anyone changed the speedo revs/mile on an 09?

[camcojb]

A friend bought a new 09 4WD CC 1-ton dually and had a different set of tires he wanted to run, so I changed the revs/mile in the ecm tune (8594 OS). Now when towing it seems to lock/un-lock the converter in fifth gear (60-62 mph), worse when going up a slight incline. He's in tow/haul, at about 1750 rpms and then jumps to 2250 rpms, then back, and so on. The rpm jump is not enough to be a downshift to fourth gear so I'm guessing it's the converter. It does it in tow/haul and regular mode, but it'd be in sixth gear when it does it in regular mode, not in tow/haul.

It started immediately after I changed the revs/mile. The 09 tcm's are not tuneable yet through EFI Live, so it may be that the revs per mile change in the ecm is confusing the tcm. I have switched just the ecm revs before on other older 6 speed trucks and never had this issue. I also shut off the egr, otherwise I made no tuning changes, the truck is still completely stock with dpf, etc. I don't see how shutting off the egr could do this, but it's possible. I tuned another 09 for a friend and shut his egr off also, and his is fine, no issues. We did not change the speedo though.

We'll put it back when he can get the truck back to my area, just wondered if anyone else had this issue with an 09.

Jody

[rcr1978]

I have not touched a 09 but my 07.5 does exactly what your describing and revs per mile are stock, this is why I have always asked for more pids to log whats going on with the convertor. I have noticed this on other LMM's that are bone stock also, maybe yours is tuning related who knows but I was under the impression that all LMM's did this it's weird to it sounds like the damn thing is slippin bad I see up to 175rpm of slip when it does this.

[camcojb]

I have not touched a 09 but my 07.5 does exactly what your describing and revs per mile are stock, this is why I have always asked for more pids to log whats going on with the convertor. I have noticed this on other LMM's that are bone stock also, maybe yours is tuning related who knows but I was under the impression that all LMM's did this it's weird to it sounds like the damn thing is slippin bad I see up to 175rpm of slip when it does this.

this truck had not done it until I changed the revs/mile. Tune is stock, other than egr off. This one has a 500 rpm difference at 62 mph or so, but it was towing a 50+ ft trailer with cars inside.

I had him shift from 5th (1750 rpms) to 4th to make sure it wasn't downshifting; that changed rpms from 1750 to 2500 rpms. In 5th gear it's going from 1750 to 2200-2250 rpms or so, so it's not downshifting.

[rcr1978]

Weird, post your results when you go back to stock.

[camcojb]

okay, got the truck back today. He pulls 10-15K pounds constantly with the truck. First, went for a drive and under moderate to heavy acceleration the truck makes these split-second wheezing sounds, engine related in my opinion. So we pulled over and I turned the egr back on, problem gone.

Next, when towing in tow/haul down the freeway, even on flat ground it will downshift and upshift from 6th to 5th and back. Definitely not the converter un-locking. Seems normal to do it on hills, but it does it constantly on flat ground.

Put the stock tire revs back in, problem is gone. Put the tow tune back in and problem is still gone, actually better because now we could climb smaller hills without downshifting, where even the stock tune would............ more power. But with the tow tune and revs changed the downshift problem came back. If you turn tow/haul off it will not downshift, but it locks/unlocks the converter which is almost unnoticeable. But since he tows and wants the higher upshift speeds and decel braking that gives, he settled on the tow tune, egr on, and stock tire revs.

We kept making the same exact freeway loop and the same speed so we could see if the changes affected anything. It was a mostly flat section with a couple small hills.

He's going to have the dealer flash the truck, both ecm and tcm to see if with them matched the downshift/upshift on level ground goes away. If it does I'll put the tow tune back in and he should be set.

It seems the tcm on the 09's has something that causes an issue when you change the ecm revs without changing the tcm revs. We can't access the 09 tcms yet, so no choice there. Without the trailer (load) the rev change worked great, but under towing heavy it is an issue. I also don't know why turning off the egr made that engine sound from time to time (again only when towing and the load went up), as I have done that to other 09's with the same OS, but they do not tow heavy.

Jody

[09LMM]

I have changed the revs/mile and there have been no adverse effects.

I have also tried turning the egr off, this did cause strange behavior. I did hear the stange wheezing sound and sometimes a loud pop coming from the exhaust (i think). there was also an intermittent dead spot during hard acceleration - this was dangerous if crossing a busy road, hit the throttle and nothing for a split second, then it would take off. Needless to say i turned the egr back on. I would like to know if anyone has found a solution to this problem.

One other thing that I have considered, is that when I tried turning off the egr there was still a DPF in place, and I think the regen1 cycle uses the egr in its operation. I am going to try turning off the egr again now that i am DPF free.

[Sparky8370]

I would say that you need to adjust the shift points as well, but obviously you can not do that because you can't get into the tcm.

[09LMM]

One thing that I did forget to mention in my last post was that it took about a week of driving after the revs/mile change before the shift points adapted the torque difference. At the very begining it seemed like the transmission would always shift up to too high of a gear and lug the engine down to around 1200 rpm or lower, after a week of operation it seems to maintain 1500rpm and above(not in tow/haul mode). I'm not hauling a trailer at this point but do have approx. 2000lbs in the box at all times. I went from 30.5" tires to 33.4" tires.

After the DPF fell off it seemed to take a week as well for the engine ECM to adapt to the change.

I'm not quite sure if all this is in my head or not, I haven't data logged anything as of yet.