4L80E shift issue info to share

[millsroger]

OK-the issues first--Select first, you get first and second. Select second, you get first and second. Only thing that changes is the 1-2 shift point.

Not all of you may think of this as an issue but I do. I learned along time ago that starting on snow or ice is often better done in second gear due to the reduced torque. No such thing with this tranny. Also, off road if I want first gear I don't want it slamming into second.

One other issue is the TCC in normal drive. Some of the hills I need to pull loaded down with water tanks will not pull in fourth. Shifting to drive keeps it from trying, but, the TCC is still kicking in and out. This is heavy throttle and makes me worry about the TCC clutch.

Have read the posts on toggle switch overrides, and read up on various manual shift kits. None are a good solution and some confuse the ECM and throw error codes.

Well, I since I had been in conversation with SS re a chip any way, and the TCM and ECM use the same PROM, I inquired about changing the transmission table. Answer I got was "we can do that with no codes". Same price, just have to ask.

So, here is the way the tranny would work--first is only first, second is only second, Drive has no TCC, Overdrive is normal. They can also back down the part throttle shift points when in Low Range so it isn't as harsh.

The game plan is those changes to the TCM portion of the chip, ECM portion per their 'mild' upgrade and the small Transgo kit that has the pressure regulators but not the reprogramed shifts.

Any comments or observations are welcome and better now than later.

 

[ak diesel driver]

I'd want the TCC to lock in drive but with alot more throttle required to unlock.

 

[millsroger]

That would be OK, except I would want TCC unlock long before kickdown. Same for OD. And no mid throttle hunt.

 

[WarWagon]

My 1993 will go into TCC lock in 3rd after 30 seconds or longer at WOT. I think this is to keep trans temps down as running the TCC unlocked at WOT for a long time will heat things up quick. I have not had any TCC hunting on hard pulls but then the throttle doesn't move off the floor.

I would pull the converter out and put in one with a better TCC clutch in it than stock. The stock ones are good for about 50K of hard pulling with an override switch. Before they slip bad enough to throw a code anyway. The TCC override switch and compression braking is a bad idea in 2nd. The 2nd gear manual overrun clutch is small and is easily burned out even with a shift kit. AKA do not lock the converter when compression braking. Brakes are easier to change than a trans rebuild.

 

[millsroger]

War, Do you pull at 50K often?? Here is the max numbers per GM for 93-9x

Max gross weight shown for any model 10,334 (combined f/r)
Max ball tow Combined truck and trailer 19,000 DRW
Max 5th wheel weight 12,500 DRW, (standard hitch weight ratio)

That's no where near 50k, no wonder your TCC burns out.

 

[tanman_2006]

I think he means they will last 50K miles before burning up in his towing conditions.

I had buddy set my 95's tranny tables up because it hunted while driving and turned out to be the TCC valve is worn (in the valve body IIRC). Somehow he fixed this in the programming because I have to try to make it hunt now.

 

[THEFERMANATOR]

I think he means they will last 50K miles before burning up in his towing conditions.

I had buddy set my 95's tranny tables up because it hunted while driving and turned out to be the TCC valve is worn (in the valve body IIRC). Somehow he fixed this in the programming because I have to try to make it hunt now.

It's not a fix, but more like a pressure over ride if it's what I'm thinking he did. And it is probably the AFL circuit in your valve body that is giving problems as it regulates the fluid pressure that the valve body uses for the shift valves.

 

[millsroger]

Apologies to War, I mis-understood.

Ok, so the hunting is a worn valve with the AFL circuit trying to compensate???

So, question, can the valve be replace without pulling the trans? Does the Transgo HD-2 kit fix this??? Was thinking about just the SK kit but the HD has the dual feed direct clutch stuff AND the over pressure stuff.

 

[THEFERMANATOR]

The AFL is the actuator feed limit valve, and yes it can be repaired by dropping the valve body BUT you do have to buy a reamer and a seperate kit from a shift kit to install it. When it gets worn you get fluctuating fluid pressure in the control circuit of the valve body which causes the valves in it to not fully engage. You can raise the line pressure and flatten it out some which helps to band aid teh worn valve by putting more line pressure on tap so that when it fluctuates the low is high enough to keep it from slipping. The downside is the high of the fluctuation can break input drums.

 

[millsroger]

Thanks Ferm, preventing over pressure is why I was looking at the Transgo kit. With 250k mine is prolly worn as it does hunt. Would need to pull the valve body anyway so I would also look for the repair kit.