More stuff on swapping a 4L60e for a 4L80e

[Doug Bazarnic]

I've got my tranny rebuilt and installed by around 3 o'clock Sunday
afternoon.  $298 in parts and about a day and a half labor.   What a pain
in the butt! 


>>The main electrical connector that interconnects the engine wiring harness
>>to the transmission is not the same and there are different numbers of wires
>>used (I don't know what they are all used for).

After reading the service manual, the main electrical connector on both
trannys is the same.  However, the 4L60E has 2 more wires than the 4L80E.
(The connector has lots of empty pin holes)   The 4L80E also has a
secondary speed sensor unit, which would require running two wires up to
the computer, that my wiring harness doesn't have.


>>There are two different PCM's that control the 4L80E. One comes on the
>>diesel engines and the other for the gas engines. 
>
>Yes, and there is a third PCM for turbo diesels, too! Each is (totally)
>different and not interchangable. As well, there are two (at least) 4L80E
>transmissions, the early and the late models. The TCM/PCM is different for
>each, so that makes about five different TCM/PCM combinations! 

That was my next question.   After comparing pinouts on the 4L80E equipped
computer vs my 4L60E equppied computer,  the 4L80E has perhaps 2 wires
different, and the addition of 2 more, where my harness has "empty" spots
on the connector.  So, are the computers really different, or do they just
not hook up the wires that would go to it?   I know the calpak would be
different, and perhaps that's the only difference?!?   Would they really
make different computers for such a slight change and not enable/disable
via sw?


>>The 4L80E uses a different flywheel and torque converter. I'm not sure

>>whether the crankshaft end would need to be reworked to mate to the 4L80E.

The 4L80E would require a different torque converter from my 4L60E, but
that's not a problem, as I don't use the stock converter anyway and would
buy a higher stall after market unit.    The flexplate is engine dependent
and not tranny dependent.   I'm not running the one piece real seal
crank/block anyway, but a gorgeous Cola Crank with a 4 bolt splayed cap block.

>>The transmissions are different lengths which would necessitate a change of
>>your drive shaft.
>
>And probably rear mounting bracket, too.

The hardware to mount the tranny is of little concern as I consider that
the easy part.   I'm just worried about the computer crap.   Mainly because
I've gone thru about 150 eprom burns to get my engine dialed in to my liking.


>>I have read of people that have done the swap successfully, so with enough
>>knowledge, time, and money, you can have a 4L80E which is a much stronger
>>transmission. And I would guess that it would ultimately be cheaper for you
>>to swap out to a 4L80E transmission rather than to keep paying for a
>>transmission rebuild every so often.

I would rather have beefy parts, rather than one that lasts a year.   I
found my old receipts and the last tranny build I had to do was on April
4th.  Almost 1 year.   If  you guys would like me to take some pictures of
the parts that failed, and the clutch size differences, I think you'd be
amazed at what a piece of crap the 4L60e is.   The 4L60e should NOT be in a
1/2 ton truck -- maybe a S10 or camaro, but defintely not in something heavy.

As far as the costs for rebuild, all I have to pay for are the parts, as I
do the rebuilds myself.  (Which is both good and bad sometimes -- good on
the wallet, bad as a pain in my ass! :)

>I'm sure a swap is a good idea. I'd contact JET and see what they have for
>kits--they sell a complete kit, TCM, 4L80E, harness, etc. Might be just the
>trick to get you going.

I'm not sure how I could fool my stock computer into thinking there's no
tranny hooked up if I were to use an aftermarket kit.

If I have to buy a new computer, I'd assume I'd want one for a '95 with a
350 and a 4L80e.  My current chip code was BJYM.   I have massive changes
to the engine management part that I'd hate to do over.  So, is it possible
to copy the engine calibration stuff over to a new chip via a range of
eprom addresses,  and merge it with the tranny stuff?

Some people have asked my for my BJYM code, and I'd be more than happy to
share it.  I can also post my current code that I'm running with my engine
setup.    I've done all my mods thru MasterTune software that's supposedly
specific to my chip, so I don't know how/what/where to modify stuff in hex
for different chips.  

Is there a master list somewhere that somone has compiled with hex
addresses so I know where to put stuff?   Also, when I've tried editing in
the past, the chip wont run as I don't know how to compute the checksum --
so I loaded my hex edited file in MasterTune and resaved it and it computed
the checksum for me.

   If anybody knows how to "hack"  MasterTune to see if it will really do
all chips or what, I'd sure appreciate it.   The software is in two parts,
engine and tranny.  Before the sw can be used to look at your chip, you
must first put a "secret" code into your .bin file, as well as know the
secret 4 digit password, which makes for a pain in the ass when you haven't
used the sw in 6 months.

Finding the original BJYM code will be a task, but I can upload my current
config asap -- just tell me where.  Also, not sure if I should post the
MasterTune sw or not?  (good/bad?)  I paid nearly $600 for it, and if
someone could help modify it so it will do 4L80e stuff, I'd be more than
happy to upload it.

Thanks for all your help,

Doug Bazarnic