I had my 4L60E rebuilt by a reputable local shop per suggestion of the shop doing the R&R, heads and tuning.
I first got it back it was supposed to be tuned for maf. The tuner is said to have good knowledge of the 98 pcm.
It had surge and idle issues. The shop retuned it. Unknown to me it was tuned SD.

I was told by another person that 98's with an SD tune will kill a 4L60E.

After all the work and tuning, the trans lasted 700 ish miles with 2 track passes. The shop warrantied the transmission with a different core. It kasted 300 ish miles.

 

and this is EXACTLY why my shop refuses to sell to F-body owners.... The shop that built the trans originally is NOT at fault here-but now you have cost that shop another full build, and them providing a core, parts and labor. I hope that shop is smart enough to figure out what the real problem is and to just walk away from you as a customer. What you/your tuner are doing/have done is NOT THEIR FAULT NOR SHOULD IT BE THEIR FINANCIAL RESPONSIBILITY. Unless you told the trans shop up front that the tune had been hacked by another shop, you did not give him all the information he needed to make an informed decision... The other way to look at it would be to say that the trans shop owner failed to ask the correct questions and now his failure to properly vet his customers has cost HIM a bunch of money, drama, heartache, and stress.

Your 4L60E uses the MAF sensor signal to control line pressure inside the transmission. Without that MAF signal being available to the PCM it's going to be difficult to keep the trans from burning up the 3rd and 4th clutch pack.

Don't forget that even with a "built" trans, you WILL STILL need to match the gears in the rear differential to your tire size-think higher numeric gears to give the transmission a chance at survival. You will also need to match the stall speed of the torque converter to the cam-and also to give the engine a chance to rev and increase transmission pump speed which will help build pressure and volume to again, help keep the transmission alive. You will also need a BIG external cooler. The factory trans cooler inside the engine radiator is barely suited for an all stock transmission. If you have done anything to increase horsepower, or torque, or added a higher stall converter, it is mandatory that you install a BIG external cooler to deal with the extra heat. Lastly... the tune... It is life or death for the transmission. Even if you get everything else in the "system" set up correctly, a tune that is not 1000% right is going to fry the transmission. No way around it. I'd say you have a $5000 repair bill ahead of you to get everything set up correctly and have a complete "system". If you don't have the money to do it RIGHT.. how will you find the money to do it TWICE, or three times, or......? $5000 might be a low estimate.. but hopefully you get the point.

Good luck with your project.

 

No, that is ridiculous. If the tune isn't setup properly than sure that can happen but that's not specific to the 98 PCM and can happen with P01/P59s as well. The older LS1 computers don't have the best direct control over the torque model which is what it uses to determine the delivered torque value, BUT you have plenty of control over the line pressure that is commanded at a given torque value. As long as the tuner is paying attention to the delivered torque value and line pressure than it's not a problem... and it has nothing do with it being tuned in speed density vs using a MAF.

 

You have a lot of assumptions and take me for a noob and not really answering the question. Instead come off as jerk.
The other core did not come from the trans shop.
Yes I have a large external oil cooler for the trans.
Yes it has a stall, cam, heads and gears.

The trans was warrantied because the shop that did the r&r also handled the tuning. So as to why they warrantied it wasn't on me. I didn't deal with them.
So yeah I'm out the money for all the work done you think it's the tune?
I'm just trying to figure out why it happened.

 

I ran a '98 PCM with a 4L60E in SD mode for at least a few years with dozens of track passes without problems. Granted it was a brand new 4L70E which I retrofitted to work as a 2006 4L60E and installed the Transgo Shift Kit; I even turned off torque management. It run thousands of hard miles. When I finally pulled the trans, it was still working perfectly; I rebuilt it with many internal performance parts.
Now if you had HP Tuners we would ask to see both the tune and a log of things like MAP, TPS and most importantly the transmission's PCS current.
The MAP and TPS should be enough for the PCM to determine the load and reflect this by lowering the PCS current to increase line pressure.