3800 4T80E>4t60/65/hd
- Thread starter Turbocharged400sbc
- Start date
But seriously, it needs some serious attention. I understand it not lasting...
but burning up so quickly is unreal...
Definately no TH400 ...
I will have to upgrade every circuit and make it shift clean and crisp.
Maybe then it can hold 800HP we'll see...
Pretty discouraging though. If it lasted a little while stock it would be promising but it doesn't...
I'm thinking of possibly making it a race only trans and disable some stuff. Losing the park/reverse/neutral and 4th gear.
Who knows how to proceed about deleting the forward sprag ?
We figured out another way without welding... cnc drilling holes through the gears and insert press pins all around that is welded at the end. That will lock both gears together cancelling the sprag. The plastic spacera would be replaced by machined steel replacements spacera also drilled and with pins
Doing more research on this, it seems the UPGRADE for the TH400 comes from the 4t80e... they call it the 36 element Super Sprag and it holds more than 1000HP up to 1500HP...
So our sprag is made very strong, yet something causes it to fail at much lower HP. Weight of rotating assembly ? Failure of the coast clutch ?
Debris from the nearby coast clutch contaminating and jamming the sprag ?
We are slowing getting somewhere...
I just bench tested the coast clutch and the Forward clutch packs on the bench using the forward drum support. And strange findings...
There are two holes on the side of the drum, which I believe can be used for testing.
I do not have the service manual so I have to improvise. Let me know if those are not appropriate...
The right hole puts more pressure on the forward clutch packs. Although there is crossleak into the left port and partial pressurization of the coast clutch (they never lock). putting the finger on the left port to block air coming out raises both clutch packs (the coast clutch not much pressure, forward clutch lots of pressure)
Pressurizing the left port puts a little pressure on the coast clutch. Not enough to lock them. tried putting heavier grade oil in the port, still not much sealing. Air bubbles coming out of the circlip area...
Putting finger on the right port to block cross leak of air, then the coast clutch apply well and forward clutch also partially apply (not strong)
Both supports and both drums performed very similar.
Is this normal ??
It just looks like a big leak problem to me and a good explanation why the coast clutch fail. Poor apply, lots of cross leakage etc...
So our sprag is made very strong, yet something causes it to fail at much lower HP. Weight of rotating assembly ? Failure of the coast clutch ?
Debris from the nearby coast clutch contaminating and jamming the sprag ?
We are slowing getting somewhere...
I just bench tested the coast clutch and the Forward clutch packs on the bench using the forward drum support. And strange findings...
There are two holes on the side of the drum, which I believe can be used for testing.
I do not have the service manual so I have to improvise. Let me know if those are not appropriate...
The right hole puts more pressure on the forward clutch packs. Although there is crossleak into the left port and partial pressurization of the coast clutch (they never lock). putting the finger on the left port to block air coming out raises both clutch packs (the coast clutch not much pressure, forward clutch lots of pressure)
Pressurizing the left port puts a little pressure on the coast clutch. Not enough to lock them. tried putting heavier grade oil in the port, still not much sealing. Air bubbles coming out of the circlip area...
Putting finger on the right port to block cross leak of air, then the coast clutch apply well and forward clutch also partially apply (not strong)
Both supports and both drums performed very similar.
Is this normal ??
It just looks like a big leak problem to me and a good explanation why the coast clutch fail. Poor apply, lots of cross leakage etc...
I have a few possibilities here.
Given what I found so far, I think there is some potential for it holding some 700-800HP with the right valve body mods:
-Firmed up accumulators -> or simply cancel the accumulators
-Reduce spring tension on shift valves for quicker shifts
-Increased orifice feed size to quicken the shift and more positive clutch engagement. This might really help a lot on a transmission starting to lose sealing ability.
-increase line pressure (any tips here would be appreciated). There are a few ways this can be done but there might be concerns with too much pressure and some circuits to relieve etc...)
Other mods:
-Brand new clutch packs and new plates, new seals everywhere, new shafts/bores for maximum hydraulic pressure and minimal leaking etc...
-Delete wave plates, try and squeeze an extra friction/steel.
-reduce spring number in clutch baskets to increase pressure on the clutch packs for any given hydraulic pressure setting (this might have a downside of slowing down release, not sure if that is the best thing to do)
------------
Driver technique:
Always stay in D3 (manual range) no matter what.
-Coast clutch is always fully applied. Might help save that clutch pack.
May go back to 2nd gear starts to avoid stress on drivetrain during 1-2 shift.
---------------------------------------
Experimental mods:
Deleting the sprag (welding or locking it mechanically)
This will force the transmission into a Forward motion. It won't be able to park/reverse or go neutral. At the same time, I would leave it in D3 all the time. The Coast clutch would be fully applied and Forward clutch as well. Basically the whole drum would work as a unit, improving the strength and having amazing engine braking...
This should in theory eliminate the two biggest weakness.
But I would lose reverse, neutral and park. Would start in gear so a tight converter will make for a harder car to start.
Going even crazier with this idea, find a way to lock the clutches inside the drum 100% Preventing any possible slippage at any power level.
3rd clutch would then be the next weakness (it has some hot spots and wear)
2nd clutch looks really good in all transmission, so far doesn't seem to be a concern.
Given what I found so far, I think there is some potential for it holding some 700-800HP with the right valve body mods:
-Firmed up accumulators -> or simply cancel the accumulators
-Reduce spring tension on shift valves for quicker shifts
-Increased orifice feed size to quicken the shift and more positive clutch engagement. This might really help a lot on a transmission starting to lose sealing ability.
-increase line pressure (any tips here would be appreciated). There are a few ways this can be done but there might be concerns with too much pressure and some circuits to relieve etc...)
Other mods:
-Brand new clutch packs and new plates, new seals everywhere, new shafts/bores for maximum hydraulic pressure and minimal leaking etc...
-Delete wave plates, try and squeeze an extra friction/steel.
-reduce spring number in clutch baskets to increase pressure on the clutch packs for any given hydraulic pressure setting (this might have a downside of slowing down release, not sure if that is the best thing to do)
------------
Driver technique:
Always stay in D3 (manual range) no matter what.
-Coast clutch is always fully applied. Might help save that clutch pack.
May go back to 2nd gear starts to avoid stress on drivetrain during 1-2 shift.
---------------------------------------
Experimental mods:
Deleting the sprag (welding or locking it mechanically)
This will force the transmission into a Forward motion. It won't be able to park/reverse or go neutral. At the same time, I would leave it in D3 all the time. The Coast clutch would be fully applied and Forward clutch as well. Basically the whole drum would work as a unit, improving the strength and having amazing engine braking...
This should in theory eliminate the two biggest weakness.
But I would lose reverse, neutral and park. Would start in gear so a tight converter will make for a harder car to start.
Going even crazier with this idea, find a way to lock the clutches inside the drum 100% Preventing any possible slippage at any power level.
3rd clutch would then be the next weakness (it has some hot spots and wear)
2nd clutch looks really good in all transmission, so far doesn't seem to be a concern.
Looked at the 4t80e i had last year it was slipping in 3rd gear and 4th... at 600hp but even more torque.
3rd lots of hot spots...
All other clutches like brand new...
Sprag good.
So that point towards a hydraulic issue with the forward and coast drum. The seals can de damaged easily because they always spin against the 1-2 roller especially at high speed. Any lubrication issue or clutch pack grit could quickly reduce their sealing ability.
Because if it was a matter of them being too weak, they would all be destroyed. This last 4t80e from last year took a lot of abuse but at power levels not as high as this year. shows that the Forward clutches are NOT supposed to slip (they are beefed and numerous)
And that the Coast clutch isn't suppose to burn itself out. It looked brand new in there as it should (it's not supposed to be used)
That points towards seal leaking/cross talk. Forward clutch pressure going into the coast drum partially applying it and burning it out during decel...
a fresh 4t80e with new unshrunk seals would probably fair much better especially combined with a race valve body calibration.
Found a way to fix the forward and coast clutch situation now its 3rd gear we have to watch. Lots of pressure and quick shift will help...
We also found most of the trans or all of it can be rebuilt in car...
2 to 3 hour job with a fresh cartrige ready to slide in.
3rd lots of hot spots...
All other clutches like brand new...
Sprag good.
So that point towards a hydraulic issue with the forward and coast drum. The seals can de damaged easily because they always spin against the 1-2 roller especially at high speed. Any lubrication issue or clutch pack grit could quickly reduce their sealing ability.
Because if it was a matter of them being too weak, they would all be destroyed. This last 4t80e from last year took a lot of abuse but at power levels not as high as this year. shows that the Forward clutches are NOT supposed to slip (they are beefed and numerous)
And that the Coast clutch isn't suppose to burn itself out. It looked brand new in there as it should (it's not supposed to be used)
That points towards seal leaking/cross talk. Forward clutch pressure going into the coast drum partially applying it and burning it out during decel...
a fresh 4t80e with new unshrunk seals would probably fair much better especially combined with a race valve body calibration.
Found a way to fix the forward and coast clutch situation now its 3rd gear we have to watch. Lots of pressure and quick shift will help...
We also found most of the trans or all of it can be rebuilt in car...
2 to 3 hour job with a fresh cartrige ready to slide in.
It will be hard to reach his level, but my goal is find a solution for the 4t80 at least.
If you look at the aftermarket in the TH400 or 4l80e, the potential is up to 3000HP now.
we will never reach that kind of potential with a FWD transmission.
But a stock Th400 is only good for around 500HP bone stock. Any more and the trans is on borrowed time... Simple mods make it handle almost double that.
Many of the problems of the TH400 are similar to the 4t80e.
So we can apply some of the stuff that improves other transmissions (4t65e-HD, TH400, 4l80e) etc...
But also learn the key differences and what can be done specifically to the 4t80e to improve it's own set of weaknesses.
I have high hopes that 700-800HP is possible without deleting the sprag with some work. And more than 800HP we may have to delete the sprag and other weaknesses.
Unless I have custom clutches made to increase the number of frictions and also use a higher coefficient of friction material in them, the 3rd gear will be the hardest to correct. So I have to make phone calls and see who can build them for me and at what cost.
im glad your seeing the 80e's possibilities.
iit does show that new bushings are a requirement, remember the drivers side axle leaking issue is related to the 3rd clutch bushing being worn and allowing pressurized oil to fill that area of the driven sprocket support.
that area of the coast clutches crosstalking doesn't seem to be preventable with stronger piston return springs as the same springs act on the two concentric pistons. also keep in mind the apply plate flex is an issue on the L80. when you look at the production years it would seem that the L and T were designed in the same timeframe and using more than a few of the same parts/dimensions, likely it was offered later due to the extra complexity (and that whole early die casting warpage issue (there was a tsb about the early t80e's having pressure leaks due to case settling as the die casting mold cooling was a problem with cast in stress causing issues after "seasoning" aka use
the sprag I think has the problems off the line is the lo roller sprag so maybe something akin to a 2nd and 3rd only trans with the old 2.84 diff would be the hot ticket lol
I honestly feel that the first hard part to break will be the IS, probably at the tcc oring...
bumping pressure via the main spring, even without a new spool valve shoulder to ramp in the 2nd pump earlier, up afl pressure should probably be thought about fer sure....I mean the shift valves etc will likely be worn
bumping converter pressure can be done. I know PI and dave both say youll drag the tcc clutch loading up on the line just from the extra dynamic pressure on the plate during multiplication.
drilling the passages in the separator plate would be terrific. possibly leaving out the check balls in the "bypass's"
with the pumped side of the accumulators probiding a signal to the shit valves for up/down shifting id wonder what the effect of solid or nearly solid accumulators might mean since some paths past the valves are not counter-balanced...moving the valve
there might be some caveats here....
plus the scanner sucks ass and its not picking up the pages near the binding. im loath to cut apart this damn thing so I may be stuck taking pics of every god damn page to do it
So its confirmed... swapping internals of the 4t80e in our race car is just a 2 hour job. no need to remove the transmission.
Great news.
You pull the whole cartridge from the diff side. You pull the pan unbolt the bottom valvebody and remove two bolts that hold the support. Then remove the diff and parking pawl. Then pulling the fitting you use a rubber protected flat head to save the thread and pry out the support. The rest comes out easy. I have an assitant pry gently on the reverse housing.
It all comes out but the 2nd gear friction and steels. Putting it back is reverse but you fiddle a little more sliding the 2nd gear sprag into the 2nd clutches. Luckily they are pretty loose in the case and can wiggled from the bottom by an assitant.
Best done with a chain block or an electric hoist like I use. We will build a cart with bottom opening for the purpose.
Great news.
You pull the whole cartridge from the diff side. You pull the pan unbolt the bottom valvebody and remove two bolts that hold the support. Then remove the diff and parking pawl. Then pulling the fitting you use a rubber protected flat head to save the thread and pry out the support. The rest comes out easy. I have an assitant pry gently on the reverse housing.
It all comes out but the 2nd gear friction and steels. Putting it back is reverse but you fiddle a little more sliding the 2nd gear sprag into the 2nd clutches. Luckily they are pretty loose in the case and can wiggled from the bottom by an assitant.
Best done with a chain block or an electric hoist like I use. We will build a cart with bottom opening for the purpose.
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...
So we did some more work. Took out the 4t80e trans from my car to make the adjustment for the trans/motor bracket in order to be able to do the in car transmission work. So we took this last 4t80e apart.
That one went neutral in 3rd then got stuck in 3rd gear. Next day it looked normal. Could burnout in 2nd-3rd gear (without glue). Took the pan off and it was FULL of clutch material.
Surprised to see only 3rd clutch pack is destroyed (the worst of all the 4t80e i have hurt)...
This trans did 1st gear starts and shifted very slow and sluggish, especially 2-3. 2nd gear always has a few leopard spots but nothing bad.
This trans was 100% stock low miles 2008 4t80e.
So there is pretty solid evidence that the Forward clutches, coast clutch and forward sprag take a beating mostly when doing 2nd gear take off on glue at very high boost. Something the 4t65e-HD doesn't have a problem with surprisingly (size for size of course).
This trans had PERFECT forward clutches and perfect coast clutch.
What I will try first is taking out the reverse clutch pack and piston to save weight in that critical reverse drum. The one that stops and has to spin again going into 3rd gear. Also will do a in depth shift kit.
I'm still digging at the diagrams that I have which are incomplete.
James if you read this, please scan the 4t80e power flow and hydraulic flow chart in color (the ones where you see hydraulic fluid path in each gear). That would save me some time. I'd love to complete this tomorrow.
I want to drill out forward clutch feed,coast clutch feed, 3rd clutch feed and 2nd clutch feed as well as improve grip on the 4th band to assist in engine braking and possibly helping the sprag not take all the load even getting in and out of throttle during 2nd gear burnouts.
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