Been lots of question on this, and this is what I have found.

So you have your new Gen III motor and want to run a early auto transmission with it.

There is lots of confusion on this! I need this spacer or that flexplate or this converter.

Really all you need is the right Stock GM flex plate and spacer.

The Gen III/IV has a different crank offset vs the Gen I SBC. Granted this is a manual trans it is still is a good example.



Basically its .400 in. from the were the SBC crank flange location.

So to use the 4l60e with the Gen III GM changed the torque converter by adding a longer nub on the center hub that contacts the crank to support the TC. As well as going with a metric TC bolt spacing.

Gen III converter with long hub


SBC converter note smaller shorter hub


Gen III engines with a stock 4l60/65/70 GM uses a dished flex plate. Note its the one on the right with the shorter crank bolts. The flat flex plate is on the left note the longer bolts.



On Gen III engines using the 4l80 trans which uses a convter with the Gen I style center hub GM used a Flat flex plate and a spacer mounted between the crank and flex plate. This mounts the TC flush with the center hub and it slides into the spacer to support it.


The flat flex plate has the spacer on the fwd side facing the crank.


Dished 5.3L flex plate mated to a SBC Gen I converter. Note the hub is un supported


Flat 6.0L flex plate and spacer on a SBC converter. Note hub is supported by the spacer.


Note the flat flex plate on the right with dish facing up vs dished flex plate with its spacer on bottom. They set almost flat as the dish makes up for the .400 as does the flat units spacer






So you want to bolt your 700r4/TH350/TH400 to a Gen III motor.

Well your in luck!

You have two options using stock GM parts.
1)Use a the dished flex plate and add the spacer after the flex plate. The spacer serves to just support the center of the SBC TC only.




Spacer from GM parts direct or local dealer
GM PART # 12563532
CATEGORY: Engine Flywheel
PACK QTY: 1
CORE CHARGE: $0.00
GM LIST: $52.86
OUR PRICE: $31.34

BOLTS (need six)
GM PART # 12563533
CATEGORY: All
PACK QTY: 1
CORE CHARGE: $0.00
GM LIST: $6.86
OUR PRICE: $4.06

2) Use a 6.0L flat flex plate with the spacer between the flex plate and crank. Note:the spacer is part of the flex plate ie its installed onit and should come off with it.

Another option for a spacer is a spacer/busing it doesn't need longer bolts and just sits in the end of the crank. So its a lot cheaper option at $20.

http://paceperformance.com/i-6520249...nk-spacer.html


The spacing of the two flex plates when attached to the crank are the same IE the teeth of the both flex plates are in almost the same location. The dish of the 5.3L flex plate makes up for the spacer. So any Gen III starter should work.



Now you will still have to elongate the flex plate to TC holes as the spacing for the Gen III TC is metric. Not much will be need, test fit it first on the TC.

And from what I have seen you just can't use a Gen III 4l60 TC in an earlier trans.

There is a couple of kickers. Some early 99-2000 4.8L and 6.0L had a longer crank flange to make up for the .400 inches. If your motor happens to be one of these all you need is the flat flex plate and remove the spacer.

And you really have no way of running a DBW TB with a TV cable. Its easier just to use a Gen III trans.

 

I have had to do this with my flat flexplate and GM adapter, I had to elongate the holes.. how safe is this? Not done much with autos before.

 

Btw you can also use an old style 4L60E (ie LT1 style) using the same method but you will need to switch the wiring harness inside and the 3-2 downshift solenoid so the LS1 computer will run the old style...

 

How about if you are putting a 4L60E behind your engine, get a 2002 F car flexplate, bolts and torque converter. If you putting and 80e behind it, use the 6.0L truck flexplate, bolts and spacer/hub.

 

I've been meaning to do a write up on this because I get so many questions on it... I vote sticky.

Nice job.

One bit to add when you are looking at used transmissions is thinking of how it will be controlled. If you want to have the transmission controlled by the Gen III / IV PCM it needs to be a transmission that has a Pulse Width Modulated front pump and matching torque converter. The easiest spotting feature is looking at the casting on the front pump and noting where it says "PWM" as circled in the first photo below.



Closeup of PWM


If you look at the input shaft of this transmission you can see from the first photo it is for a non Gen III / IV engine by the input shaft (this one happens to be a 1997 from a 5.7 Gen I Vortec truck) and as such needs a spacer. The Gen III / IV input shafts don't have the small ring machined in the tip. The shape and size of the last section is also slightly different and larger. These differences will be obvious if they were compared side by side but I don't have a photo of a Gen III / IV input shaft. I am told the torque converters will not interchange but can not verify.

 

So if you want to use a LT1 style 4l60e on the Gen III engine, which converter do you use?
I have a performabuild stage 2 i want to you but now I'm not sure on which way to control the converter.

 

The easiest way I ID the 4l60's as Gen III is if they have the TQ converters installed most times, is by looking at the center hub. Gen I/II will be pretty flat the Gen III/IV will be really long.

I have "heard" as well that the verters won't interchange.

 

Man now Im more confused =(

 

GEN I/II vs GEN III/IV 4L60E is very easy to spot. Newer trans have the 360* bellhousing, while older ones have the removable dust cover

 

This is not completely accurate, but it is a good "safe" method for locating the right one.

As I mentioned earlier, mine was a 1997 from a Gen I truck that has the 360* housing. I used to think the same thing until I found a few like this one. I think the 360* housing started in 1996 or 1997... not sure though. I know all 3 piece case (removable bell, center, tail) transmissions are the "new" PWM style internals which is really what matters to the PCM for most of us.

Don't forget the "new" style 4L60E transmissions have a six bolt tail housing while the older ones are a 4 bolt. New style 4L60E's also have "M30" cast on the side of the case while 4L65E's say M32 and 4L70E's say M70.

Don't waste your time with a 4x4 trans in a 2x4 application, the output shaft is different and replacing it requires a complete tear down. The bright side is the case and internals are otherwise the same.

A bit more reading for those who are interested.

Hopefully this answers more than it confuses.

 

I know this thread is old but it has some dang good info

 

AMEN....

 

Wait a minute.....shiet....Ok I have a 700r4 with 3000 9.5" converter......Also have a 2004 LQ4 that came with the flexplate......Do I need to purchase another flexplate OR do I only need to buy the spacer and use the 6.0 flexplate that is already attached to the engine????

 

Just to add something. You mention the option of purchasing the new flat flex plate from Hughes. I did this for mine. The Hughes plate is drilled for various TC applications. No drilling required with this aftermarket plate. I paid under $150 for it. ARP bolts were $35 or so.

The TCI plate was nearly $250 so I never looked at IT.

 

Negative!!! I never stated buy the Hughes flexplate! I mentioned buying the Hughes bushing/spacer!!! Its cheaper then the flexplate at just 45 bucks then elongate the holes in stock flexplate alittle! . No bolts needed it rides in the crank hub. It sure beats paying $185 just to bolt up a transmission!!!

 

Ok, Bo185, I know you're here and also on pirate. I'm working a swap and picking up pieces here and there. I know it's best to get a gen 3 trans, but I don't have one and don't want to buy one since I already have a fresh 94 era 4l60e. This is a non-pwm trans with the 4 bolt tailhousing. My engine is ~01 5.3 and will be DBC. There is a stack of PCM's I'm going to pick through to find one I need. Is this workable or am I going to be forced into getting a PWM trans?

A, FWIW, I'm not concerned with the mounting, just the electronics of it.

 

OK....I have a 2004 6.0(short crank version) I have the TCI aftermarket flat flex plate #399753. I will be bolting up a TH350 with a TH350 convertor.

What if I remove the factory crank spacer. Then I bolt the flat flexplate to the crank and use the hughes spacer between the flexplate and the convertor? Will the starter still engage correctly given that the flexplate is so much closer to the block?

Or is it mandatory that the factory crank spacer is used between the crank and flat flexplate?

In other words... I understand that the spacer is needed on one side or the other for the convertor to seat properly....BUT does it matter to the crank(internals) or starter if the flat flexplate is close to the block or far away? Being that it came from the factory with the spacer between the crank and flexplate.

 

You should be able to just tune the PWM out of the PCM and be fine. The 94 will have oneless pin in the trans connector as well. I would contact your tuner and ask to make sure before committing 100% to cover your bases though.

 

I can't speak for a TCI product as to whats need, you may contact them. But I would assume it wouldn't need any spacer as it was made to work with the TH350 but contact them to be for sure.

No I can say the GM flat flex plate needs the spacer next the the crank. reason being the flex plate is flat and its the only place it can go. If placed the other way with the spacer after the flex plate. the flex plate is no placed.

The spacer supports the converter hub and that's it. The starter engagement alignment is based in part on the shape of the flex plate IE dished or flat for a given application.

I assume GM did as they had the tooling for the old 4l80 converters and because they had a carry over of 4l80 with 350 applications for several years. At least till 2002 GM still used the L31 350 in the full size van with a 4l80e. After the Gen III introduction in the trucks in 1999 GM still needed a Gen I and Gen III application so it was easier to have the shorter hub Gen I application hub that would fit both applications. As its cheaper to make the spacer vs two different conveters.

 

Well, I asked a GTP tuner guy at work if he had any ideas and he didn't. But he did send a message to a guy who does a lot of LS tunes and specifically tranny stuff and he told us that there's something about disabling the PWM that freaks the PCM out and it just won't work, at least for now.

So, now I'm on the hunt for a 96-03ish 4l60e. Have a lead on a $30 core and I think I'm just going to take the guts out of my trans and stuff them in this one.

Thanks for your input, Bo.