Mike...6 speed suncoast valve

[coker6303]

Does this valve from Suncoast maintain line pressure to help 5th and 6th gear shifts and would it be a good addition on top of the Transgo Jr?

Thanks!

Russ

2004.5-07
Part No. A1-LU-BST-04
Price: $86.00

This valve controls fluid flow to the converter clutch and reduces main line pressure from 255 PSI to 155 PSI when the converter clutch applies, In the LB7 transmission the TRANSGO® A1-LU-BST valve allow the amount of cut-back to be controlled so that main line stays at up to 190 PSI. The LB7 valve will not work on late LLY units. The LLY units require the Sun Coast A1-LU-BST-04 valve for pressure control.

 

[JoshH]

That is the converter flow valve or cut-back valve. It keeps the pressure up when the converter clutch locks. Really doesn't have anything to do with 5th or 6th gear.

 

[othrgrl]

That valve reduces the cutback when the converter clutch applies. As you can see in the description the stock valve cuts 100 PSI from main line pressure when the converter is locked. The A1-LU-BST and A1-LU-BST-04 will only cut about 40 PSI from main line pressure. It's not for the shifts but actually just to hold the clutches tighter and will help reduce the chance of slipping the clutches while the converter is locked. The valve is not located in the valve-body though and you would have to remove the transmission, remove the bell housing, remove the pump from the bell housing, and split the pump in half to get to it.

 

[JoshH]

You don't have to split the pump in half to get it out.

 

[coker6303]

thank you! If I am dropping the tranny then this little valve will be at the bottom of the mod list. I was thinking it was in the valve body. Nice to know!

 

[othrgrl]

You don't have to split the pump in half to get it out.

You can see it (the end of it) without even removing the pump from the bell housing - but to remove it you have to remove the pump from the bell housing, remove the 5 10mm bolts and take the back side of the pump (the stator) away from the plate.

 

[JoshH]

Ok, I'm with you now. I thought you were saying you need to get to the inside of the pump to get to the valve.

 

[Mike L.]

That is the converter flow valve or cut-back valve. It keeps the pressure up when the converter clutch locks. Really doesn't have anything to do with 5th or 6th gear.

It actualy does. Normal 6 speed operation locks the converter right on top of the 4/5 shift and pressure drops. When the pressure drops from 245 psi to 145 psi; it drops all across the board so the clutches only get 145 psi. Tow/Haul is the same thing. Anytime the converter locks the pressure drops across the board.
If you are running big horsepower like MPI twins; you need to modify the Transgo valve for no knock down as the Transgo valve still has some knock down if installed as is.

 

[JoshH]

All I was saying, Mike, is the pressure drops with the converter clutch, not 5th or 6th gear. Like you pointed out, T/H mode has a different scenario in which the converter locks in 2nd gear which is when the pressure would drop. Right?

 

[Mike L.]

All I was saying, Mike, is the pressure drops with the converter clutch, not 5th or 6th gear. Like you pointed out, T/H mode has a different scenario in which the converter locks in 2nd gear which is when the pressure would drop. Right?

Did you miss my point Josh? TCC occurs on top of 5th gear in a 6 speed in O/D. That means as soon as it hits 5th TCC occured and pressure dropped. Holding power in 5 lost 100 psi and the shift into 6th was at 145 psi at best. That is why we are seeing C4 clutch getting wasted in the 6 speed when it never got hurt in the 5 speed. C4 clutch is now getting the same heat cycles as C3 because it is once again applied for 6 th gear.

 

[JoshH]

Did you miss my point Josh? TCC occurs on top of 5th gear in a 6 speed in O/D. That means as soon as it hits 5th TCC occured and pressure dropped. Holding power in 5 lost 100 psi and the shift into 6th was at 145 psi at best. That is why we are seeing C4 clutch getting wasted in the 6 speed when it never got hurt in the 5 speed. C4 clutch is now getting the same heat cycles as C3 because it is once again applied for 6 th gear.

I see what you're saying, and thank you for explaining it further. What modification is needed for the transgo valve that you mentioned earlier?

 

[rcr1978]

i see what you're saying, and thank you for explaining it further. What modification is needed for the transgo valve that you mentioned earlier?

x2 ? :d

 

[Flyinfrenchman]

I'll start by saying hi... been a long time lurker just don't post very often.

But how about installing it without the spring? Would one have to restrict flow downstream?

 

[Mike L.]

I'll start by saying hi... been a long time lurker just don't post very often.

But how about installing it without the spring? Would one have to restrict flow downstream?

Without the spring installed the valve would move back and forth at will and cause all kinds of problems.

 

[coker6303]

Mike, I'm still curious on the pressure drop. Like Josh asked, would Tow Haul cause the 100psi pressure drop to occur in second gear when the TCC locks up or does the pressure drop only occur at 5th gear lockup regardless of 2-4 TCC lockup? This would mean that Tow Haul would be bad for those racing with stock trannies since they are working with very limited pressures from 2nd gear up.

 

[Mike L.]

Mike, I'm still curious on the pressure drop. Like Josh asked, would Tow Haul cause the 100psi pressure drop to occur in second gear when the TCC locks up or does the pressure drop only occur at 5th gear lockup regardless of 2-4 TCC lockup? This would mean that Tow Haul would be bad for those racing with stock trannies since they are working with very limited pressures from 2nd gear up.

Anytime the converter flow valve strokes to apply TCC, pressure will drop. Doesn't matter if you're in T/H or O/D.

 

[coker6303]

Thank you!

 

[JoshH]

Just to clarify, whether you are in T/H or not, at WOT, lockup occurs in 2nd gear (or is supposed to). Is that correct, Mike?

 

[Dozerboy]

Yes

What modification is needed for the transgo valve that you mentioned earlier?

Anyone?

 

[Mike L.]

Just to clarify, whether you are in T/H or not, at WOT, lockup occurs in 2nd gear (or is supposed to). Is that correct, Mike?

Correct.
In O/D TCC occurs at the top of 2nd gear and in T/H it occurs midway through 2nd.