trans not shifting propely

[lb7/76camaro]

hey, I have a lb7/allison in a 76 camaro. Put a decent tune to it and now won't shift. Its strictly drag, and wondering if just programming can take care of this issue?

[joecar]

I don't know anything about Allison's...

but do post your before/after tune files, and any log files, so someone can take a look.

:)

[LBZoom]

Is it hanging up on the shift, or just shifting hard, or do the RPM's jump on the shift? It could be the gear ratio... what ratio are you running? The stock allison is programmed with 4.10, even though the Dmax trucks actually run a 3.73

[2001-GMC-LB7]

Did you reprogram the trans as well?
Did it work before the updated tune was installed?
If so, probably a tune error.
Can you post the tune???

[lb7/76camaro]

Just the engine trans did work good before. The tune was from the place I bought the programmer so should be no problem, but possible. Some reason the website won't let me post the program will try again later. Did have it out past sunday and changed the diff ratio helped but seems like its just missing the gears then enguaging. Ran a 12.29 with i think a governor still on cause it falls on its face at the top of the track.

[LBZoom]

Just the engine trans did work good before. The tune was from the place I bought the programmer so should be no problem, but possible. Some reason the website won't let me post the program will try again later. Did have it out past sunday and changed the diff ratio helped but seems like its just missing the gears then enguaging. Ran a 12.29 with i think a governor still on cause it falls on its face at the top of the track.

Sounds like it's just de-fueling, check you base torque tables and see if they are still stock... if so raise them up in increments and see if that helps, the base torque table is responsible for the de-fuel effect. As far as why it fell on it's face, could be a rev limiter but sounds more like some other limiter, I'll wait to see the log before I make a suggestion there.

[THEFERMANATOR]

Is it hanging up on the shift, or just shifting hard, or do the RPM's jump on the shift? It could be the gear ratio... what ratio are you running? The stock allison is programmed with 4.10, even though the Dmax trucks actually run a 3.73

The gear ratio settings in the TCM do not matter as to how it shifts. For some odd reason the GM engineers had all of the ALLISON TCM's programmed using the 4.10 ratio in them to calculate shift timing and such. When you change the gear ratio on the TCM you throw off ALL of the other tables along with it. And MOST of those tables CANNOT be seen by EFILIVE. When you change the gear ratio number you can also make it so the engine WILL hit the rev limiter before it shifts and cause it to fall on it's face. Most all of the big name tuners will tell you that the ECM is where you do most of your actual shift feel adjustments, and the only real changes to make to the TCM are shift point changes if your application calls for them.

[LBZoom]

I changed the gear ratio settings in my TCM and didn't notice any change whatsoever, on my 2006 LBZ, I adjusted the shift timing. On the LB7 and LLY trucks with the Bosch ECM the base torque tables will limit the de-fuel seperately from shift timing of course. I believe the base torque table is the single biggest player in shift feel... as for changing the gear ratio affecting the limiter... I disagree with that, as long as all tables in the ECM and TCM are set to the same ratio then all is well I'd say, if you set the rev limiter at 4,000 RPM's it's still going to hit 4,000 RPM's especially if you haven't physically changed the gears. You're more likely to fall face first from hitting an underboost code or MAF code in my opinion.

[lb7/76camaro]

Well every run I make its went 105mph no matter how it shifts or leaves the line. I changed the diff ratio to see if it would change anything, I gained 2mph and .2 of a sec. By changing the diff ratio I was just seeing if it would gain speed by having it think it was going the same speed but reving higher. Also I think its a speed limiter not a rev limiter. When you adjust the torque table how would you do it to help shift better and not take away to much?

[LBZoom]

Well at full throttle you can probably max the base torque table out and get a good firm shift and not lose much on account of de-fuel because it's not going to cut you back as much. As far as for part throttle, you'll have to adjust in increments until you get the desired amount of de-fuel, personally I like a small amount of de-fuel for a more solid feel and smoother feeling shift. There is also speed limiter tables in the ECM under the speedometer segment, and I believe there are some in the TCM also but I can't remember for sure without looking.

[lb7/76camaro]

K, will see what we can do and let you know how it works. The file for the trans on the other thread is just the stock one if you think you need to look at something else let me know.

[Nmband13]

there is a stock 110mph speed limiter in the ecm tune. have u changed that?

[horsehaulin]

Email me both tunes. I will try to help you as best as I can.

I also need to know tire size. Please send the stock trans tune, not your modified one. And who is the tuner/seller of the EFI Live?

Armdist@yahoo.com

[lb7/76camaro]

Tried modifing the trans, didn't work so I put it back to normal and it started to work better. What I did, don't know but I found under Main Injection the problem of the power fall off. It had the fuel to speed set at 0 after 161kms, so I just kept the same numbers going through the table, and ran a 112mph, short times couldn't get right though. Fell of even with the 112mph ran a 12.55. Had to lift, so should have been better. Can't get loaded up at the line enough to get consistant runs, will figure out something.