Twin engine GTP project progress thread

**TwinV6GTP** · 08-26-2014

To me the way it popped out of gear suddenly, felt like it just could hold all the torque off the line. I'm making ridiculous torque on the rear engine now.
Because of the small turbo that spool quickly once it reaches a certain PSI. It takes 3 seconds to build 10 psi but 1 more second it's 20psi, then when I launch it shoots to 28-30 psi almost instantly.
That's when it popped into neutral. Then slammed back in gear after 2 seconds of free revving.

Before this, the trans didn't slip at all, shifted well etc... There was no sign of impending failure. I know for a fact I'm pushing way more torque than that trans was made to handle.

In my opinion the hard parts can take more, but the clutch packs can't.

**91parkave** · 08-26-2014

I'm using all half inch lines for my trans cooler and remote trans filter think that might help in this case?

**darkhorizon** · 08-26-2014

Any boost passed 18ish psi isnt going to flow much more if any air at any rpm on your setup so dont expect to relate psi directly to torquE

**TwinV6GTP** · 08-26-2014

Originally Posted by darkhorizon

Any boost passed 18ish psi isnt going to flow much more if any air at any rpm on your setup so dont expect to relate psi directly to torquE

Yes it does, especially at low RPM when you run a super tight torque converter.
At 22 psi I make great power. From 22 psi to 30 psi, only small gains, mostly torque gains at low to mid RPM. High rpm = no gains.
I get better ET but only slightly better MPH.

25 psi is about the best boost for my set up on my turbos. Over that minimal gains are seen.

Torque is definately very high my guess in the 500 ft-lbs+ at 30 psi

**Turbocharged400sbc** · 08-26-2014

I'm just saying that your not exceeding peak torque capacity if you had a trans with a filter needing replacement.

**TwinV6GTP** · 08-26-2014

Originally Posted by Turbocharged400sbc

I'm just saying that your not exceeding peak torque capacity if you had a trans with a filter needing replacement.

We have the trans apart. Filter blockage was not an issue. It is not perfectly clean but it was not nearly blocked either. Not enough crap there to block it.

The typical 4t80e fixes by Sonnax. One of them check out ok (test explained by sonnax) Shaft leakage = no

We have at least one broken band (low/reverse) clutch packs coming out. garanteed they are damaged.

**SlowFiero** · 08-26-2014

I would take a really good look at the sprag assemblies. What you are describing sounds very similar to what my 65 did when I broke the input sprag. Sometimes it would grab and you could drive slowly, but once you put a load on it, it would fail again, and basically be in nuetral. The last one popped a few times, I could brake boost it a bit, but on launch it would release and the car would not move. Eventually it failed completely and I had no first gear.

**TwinV6GTP** · 08-26-2014

Same symptoms except i get my gear back by messing around driving shiftubg manually. I have most of the trans apart now. Broken low/reverse band and burnt forward clutches.

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**TwinV6GTP** · 08-26-2014

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**PurpleGuy** · 08-26-2014

Sweet

**TwinV6GTP** · 08-26-2014

Even the 4t80e cant take the load. The one i have now has less miles and pan was mint. Nice used fluid as well.

I will keep torque reasonable and run more boost once underway

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**BillBoost37** · 08-27-2014

How sure are you that all that was only you and not previous owner. It was a JY unit without history for the most part.

**TwinV6GTP** · 08-27-2014

Originally Posted by BillBoost37

How sure are you that all that was only you and not previous owner. It was a JY unit without history for the most part.

It ran awesome, over 40 runs testing on the street where traction is a big problem and therefore less stress goes on the transmission clutch packs.
Then 4 runs at the track with high 1.4s 1.5 and 1.6 60 foot.

It shifted well all gear, never slipped or flared. Ran perfect to be honest. Then when I ran way too much boost off the line it released suddenly as if I had snapped the input shaft or the chain.
But it basically slammed back in gear. It's as if I had put it in neutral under power then put it back in gear like a neutral drop.

I wonder if I keep the shifter in the D3 or even D2 position if I reduce the risk of this happening ?

The other theory is like James said and Dark Horizon said. Not enough pressure. I don't think we had a blockage but I can't rule out some pressure loss in the valve bodies.
Also maybe the factory pressure isn't nearly enough for over 500ft-lbs of torque. The 4l80e guys who run 800HP have to run 200 psi of line pressure to hold the power. Not enough line pressure the clutch packs can't hold the power.

**Turbocharged400sbc** · 08-27-2014

no way to be 100% sure. but there arent a whole lot of clutch slippage complaints.

the problem could likely have come from the vb wear issues. we shall see how this one does.

are you gonna shim the accumulators? getting the sonnax fixes or see if the low mile vb holds up?

**darkhorizon** · 08-27-2014

Might want to see what sort of mods you can do to get more line pressure. Doubling it is what makes the 65es work.

**jdredd** · 08-27-2014

Originally Posted by darkhorizon

Might want to see what sort of mods you can do to get more line pressure. Doubling it is what makes the 65es work.

^--- My problem was the line pressure was suppose to be double.. and wasn't... and Matt Runs his at 3x the line pressure.

**TwinV6GTP** · 08-27-2014

Originally Posted by jdredd

^--- My problem was the line pressure was suppose to be double.. and wasn't... and Matt Runs his at 3x the line pressure.

I guess that's done with stiffer springs ?

**jdredd** · 08-27-2014

Originally Posted by TwinV6GTP

I guess that's done with stiffer springs ?

Honestly, I am not 100% sure.. it seems getting these to 300psi isn't super hard... but no idea where he gets the 100+ psi from.

He has no trans cooler. Or at least conventional one that I know of. The stock in/out lines on the bottom of trans just loops to itself. Not sure
if that assists in removing many feet of line. Either hogged stuff out, stiffer springs, and other unknown valve body tricks, or external electrical pump to boost it?

With my trans build at TEP dave said it should easily be 300psi or so... and that with the new converter setup, there is no need for 400+ ... so hopefully that works out.
With some of the stuff dave is doing, and some "secret" things he's got going on, the trans build should take 8's without a problem.. Just need a motor behind it to push
it that far. Getting well into the 9s is my only goal currently.

**Turbocharged400sbc** · 08-27-2014

yeah we should be around 300 or so as well I know we're set up for full line pressure at TCC apply.

by the way this is the oversized boost valve from Sonnax. I've got a few bags of springs over the years from transmissions I'm sure I'd be able to find something in there or at McMaster that would bump up pressure over the OEM
http://www.sonnax.com/parts/2337
Tools.
http://www.sonnax.com/parts/2877

**TwinV6GTP** · 08-27-2014

Originally Posted by Turbocharged400sbc

yeah we should be around 300 or so as well I know we're set up for full line pressure at TCC apply.

by the way this is the oversized boost valve from Sonnax. I've got a few bags of springs over the years from transmissions I'm sure I'd be able to find something in there or at McMaster that would bump up pressure over the OEM
http://www.sonnax.com/parts/2337
Tools.
http://www.sonnax.com/parts/2877

Would you lock TCC under full throttle once off the line ?