The Shop Truck

[r3dd0g]

According to the Gearstar website:

• Billet Direct Drum with 36 Element Oversized Sprag with higher capacity frictions

So I'm just trying to understand exactly what you're talking about so I've snipped the 1-2 shift from my last run.

The red line is the gear that is being commanded by the dominator, the blue line is your gear ratio calculation. From the time it commands second until the gear ratio actually starts dropping from the 1st gear ratio of 2.48 is about 1 full second and after the dominator has commanded 3rd. You can see a little bump in the gear ratio line at the 2nd gear ratio of 1.48, but that's about 1.3 seconds after the command, then it drops to the 3rd gear ratio of 1.0.

What makes you think that it was actually in second and slipping while maintaining the 1st gear ratio? To me it seems like if it was actually in second and slipping the effective ratio would go up, not hold at the 1st gear ratio. I don't fully understand automatic transmissions, but to me it looks like it did finally hit second briefly, but took forever to get there. It looks like I'm having a pressure issue and it's just taking forever to apply the pressure to the 2nd gear, but maybe I'm misunderstanding how the transmission actually shifts.

As you mentioned, later in the run, it commands second again for a downshift, .8 seconds later the effective gear ratio starts raising and hits the 1.48 2nd gear ratio almost a full second later and holds until it drops back into 3rd, but it held in second for .5 seconds and the time from the 3rd command to the ratio drop was only .34 seconds and only .4 seconds until it was actually in 3rd again. I'm wondering if the pickup is sucking air and that's what's causing the delayed shifts and converter slipping. I really need that line pressure sensor. I may be able to fix this with a deeper pan, some baffles, or just adding an extra quart of fluid.

I need to go datalog a second gear pull, but that's really difficult in the middle of a big city. I wish I was still in Michigan with miles and miles of empty roads everywhere.
I did check my trans fluid on the first day, but never again after that.

 

[folkenheath]

According to the Gearstar website:

• Billet Direct Drum with 36 Element Oversized Sprag with higher capacity frictions

Yeah that one should be good.

So I'm just trying to understand exactly what you're talking about so I've snipped the 1-2 shift from my last run.
View attachment 534364
The red line is the gear that is being commanded by the dominator, the blue line is your gear ratio calculation. From the time it commands second until the gear ratio actually starts dropping from the 1st gear ratio of 2.48 is about 1 full second and after the dominator has commanded 3rd. You can see a little bump in the gear ratio line at the 2nd gear ratio of 1.48, but that's about 1.3 seconds after the command, then it drops to the 3rd gear ratio of 1.0.

What makes you think that it was actually in second and slipping while maintaining the 1st gear ratio? To me it seems like if it was actually in second and slipping the effective ratio would go up, not hold at the 1st gear ratio. I don't fully understand automatic transmissions, but to me it looks like it did finally hit second briefly, but took forever to get there. It looks like I'm having a pressure issue and it's just taking forever to apply the pressure to the 2nd gear, but maybe I'm misunderstanding how the transmission actually shifts.

Because it shouldn't take that long, something is wrong, whether it be low pressure or too slow of shift circuit I think something is wrong. I think the reason it commanded 3rd is because 2nd did not work. If second does not engage it will still be in 1st gear.

As you mentioned, later in the run, it commands second again for a downshift, .8 seconds later the effective gear ratio starts raising and hits the 1.48 2nd gear ratio almost a full second later and holds until it drops back into 3rd, but it held in second for .5 seconds and the time from the 3rd command to the ratio drop was only .34 seconds and only .4 seconds until it was actually in 3rd again. I'm wondering if the pickup is sucking air and that's what's causing the delayed shifts and converter slipping. I really need that line pressure sensor. I may be able to fix this with a deeper pan, some baffles, or just adding an extra quart of fluid.

Yes this is why I don't think it's your sprag or it would have zero holding power. But its also much easier to hold for a moment on a downshift during acceleration. The pressure sensor would help yes. If its just a slow shift for 2nd only the transbrake valve body will probably fix that. If the pressure is low then you may need to fix or replace the filter or pump. I've had a 4L80E filter go bad and lose pressure before but when pressure loss happens its usually every gear not just 2nd.

I need to go datalog a second gear pull, but that's really difficult in the middle of a big city. I wish I was still in Michigan with miles and miles of empty roads everywhere.
I did check my trans fluid on the first day, but never again after that.

Yes that would help too, even at 50% throttle to see if it holds on an upshift or even if it holds when it's already in 2nd gear.

 

[r3dd0g]

Thanks for dumping your knowledge on me

 

[Babaganoosh]

Thanks for dumping your knowledge on me

And all of us, Heath helped me with my tuning and corrected my trans from shifting. Although mine is much easier it was still very helpful to learn.

 

[r3dd0g]

If its just a slow shift for 2nd only the transbrake valve body will probably fix that.

The Rossler kit does not replace the valve body. http://www.rosslertrans.com/online-store.html#!/4L80E-Trans-Brake-Kit/p/80029817

If the pressure is low then you may need to fix or replace the filter or pump. I've had a 4L80E filter go bad and lose pressure before but when pressure loss happens its usually every gear not just 2nd.

It took 1 full second from when it commanded 2nd the first time to get into 2nd and .8 seconds from the first time it commanded 3rd to get into 3rd. It was happening in every gear, but once the acceleration was reduced it only took .9 seconds for the 3-2 shift and .4 seconds for the 2-3 shift. I'm thinking it's a pan/baffle issue.

 

[folkenheath]

You are wondering how it works, here is a chart to explain from a sheet that came with some parts I purchased a while back. I realize hard to visualize if you haven't seen/assembled the parts. I can see all these parts in my head having rebuilt some 4L80E trans.

So when in D, if the computer commands 2nd, Sol A shuts off, which applies the intermediate clutch, which causes the intermediate sprag to hold and the low roller clutch (actually more like a sprag) to overrun. A sprag works like a one way bearing, it grabs one direction and free spins the other. Every gear shift just over runs a one way bearing so if the new shift doesn't happen, it's still in the same gear.

So either the circuit that feeds the intermediate clutch is too restricted, or the pressure is too low. The factory restricts the feed with orifices, checkballs, and accumulators (spring loaded pistons that take time to fill up to pressure). All those can be modified, and the checkball and acumulator can even be removed, as long as the orifice isn't too big, that can cause extremely harsh parts breaking shifts. This is parts of mechanical transmission tuning. Too large of orifice can cause the trans to shift too hard, and you can't turn the pressure down or then you lose holding power, as the pressure keeps the clutch applied, less pressure means slower shift, but also less holding power. There is a balance.

The Rossler kit does not replace the valve body. http://www.rosslertrans.com/online-store.html#!/4L80E-Trans-Brake-Kit/p/80029817

It does replace the orifice plate, boost valve, and several springs. I haven't personaly used that exact brake but Rossler has a good reputation. It appears that goes under the PSM and requires a deep pan.

FYI, those springs in the bottom center of the picture are the springs I was referring too that probably go in the direct drum, and it says it requires trans disassembly. So hopefully they already did what I mentioned for those and the bleed hole.

It took 1 full second from when it commanded 2nd the first time to get into 2nd and .8 seconds from the first time it commanded 3rd to get into 3rd. It was happening in every gear, but once the acceleration was reduced it only took .9 seconds for the 3-2 shift and .4 seconds for the 2-3 shift. I'm thinking it's a pan/baffle issue.

If it was a pan baffle issue it would probably be all the gears, not just 2nd. Second might be too restricted.