"Limp mode" hesitation on an 8.1 BB

[06MonteSS]

try this... if this doesn't help at all, I dunno what's going on with your truck man... as far as the custom tunes that we have even tried before, I did the same things to yours that I've done for other 8.1L / allison tranny guys I've done tunes for, and they didn't have any issues....

so, see what this one does...

which tune did you have installed in the truck, the diablo 87 tune?? this new custom file is a copy of your last tune written file, but with the tranny settings put back to stock settings...

and yeah, I checked out your log... very odd... your timing keeps going negative, at one point as much as -10... I'm guessing that's the surging issue you're talking about that you feel... when the timing is going up and down.... it's going from like 30's and 40's, then BAM down to -x.xx for timing....

I don't know what that could be... will need to have mike and/or johan on this...

everything's good with the truck physically/mechanically, right?? plugs, wires, coils, etc etc...

[70Camaro406]

Thanks Lew. I'll give that a try.

Yeah, everything is good to go on the Suburban. The only thing that I thought that it could be early on was an oil pressure sensor that went out before the initial tune. I replaced it a couple months ago and there wasn't any change.

I actually thought about putting the TM back to factory and changing the shift firmness back to factory, too. Right now, I have the 87 tune, speedo changed for tire size, TM turned off, shift firmness on, and I bumped up the shift pressure and shortened the shift time slightly. Would that have any affect? It makes sense that it could, since whenever it goes into limp mode, it's right when it shifts into a gear... or, it starts out like that in 1st, then as soon as it shifts into 2nd, BAM, full power again. I'll download the new tune and load it up this evening. Thanks for hanging with this issue for me.

[06MonteSS]

you have an allison tranny right??

the shift parameters mess it up.. cuz the allison has it's own tcm module, that the diablo does not do anything with....

so to fix similar issues that others have had like you, putting the shift and tranny tm settings back to stock have fixed their issues... so, that's what I did in that tune....

let us know...

if it doesn't fix anything, then I am at a loss...

[mikel]

no, hes a 4L60E

[06MonteSS]

4L80-E...

so yeah, then I dunno man... maybe it's your torque converter???

[06MonteSS]

Hmmm....

"Solution to the 2nd to 3rd upshift problem (clutchpack engage-disengage-reengage)..." could be your surging issue, sounds like a common issue for that tranny??

go here, and it's video #10... http://wn.com/GM_4L80-E_transmission

[06MonteSS]

also, apparently there was some defect with the tranny... http://www.fullsizechevy.com/forum/gene ... efect.html

the link on that forum doesn't go to the article anymore, so not sure what the "defect" is....

[06MonteSS]

http://www.thetruckstop.us/forum/showth ... n-problems


only thing I can think of is there's a weak link in the tranny somewhere, so when the tune is installed and delivering more power/tq to the tranny, it's making the tranny problem rear its ugly head...

[70Camaro406]

Ok, I think I might have it straightened out. I couldn't get the revised tune that Lew did for me uploaded to my tool for some reason. It showed error 04000x. It uploaded 80-85% then the error came up. I think I didn't have the correct original backup tune matched to it, and I couldn't remember which one it was, since I have a bunch saved - even though they all should be the same...anyway. So I tried uploading the last tune written back into it and it went through.

I reinstalled the 87 tune, then reset all the parameters back to original. The only thing I changed this time was the tire size. I didn't touch the shift parameters at all or the TM. It seemed to drive like normal with a little extra power. When I pulled out on the highway, I layed into it and it still shifted hard under full throttle, which makes me think that there was some shift improvement already programmed into the 87 tune (which makes me think that I must have asked too much of the computer since I changed the shift time, pressure, and TM in addition to the 87 tune before). I only drove it last night - about 15 minutes on a 60 mph road, around town a little, and then though town and a 4-5 mile 45 mile road. Probably 18-20 miles and it ran fine and didn't have any quirks or limp mode issues, knock on wood. I'll keep you guys posted. Thanks again for all your help.

[mikel]

interesting, let us know.

[70Camaro406]

Hey guys. Sorry I've been away for a while. After my last post, I tried changing some of the parameters for the shifting... it still acted up. Since then, I installed a Magnaflow cat-back. Then a week later, I installed a set of Edelbrock headers (coated). Man does it sound different... Authoritative! lol Then, a week after that, I installed new plugs and Granatelli zero ohm wires. When I first got on the throttle after the header install, it spuddered some when it shifted into third (~65-70 mph). I thought it might be the plug wires since I broke one when I removed them to install the headers. The headers came with 2 new wires, so I replaced the broken one, but I must have hurt some of the others since it had a definite miss under load. That's when I got the new plugs and wires. There was 96k miles on it when I changed them. After the plug and wire change, it ran much smoother, but wouldn't you know it...the dreaded "limp retard" was still there.

It was getting close Christmas by then, and were were going to drive 880 miles the day after Christmas to visit the in-laws in the Suburban (4 kids, a dog, a roof topper, and it was still crowded!) I didn't want it to act up on the trip, so I took the 87 tune out and installed the original hp tune. I left the shifting stock, only changing the tire size and speed limiter. When I first fired it up, WOW did it idle smooth, and it actually revved in Park. With the 87 tune installed, it would never rev clean in Park, or Reverse for that matter. It always had a stutter. Even when I had to back it up in Reverse, it had that stutter (I don't know if I mentioned that before). Anyway, it drove like a brand new truck, had no hesitations or stutters from the "limp mode", and we drove a little over 2,000 miles that week. Now, I could tell it didn't have the extra hp that the tune gave it, but it was a relief knowing that it wasn't going to go into that limp mode on me when I least expected it, like pulling out in traffic, which it had done before with the 87 tune installed.

So evidently, the tunes that are in my tuner are not very compatible with my 8.1 L Suburban. I hate having paid $300 for a tuner only to use it as for the speedometer adjustment. Is there any way that you guys can compare my original hp tune file against both tunes that are installed in my tuner? Maybe there is some noticable difference in some of the parameters that's not letting my 8100 run right. I'm wondering if it's only set up for the LS motors and not for the 8100? I don't know what else it could be. I figure also that having the stock tune installed would help pin-point or rule out the problem, and it seems that it's in the Diablo tune.

If you need some sort of log file of the stock tune, or if you need me to download and post up the Diablo tunes, just let me know.

Thanks,

Wayne

[mikel]

post up the backup and last tune written again please...

[70Camaro406]

Well I figured I'd give this another go. I had lost the cables to my tuner for a while, but I just found them and figured I'd post up my backup and last tune written per Mike's request. The Sub has been running so good and smooth, I had almost forgotten that I still needed to get the Diablo tune sorted out. Our yearly truckpull is coming up in a few days too. I still have the stock tune with TM disabled installed. Here are both last tune written and original backup. Thanks.

BTW, just to refresh your memories, I have a 2004 Chevy Suburban 2500, 8.1, 4L80-e, Edelbrock headers, Magnaflow exhaust, Granitelli zero ohm plug wires, K&N, Predator 7193x

****
Lew,
If I decide to do the Diablew tune, is there anything different that I need to upload? Because I'm considering this route since the original tunes didn't work.
Thanks,
Wayne

[70Camaro406]

Wierd...my post didn't register when the new site converted... here is a repost of my last post a few days ago.

Well I figured I'd give this another go. I had lost the cables to my tuner for a while, but I just found them and figured I'd post up my backup and last tune written per Mike's request. The Sub has been running so good and smooth, I had almost forgotten that I still needed to get the Diablo tune sorted out. Our yearly truckpull is coming up in a few days too. I still have the stock tune with TM disabled installed. Here are both last tune written and original backup. Thanks.

BTW, just to refresh your memories, I have a 2004 Chevy Suburban 2500, 8.1, 4L80-e, Edelbrock headers, Magnaflow exhaust, Granitelli zero ohm plug wires, K&N, Predator 7193x

My uploaded files are in the previous post.

****
Lew,
If I decide to do the Diablew tune, is there anything different that I need to upload? Because I'm considering this route since the original tunes didn't work.
Thanks,
Wayne

[70Camaro406]

I see that my old tunes were downloaded. Has there been any progress made on them? Just checking in...

Thanks,
Wayne