Help with 80E shift points

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May 14th, 2008
thunder550

Help with 80E shift points

Ok I've been battling this issue for a long time. I have a Silverado 1/2 ton with a swapped in 80E, vacuum modulated.

I want my WOT shift points to all be right about 5700 RPM. To make the tranny shift there on a WOT run from a stop I set all of the WOT shift tables at 5000 RPM. I have the 1-2 WOT shift set at 55 mph, 2-3 at 88 mph, and 3-4 at 256 (not that it matters).

When running from a dead stop through the gears, it shifts correctly right around 5700. However, if I go WOT when I'm already rolling at something like 50-60 mph, it will drop down a gear or two and start pulling from something like 5000-5300. In these cases, it will run to almost 6500 RPM before the shift.

I have heard from several different people that are having WOT shift point issues with their 80E trannies. Does anyone have a solution to this? I tried zeroing out the WOT shift speeds but then the trans goes 2-1-2-1 when I go WOT from a cruising speed of around 40 mph. I'm out of ideas.
May 18th, 2008
thunder550

Anybody?
May 19th, 2008
SRT10KLLR

Can you post up your tune and log.
May 19th, 2008
joecar

Yes, post up your tune.

The VM only modulates line pressure (not used for torque signal shift control)

I can only think of these things:
- your throttle position sensor is failed or intermittent,
- your WOT enter/exit threshold are crossed,
- your kickdown tables are not at TP 100%,

Hmmm...?
May 19th, 2008
thunder550

2 Attachment(s)

Tune and log attached.

The log is large, but take a look starting around frame 22832, I got WOT and the motor downshifts into 1st from 43 mph and runs to almost 6500 before the 1-2 shift.
May 19th, 2008
joecar

1 Attachment(s)

I made some changes, try this...
May 19th, 2008
thunder550

Hey thanks for the help. My truck has no engine at the moment, but as soon as it's running again I'll give it a shot :hihi:

I see the changes that you made, what do you think the problem was?
May 20th, 2008
joecar

I'm not 100% sure... the difference between the up/down MPH's seemed too close, and the kickdown tables may overriding the other tables/parameters... but I'm not 100% sure... when you get your motor give it a try and we'll see from there.
May 20th, 2008
thunder550

Ok, I'll let you know when it's back on the road again.
May 20th, 2008
dc_justin

Quote:

Originally Posted by thunder550

Hey thanks for the help. My truck has no engine at the moment, but as soon as it's running again I'll give it a shot :hihi:

I see the changes that you made, what do you think the problem was?

Kickdown could be causing the TCC to slip a bit more than it would running up from a dig... Just a thought.