strange 1st-2nd shift

[coker6303]

I've been running Rob's 110hp tune on my LMM. Changed from a 70-80hp tune to Robs 110 and did the relearn. light and medium throttle shifts are spot on. Clicks through the gears perfectly. The weird part is at wide open throttle. If you roll along about 5mph and hit WOT the truck will go to shift into second and shut down. Feels like it makes the shift but drops all power, let off and get on it again and it takes off as if nothing happened. No codes. pulls great through 2nd, feels strange in 3rd (feels like you loose some accelleration and may be revving a little high) and then hits 4th perfectly and pulls hard again. Can't tell you about 5th and 6th, I don't pound it shifting into those gears. The TCM has not been changed, all stock shift points.

The only current mod to the tranny is the transgo jr kit. What do I need to be looking at in the ECM or TCM to get these shifts a little better? Any advice is appreciated.

Russ

 

[Bako_Dmax]

I think your experiencing the truck defueling between shifts, which is saving your trans from slipping.

 

[Mike L.]

I think your experiencing the truck defueling between shifts, which is saving your trans from slipping.

I totaly agree. Problem is; it still does a lot of damage to C3's even with the engine shut down. Need more trans.

 

[coker6303]

I totaly agree. Problem is; it still does a lot of damage to C3's even with the engine shut down. Need more trans.

one of these days Mike!! LOL

When it shuts down shifting from 1st to 2nd, I have yet to keep my foot on the floor. I let out and then get back in it. Guess I need to stay in it just to make sure it is the defuel....or we'll be building a tranny sooner than expected!!

 

[The Neens]

one of these days Mike!! LOL

When it shuts down shifting from 1st to 2nd, I have yet to keep my foot on the floor. I let out and then get back in it. Guess I need to stay in it just to make sure it is the defuel....or we'll be building a tranny sooner than expected!!:D

I totally agree

 

[dwax]

mine did the same thing (exactly) the first time i tune it with efi. turns out my old ppe was still hung in my computer somehow, so i reflashed the ecm, tuned it again, and then it shifted great... at the time my only tranny upgrades were transgo and T.C.

 

[coker6303]

mine did the same thing (exactly) the first time i tune it with efi. turns out my old ppe was still hung in my computer somehow, so i reflashed the ecm, tuned it again, and then it shifted great... at the time my only tranny upgrades were transgo and T.C.

I have flashed it 3 times with the same program to be sure that everything is right. Might do it again just for grins. :thumb:

Aren't the defuels in the TCM? That would mean the truck should still have the same defuel as before since I did not change the TCM tune right? All I did was pull 1 EFILive tune off the ECU and replace it with Rob's tune.

 

[SteveFord]

Possible torque managment kicking in. I wouldn't worry about it until you get your trans upgraded.

 

[Mike L.]

Defuel is ECM.

 

[The Neens]

I'd give Rob a call, I'm sure he can make an adjustment to help you out...The 1st "big" tune I put in my LBZ acted this way, until it got some tweaking...

 

[x MadMAX DIESEL]

Are you hammmering down in Track/Haul ass mode? or just in overdrive? I'm gueing your TCm has got used to shifting in O/D if taht's the case it will take a bit to figure out the shift point's to shift in/.Most people put it inTH mode to hammer downa nmd only use that switch for getiin on it it

 

[coker6303]

I'll give Rob a ring this evening and pick his brain.

On the bright side, Rob's 110hp tune is friggin amazing! Very friendly around town and in traffic, very responsive but not explosive until WOT. Beats the crap out of my 80hp tune I was running before. :thumb:

 

[coker6303]

UPDATE

IdahoRob fixed the problem, just a slight change in the tune fixed everything up. Shifts spot on!

Here's a mechanical problem that is developing. After I let the truck sit with the engine off for a couple of hours during the day or overnight (and I let my truck idle before driving) the light-mid shifts are drawn out. The engine revs a couple hundred rpms between shifts instead of snapping to the next gear like it should. It goes away after it is driven for a mile or so.

Here's the best I can explain it: apply light throttle revving to 2200rpms and the shift from 1-2 is triggered, the engine free revs (no trans resistance) an additional 200rpms to 2400 before pulling down into 2nd gear. It will do this whether you are in tow haul or normal. TCM tune is stock.

Again, it only seems to do this after the truck has set for a while. I'm going change the tranmission fluid again (changed 12000 miles ago with Amsoil). Truck has 37000 miles on it.

 

[coker6303]

logged 4 passes at WOT, during 3rd gear the revs are around 3400 rpms and trans slip rpms are up to 800. Remaining at WOT, it has no problem shifting and locking the converter (+/- 8rpms) in 4th gear. 1-2nd shifts are great, but 2-3 and while in 3rd something strange is going on.

any ideas

 

[The Neens]

Did you log it from rolling into the throttle, or from a boosted launch?

 

[coker6303]

both rolling around 5mph and from a stand still, no boosted launches.

 

[The Neens]

both rolling around 5mph and from a stand still, no boosted launches.

When my '07 had a stock trans, boosted launches really exposed the 1-2 and 2-3 shifting problem...Rolling into the throttle, it seemed ok...Now, the ECM and TCM tunes have been modded, so it shifts well in any situation...

 

[coker6303]

i'm trying different tunes right now. I'm at a loss, confused trying to figure this out.

I remember with the quadzilla tunes boosted launches shifted great, it was the mid throttle shifts that were odd.

 

[coker6303]

alright, now with the quadzilla 90hp tune it is going to the rev limiter in 1st and shifting, bounching off the rev limiter in 2nd before shiting into 3rd but the converter is lockingup in 3rd again.

Is it possible I am getting a bad VSS reading at the transmission? I can't get my MPH to register when I am logging the TCM.

 

[The Neens]

Load your 70-80 HP tune and try it again...