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View Full Version : Help with 80E shift points


thunder550
May 14th, 2008, 08:50 AM
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.
thunder550
May 18th, 2008, 10:57 AM
Anybody?
SRT10KLLR
May 19th, 2008, 07:48 AM
Can you post up your tune and log.
joecar
May 19th, 2008, 07:59 AM
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...?
thunder550
May 19th, 2008, 11:47 AM
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.
joecar
May 19th, 2008, 01:50 PM
I made some changes, try this...
thunder550
May 19th, 2008, 03:55 PM
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?
joecar
May 20th, 2008, 02:54 AM
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.
thunder550
May 20th, 2008, 09:24 AM
Ok, I'll let you know when it's back on the road again.
dc_justin
May 20th, 2008, 02:08 PM
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.