Few questions on my 1st LT1 tune

[kur4o]

With 3500 rpm stall torque converter, upshifts doesn`t work because of the stall wall.
It`s known problem with the lt1 pcm.
Do some google search how to fix that and post the working formula.

Transmission is different between 94 and 95 and you shouldn`t mix bins.

[JustinSEO]

With 3500 rpm stall torque converter, upshifts doesn`t work because of the stall wall.
It`s known problem with the lt1 pcm.
Do some google search how to fix that and post the working formula.

Transmission is different between 94 and 95 and you shouldn`t mix bins.

That is what I was thinking, the stall definitely has a part to play in that. I will do some checking, and probably talk with Keith of PCMFORLESS to see what they do for large stalls like that if he'll share!

I didn't mix the bins, I wanted to copy values over but it is not necessary now that I have a stock 94 bin that is up-to-date... I don't think I have ever clenched my cheeks so tight while watching that flash; haha.

[lionelhutz]

I thought it was that the VSS code would get set with a higher stall?

You should be able to enter low mph upshift settings into the kickdown tables and then use the rpm table to select the shift point. I've never read anything that says you can't tune for the converter, just that the car won't shift with a bigger stall when it's a stock tune.

I had to fix my PCM in the fall. I tried to change a table in Tunercat while flashing - don't do this....

[JustinSEO]

I thought it was that the VSS code would get set with a higher stall?

You should be able to enter low mph upshift settings into the kickdown tables and then use the rpm table to select the shift point. I've never read anything that says you can't tune for the converter, just that the car won't shift with a bigger stall when it's a stock tune.

I had to fix my PCM in the fall. I tried to change a table in Tunercat while flashing - don't do this....

Well I am unsure of how I would fix it, I am definitely not very handy with a soldering iron (haven't messed with them much though)...

This sounds like a good idea with the low MPH upshifts, but wouldn't it bother the cruising speed shifts? I am gonna try to up that VSS diagnostic enable to 4,000 RPM and see how that helps me out. I haven't ever seen the "limp mode" where it will only stay in 2nd and 3rd; but I definitely see it hitting the rev limiter on upshifts on occasion and sometimes the car downshifts right into redline requiring an upshift right after!!

I do not plan on changing any pressure or shift times really because I cannot afford to rebuild a trans right now; I already have a shift kit and it shifts pretty good... smooth and still "strong". I'd rather keep it safe.. I would like to see WOT up/down shifts be tuned out; I guess it is just trial and error, gotta get a spare PCM and mess with it.

[sherlock9c1]

The problem with bricked LT1 pcms is that it's cheaper to get another one out of a junkyard than it is to try to fix it. You've gotta unsolder a tiny chip, flash it with a chip flasher ($100 or so), then reconnect it onto the board, either soldering or soldering a socket on the board and then putting the chip in there in case you get another write failure. there are two memory chips on the 8051 boards; usually I've only seen one fail (it switches over at 50% loaded, which is why it hangs for a few seconds then continues loading).

[JustinSEO]

Well I guess I will just scrap my spare and get another... Sounds like to much work to fix them. I thought I heard of a guy fixing them for cheap though....

Any other tips for the tune? I would like to have a dyno tune but nobody tunes lt1 cars around here... I want to add some timing and get my AFR corrected to make some more power and take advantage of the CAi and cat back... Obviously the stall and trans need a tune badly

[lionelhutz]

I don't know of anyone that fixes them now. There were a few people that used to do it but they quit, likely because there wasn't much demand. If you're interested in selling it I might fix it myself and keep it for a spare. I only have the parts to fix 1 more.

First thing I'd do with the transmission is drop 10 or 15 mph from the kickdown mode table. Then, drop the rpm in the rpm table to around 5000rpm. Try it and see where it shifts. Then adjust the rpm table until it shifts where you want the shift. Log it and pick out the speed and rpm you get right when it shifts. You can use the speeds in the main shift table so the kickdown and main speed tables blend as you transition to WOT.