assume. A friend of mine said that the v8 version was built "stronger". I have never heard such a thing. As far as I know a 4l60-E is a 4l60-E.

If it isnt obvious I'm a previous V6 guy and I noticed the kickdown are a lot "lazier" on the V8. I assume it's for better gas mileage?I know it drives me crazy when I want to command a downshift with the foot and it doesn't downshift, or far enough. Then I gotta romp into it and next thing I know i'm screaming passed every car on the road lol

One other thing, my Z28 shifts perfect normally, but when cruising at highway speed when I give it a little extra gas to unlock the TCC to pass it makes a pretty hard clunk unless I romp it enough to get it to kick down a gear or two.

mrvedit

There are three INCOMPATIBLE versions of the 4L60E which depends upon the input shaft as can be seen in this picture:



In short, the 298mm input shaft, used in all pre-'98 transmissions and later V6 applications will not directly work with an LS engine. It will work if you use an LT1 converter and a spacer, but not directly. While there is no "strength" difference between a V6 and V8 version from the same year, later years are stronger as GM made improvements, first to handle the LS1 engine and later to handle the LS2 engine.

I would highly suggest trading/selling your 298mm input shaft trans and getting a '98 or later 300mm input shaft trans, preferably am '03 through '06. (Some '06 and all later ones will be incompatible with your PCM.)

ANGRY BIRD

iTrader: (2)

Hmm both trannys are 99's

LongIsland63SS409

iTrader: (22)

To clarify if you have a 1998 and later 30 spline V6 trans all you have to do is switch to a LS1 bell housing and your good to go?

Mike

mrvedit

No! A V6 trans has a 298mm input shaft. It WILL NOT fit an LS-compatible converter.
The input shaft cannot be changed without rebuilding the trans.

Assuming you want to use an LS-compatible converter, you MUST use a '98 or later trans from a V8 vehicle which will have both a 300mm input shaft -AND- a bolt hole in the 12-O'Clock position in the bell housing. Just changing the bell housing is not enough.

LongIsland63SS409

iTrader: (22)

Thank you I read the blue post it again. Time for new glasses.
LOL

Mike

ANGRY BIRD

iTrader: (2)

Damn that sucks. Thanks for the help guys.

ANGRY BIRD

iTrader: (2)

So apparently they make a spacer that makes the pre-98 transmission compatible with the LS. It's sold on Jegs. A bud told me about it and he said his friend just used one last month.

http://www.jegs.com/p/Chevrolet-Perf...35483/10002/-1

mrvedit

Based on many threads here, you need the spacer, longer crank bolts and need to elongate the holes in your flexplate to mount the converter. (Do that when/where you have lots of room, not last second.)

You said the trans is a '99 which should work fine with your PCM.
Just to be thorough, a pre '96 (specifically valve body) will not work directly with your PCM; there are ways around that too, but I don't know the details.

I guess I or someone else could have pointed this out earlier, but since I don't have personal experience with this, I don' t know what other "surprises" there might be.

ANGRY BIRD

iTrader: (2)

What do you mean by elongate the flexplate holes?

mrvedit

Who knows these details?

As I understand it, the LT converter mounting holes are on a very slightly different diameter the the LS mounting holes on your flexplate. Perhaps 1/16", but I don't know in which direction.

ANGRY BIRD

iTrader: (2)

But I don't have a LT converter. It would be LS converter LS Flexplate Adapter Engine.

Not grasping why it wouldn't bolt up if it's LS stuff.

mrvedit

An LS converter DOES NOT fit on a 298mm input shaft, which you indicate you have.

Only LT converters fit on 298mm input shafts.
A custom converter could be made for you, but it will not be a stock item.

ANGRY BIRD

iTrader: (2)

Ok, just had a conversation with JEGS.

Ray1:07:52 PM
What engine and transmission are you running?
John1:08:18 PM
My car is a 1999 Z28 LS1 to 4L60-E
1:09:42 PM
I have a spare transmission from one of my 3.8 builds. It's a 1999 4L60-E for the V6 which I understand is that same input shaft as the LT. So I wanted to use the adapter to use that transmission with my z28
1:11:15 PM
I understand that I will need to swap bellhousing of course, but Im getting some misleading answers. One being "An LS converter DOES NOT fit on a 298mm input shaft, which you indicate you have.
Only LT converters fit on 298mm input shafts.
A custom converter could be made for you, but it will not be a stock item."
1:12:01 PM
So how does one use the LT/ V6 version of the transmission besides of needing the spacer?
Ray1:12:32 PM
You need to use a flexplate like 809-19260102 and a 4L60E torque converter.
1:13:10 PM
And the spacer part number 809-12563532 and bolts 809-19257940
John1:13:26 PM
is that a LT torque converter, or LS?
1:13:34 PM
I mean flexplate
Ray1:14:10 PM
It is an LS flexplate
John1:15:45 PM
but they are saying a LS converter wont fit the 298mm input shaft, I know the LS input is 300mm. I just want to get this right before I spend money yank it out and it doesnt work
Ray1:16:38 PM
You don't use an LS converter. You use a conventional converter for the 4L60E. As long as you match the converter to the trans it will be fine.
John1:18:38 PM
So the one that came WITH the Z28 wont work, but the one that came with the V6 transmission will? It wont effect stall speed or performance/ life of the converter made for the six?
Ray1:20:15 PM
If you are using the V6 transmission then you should be able to use the V6 converter with that flexplate. You will want to verify the converter bolt pattern first so we can be sure it will fit the flexplate.
John1:20:43 PM
They seemed to make it out that the holes for the LT/LS dont line up together
1:20:58 PM
between converter and flexplate
1:21:19 PM
which is where most of the confusion is coming from I believe
Ray1:23:37 PM
That is why you should measure the bolt pattern to be sure. Usually customers who do this swap also buy an aftermarket converter.
John1:26:14 PM
Hmm ok so a sure combination would be LS1-LS1 Flexplate-(aftermarket converter)-Transmission. If that is correct, do you have an example of a converter that will fit this application?
Ray1:30:34 PM
Well, the for sure combination would be the 809-12563532 spacer, 809-19260102 flexplate, 809-19257940 bolts, and an aftermarket converter for the transmission that you are using with the conventional early bolt pattern. I'm afraid I can't say whether any other combination will work.
John1:31:44 PM
so would the after market converter be a LT or LS pattern is what im getting at
Ray1:32:08 PM
It would have to be the early pre-LS bolt pattern.
John1:33:55 PM
Ok, that makes things a bit more clear. So I will need to find a converter that fits a 298mm input and has pre-LS bolt pattern. Are those readily available or something that would have to be made custom?
Ray1:37:15 PM
One moment and I'll check.
1:42:29 PM
Thanks for your patience. The V6 input shaft is different so you will need a custom converter built with a V6 spline and a V8 snout. We can have it done by FTI.
John1:43:06 PM
Damn
1:43:56 PM
How would I look into that?
Ray1:44:51 PM
All you need to do is call our technical sales staff at 800-345-4545 and tell them what stall you need. They will contact FTI and take it from there.
1:46:10 PM
Have your salesman contact me if they have any questions. The pricing is the same as the standard LS style V8 FTI converters.
John1:46:52 PM
Ohh cool so it wont cost more for a custom converter?
Ray1:47:20 PM
No, they don't charge extra for it.
John1:48:46 PM
Awesome, thanks for the help. I'll take a look into it further.
Ray1:49:11 PM
Thanks and have a good day.

mrvedit

The advice from JEGS seems to be correct.
So do you have the LS converter or not? You said you did, which prompted my post #13.

FTI and various other converter manufacturers will make you a custom converter as most of these smaller companies custom build it to your specs anyway.

Since you have the ability to build transmissions, IMHO, why not just buy a used 300mm input drum and matching pump and bell housing ($350 total?) and build yourself an LS compatible trans that uses standard parts and bolts right up.
This especially makes sense if you already have a quality LS converter.

All these confusing details is why I discourage people from hooking up a 298mm (LT) trans to an LS engine.

If you do decide to get a custom converter made, just contact the company directly and skip JEGS.

ANGRY BIRD

iTrader: (2)

I was in an automatic transmission class when I did that, built it at school. I don't personally have what I need to do it right.

My LS converter has 125K on it. it would be wise to replace it while the transmission is out.

Yeah I emailed FTI last night, no reason to go through Jegs unless they can have it get done faster. Still waiting to hear back from them.

willt78

So will converter from 298mm shaft work with the 300mm shaft?

PBA

If you are going to rebuild the LT series transmission and want to change it to a LS series. You will need a new LS stator support, to install in your pump. The LS input shaft or the LS input drum with the shaft, and the LS bell housing. The used input shaft with or without drum is $45.00. The used LS bell housing is $85.00. A new stator support can be had for $47.00. You can get these used parts at Teal Automotive in Indiana. Their PH# is 765-768-7726 Ask for Sheryl.