3800 4T80E>4t60/65/hd

formula

New member
Aug 12, 2015
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honestly street tire, I don't think you go through a 4t80e. especially a fresh one with some of EP's mods inside (quicker shifts and more pressure).
Even with small slicks you probably couldn't hurt it. Right now I have the 3.11 gears and 29.5" slicks and ridiculous amount of torque and that really loads the transmission hard.

I wouldn't even worry...

Cool, I run a 235 mt et street on it. Last year it made 550whp on 93 and used a zzp stage 3 (7/8th chain) 4t65 and a pte6262. This/Next year I'm adding the zzp aluminum heads, pte6466, e85 and arp head studs with the 4t80. I'm thinking I can get it up to 650-700whp. I don't generally launch it very hard, but I do hot lap it a lot in the 1/8th mile at a local unprepped event.

Do you have any insight into how the twin engines affect the trans?
 

twinv6gtp

Turbo enthusiast
Jul 27, 2014
837
4
Used or new the alu heads ?

The best parts about the head you will need a lot less octane for the same power.


The twin engine launches very hard compared to a fwd. That means the rear tire see a lot of weight and therefore traction.

Fwd cars cant hook 700 to 800 whp off the line normally. Unless its a pro setup on a perfect glued track and even then...

So your fwd 4t80 will not see the same load as mine.
 

formula

New member
Aug 12, 2015
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heads were new - got the black friday discount, plus another couple hundred off from other things

car is rwd (fiero is fwd setup in the rear), but I don't launch it nearly as hard as you do (on the 4t65e I launched on the converter at 3psi for a 1.6 60')

I never thought of the front engine pushing back on the launch too, that probably is really hard on the rear trans.
 

Turbocharged400sbc

3800 & 4T80E > ALL
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Jun 16, 2007
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well ive got a good strong design for the engine to diff brace. it fairly easy to get at the block side bolts with the F body/W oil neck but the G/H guys are sorta stuck jamming their hands between the engine and diff from the side as opposed to to access from the bottom... but I may rework it to a two piece affair


sure beats the piece of angle iron I had been using...
 

twinv6gtp

Turbo enthusiast
Jul 27, 2014
837
4
well ive got a good strong design for the engine to diff brace. it fairly easy to get at the block side bolts with the F body/W oil neck but the G/H guys are sorta stuck jamming their hands between the engine and diff from the side as opposed to to access from the bottom... but I may rework it to a two piece affair


sure beats the piece of angle iron I had been using...

We just reworked the bracket. Now it's a 2 piece design and can be removed while the trans is on the block. allowing an easy access to rebuilding the 4t80e while in the car... Saving a few hours of unplugging and removing stuff.

I also designed a sub tank on the side cover. This will add at least 2 liters of additional fluid in the best location right where the main filter is. Also in fabrication at the CNC shop, a one piece billet aluminum deep pan with a lot more fluid capacity a much thicker/stronger design to prevent flexing of the case (a weak area, since the lower valve body actually doubles as brace lol..)

I think a lot of the issues of the 4t80e are due to flexing and losing hydraulic pressure at critical time (big torque, high traction)
Which may be why I went neutral suddenly under high load during launch in 2nd gear.

So I'm addressing 2 issues at once, more fluid available in case it get low during a long stall and hard launch causing air to get sucked in...

And more fluid in the bottom pan helping reduce frothing of the fluid during scavenging of the lower pan. This will help reduce the chance of air bubbles in the scavenged fluid being pumped into the side cover.

The pan will also be super strong helping boxing in the case of the transmission.
 

Turbocharged400sbc

3800 & 4T80E > ALL
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Jun 16, 2007
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We just reworked the bracket. Now it's a 2 piece design and can be removed while the trans is on the block. allowing an easy access to rebuilding the 4t80e while in the car... Saving a few hours of unplugging and removing stuff.


yeah i was looking at making the block side hit all three 12mm skirt bolt holes...the one near the knock sensor is sorta a pita so a 1 piece wouldnt work for easy trans service, but the 3 would give the final drive/differential ring gear alot more support.


I also designed a sub tank on the side cover. This will add at least 2 liters of additional fluid in the best location right where the main filter is. Also in fabrication at the CNC shop, a one piece billet aluminum deep pan with a lot more fluid capacity a much thicker/stronger design to prevent flexing of the case (a weak area, since the lower valve body actually doubles as brace lol..)

I think a lot of the issues of the 4t80e are due to flexing and losing hydraulic pressure at critical time (big torque, high traction)
Which may be why I went neutral suddenly under high load during launch in 2nd gear.
i like the side cover volume increase....that never hurts dry sump systems...but the scavenge pump discharges are upward and downward. i was planning on tossing some teflon swarf/cuttings in there to give it a baffle that wont hurt any electronics but will make sure that the air can float out of suspension.

id hate to say it but most of that is due to using the oem mounting points that arent anywhere near the case bulkheads where all the tq reactions take place... look at how little meat is through that area of an empty case...and you cant count on the center suport as it only bolts to the case via the lube/cooler circuit....so its not doing anything.

our mounts go straight to the channel plate/case bulkhead and the differential/ring gear bulkhead, all loads are in shear through those bulkheads...distortion should be near zero since there are no longer any bending loads with tons of leverage like the oem mount

So I'm addressing 2 issues at once, more fluid available in case it get low during a long stall and hard launch causing air to get sucked in...

And more fluid in the bottom pan helping reduce frothing of the fluid during scavenging of the lower pan. This will help reduce the chance of air bubbles in the scavenged fluid being pumped into the side cover.

The pan will also be super strong helping boxing in the case of the transmission.

always a good idea, an external cylindrical dry sump tank would be great lol, maybe if the trans side cover keeps us from stuffing 16" shoe's out back it may be our best option. we are looking at putting the trans/engine puke tanks over the drivers side axle housing so with the trans vent taken care of i was planning on just running the side cover over full.

on the bottom pan thats not gonna do much of anything, by its nature and those filters your always going to be sucking in air bubbles... baffling in the side cover is the best fix....the scavenge pump that discharges downward may be the one making all the trouble...one reason i was planning on the teflon swarf/wool.

cant hurt to make it more rigid, but without moving away from the oem mount your not gonna see a whole lota change...(a packaging compromise undoubtedly....as it uses the same mounting brackets as the 65e G&H bodies.)
 

twinv6gtp

Turbo enthusiast
Jul 27, 2014
837
4
yeah i was looking at making the block side hit all three 12mm skirt bolt holes...the one near the knock sensor is sorta a pita so a 1 piece wouldnt work for easy trans service, but the 3 would give the final drive/differential ring gear alot more support.



i like the side cover volume increase....that never hurts dry sump systems...but the scavenge pump discharges are upward and downward. i was planning on tossing some teflon swarf/cuttings in there to give it a baffle that wont hurt any electronics but will make sure that the air can float out of suspension.

id hate to say it but most of that is due to using the oem mounting points that arent anywhere near the case bulkheads where all the tq reactions take place... look at how little meat is through that area of an empty case...and you cant count on the center suport as it only bolts to the case via the lube/cooler circuit....so its not doing anything.

our mounts go straight to the channel plate/case bulkhead and the differential/ring gear bulkhead, all loads are in shear through those bulkheads...distortion should be near zero since there are no longer any bending loads with tons of leverage like the oem mount



always a good idea, an external cylindrical dry sump tank would be great lol, maybe if the trans side cover keeps us from stuffing 16" shoe's out back it may be our best option. we are looking at putting the trans/engine puke tanks over the drivers side axle housing so with the trans vent taken care of i was planning on just running the side cover over full.

on the bottom pan thats not gonna do much of anything, by its nature and those filters your always going to be sucking in air bubbles... baffling in the side cover is the best fix....the scavenge pump that discharges downward may be the one making all the trouble...one reason i was planning on the teflon swarf/wool.

cant hurt to make it more rigid, but without moving away from the oem mount your not gonna see a whole lota change...(a packaging compromise undoubtedly....as it uses the same mounting brackets as the 65e G&H bodies.)

It just seems like the bottom of the case has very little material. Under high load I bet this case flexes. The valve body bolted under the thin case acts as a reinforcement. Not helping with potential hydraulic leaks under high load.

I suspect more and more that During high boost launch I completely lost hydraulic pressure. Either from emptying the side tank or lowering volume enough to cause some air to reach the pickup. Or it might be because the case flexed and I lost hydraulics either on the left side axle area, which is also very thin and under load when the 2nd gear is engaged. The bottom could also be in cause.

The fact there was a TSB for warped channel plates is another indicator of a potential issue. And that's on STOCK Northstars... not an 800HP engine.
 

Turbocharged400sbc

3800 & 4T80E > ALL
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Jun 16, 2007
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the planetary section is tq loading around the axle centerline. all tq loads are essentially a shear load through the aluminum "tube" of the planetary section. dep on gear the tq loads can be working against each other within 4-5" of the case (a ring forced counterclockwise while the planet next to it is forcing its ring clockwise)

the problem comes when you mount that tube to a stationary object....and then exert bending loads into the middle of it at high hp/tq....you get deformation of the tube and then the internals are no longer spinning concentric.

even by making the lower portion of that oem mount stiffer...you cant make the upper stiffer, and its still going to try and crush the tube.

mount the tube at both ends in shear...and you just eliminated a massive amount of flex.

the left side axle area has the case bulkhead, channel plate, and cover, if anything id say that's the strongest area next to the final drive planets section.

overfilling it and running the breather hose to a puke tank is one way to test and possibly solve the issue. old even slightly clogged wet sump filters would contribute to the issue.

there are tsb's for warped channel plates, accumulator plate, etc. same with damn near every other mass produced trans. I remember lapping 350/400/700r4 valvebodies on a surface plate....hell I remember how thin the 400's case is...and they run those up pretty high...with just a bellhousing. because the pimary load is a rotational tq down the tube...only bending loads are at the trans mount and its more a rocking motion...engine mounts take most of the tq

im sure if you bolted a 400 to a vehicle using 3 lugs on the side of the case, in the middle of the clutches/drums/bands. it would not like it in the slightest.

you can reinforce the case via the dry sump pan area, but your oem mounting is an oem compromise thats not helping you, or the trans handle more than oem power.

don't get me wrong, I know it needs more/stable pressure, and likely more volume... but you may be tackling the flex problem from the middle instead of from the ends :s00ls:
 

twinv6gtp

Turbo enthusiast
Jul 27, 2014
837
4
My custom Side cover seems to be a success so far on the 4t80e.

After installing two Turbo Dynamics Custom pressure gauges (0-500psi) with warning light (similar to a shift light) that is programmable for low and high...

Lets start with the front transmission:
4t65e-HD with Dave's special valve body for extra pressure and quick shifts (which really helped btw...) and Dave's special HD racing clutch packs.

I set the low warning to 220 for the front trans (pressure is normally 340-380psi cold) and 250-260psi hot...

During the run you can clearly see the and read gauge on the Go-Pro.
Multiple times during the run you can see the pressure oscillating between 200-260psi and sometimes sticking at 200 psi (and lighting the red warning light) But the most alarming was exactly when I press the shift button and went to 3rd gear. The pressure immediatly dropped to 150 psi. No wonder these 4t65e-HD have weak 3rd gear. It doesn't seem to be starved for oil pressure in my case. Because it recovers after the shift to 3rd. It just seems that opening the hydraulic circuits to feed 3rd gear causes a drop in total line pressure. This has to be investigated. I will still make a special deeper pan but I doubt this is the main problem. Because it recovers and does not drop pressure during initial High G acceleration. Also something odd is a massive difference between cold trans fluid pressure and hot fluid pressure 340 psi vs 240 psi !

I know some of the old school drag racers use ice to cool their trans fluid !
maybe that's why.

4t80e...
Bone stock low miles 2010 trans.
We built a side cover for it that holds an extra 4-5 pints. Total of 15 pints LOL !!

I always suspected issues with pressure drop with the stock cover. Almost every failure where pressure related. Dropping to zero during hard acceleration off the line. But I have no proof.

My goal was to test the trans to the limit last weekend but a stupid ARP bolt backing out issue stopped me from testing to the very limit.

But so far so good, no failure in many many runs (2 weekends of racing)

During 1/4 mile video you can see the Pressure is 200-210 psi in gear and extremely steady. Very little change. Maybe 10 psi raise at high rpm vs low rpm. No drop between gears...

that's quite different than the pressure dropping 4t65e-HD !!!
 

Rent Free

TCG Elite Member
Jan 26, 2015
24,425
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Nowheresville North Dakota
You got those brackets for the diff side? I thought he made you some chassis mounts for the twin engine monster? If I was on my laptop I could link the pics in the bertha thread on GPF

Finally have a damn 2 car heated garage at home so I need to mock a 4t80/3800 in my caged car once I get home. Some prefab shizzzz would be out fucking standing!!
 

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