T-400 Direct Drum Question

[Alky V6]

But you are limited to the high static clutches with the 4t80 race

The super sprag setup that uses the 4T80E clutches is a 5 friction plate setup (a 10 disc pack). And, you're right. I am limited to only the high energy frictions. But, they work good, and I actually prefer them, so that's a good thing. The 4T80E pack is more than enough to be effective. In fact, maybe a little too effective,.. for my particular track, anyway.
It's effective enough that I feel comfortable simply using regular steels in that clutch pack. Practically, zero heat marking of the steel plates in the intermediate. I even added springs to all the return spring pockets of the intermediate piston in attempts to soften up the 1-2 shift, to no avail, by the way.

 

[chris718]

The super sprag setup that uses the 4T80E clutches is a 5 friction plate setup (a 10 disc pack). And, you're right. I am limited to only the high energy frictions. But, they work good, and I actually prefer them, so that's a good thing. The 4T80E pack is more than enough to be effective. In fact, maybe a little too effective,.. for my particular track, anyway.
It's effective enough that I feel comfortable simply using regular steels in that clutch pack. Practically, zero heat marking of the steel plates in the intermediate. I even added springs to all the return spring pockets of the intermediate piston in attempts to soften up the 1-2 shift, to no avail, by the way.

The more springs you add the firmer it will shift.The spring hold the piston back until more pressure is reached in the circuit creating a firmer shift ,backwards of what some might think.

 

[chris718]

I have a 5 friction direct drum with an aluminum piston and a 34 element sprag. Can this drum/piston be machined to accept 6 frictions? Can you give me the dimensions on the machine work?

Dave

Dave you may find this useful .It is from the CK TH400 MANUAL.
If you will be using an early TH400 34 element direct drum or a late TH400 drum that has been outfitted with a 36 element intermediate sprag some things should be noted in regards to the overall work surface height of the piston, and the location of the groove from the manufacturing process .The groove location height is different in these type of production drums. There were dimensionally different types of these drums manufactured over the production life of the TH400.There are also occasional machining errors. We have developed a measuring technique that will help you identify the piston with the correct “minimal” overall work surface height for the clutch drum being used. This technique can also be used for the production 4L80E clutch drums; however we have already provided all of the information necessary in regards to overall work surface height that you will need with production 4L80E parts. Also keep in mind there were 5 and 6 clutch production TH400 direct clutch drums. This is covered in the direct drum section on page.
Using a suitable method measure from the base of the drum where the clutch piston rests to the top of the first step in the drum. This dimension plus the groove width is what we will call the clearance height. The average width of the machined manufacturing groove is .125”. We must now add .030” to the clearance height. This .030”allows is the amount above the clearance groove that the steel plate must be at so it can’t fall into the groove. Now you simply subtract the thickness of the steel you are going to use, either .080” or .093”, and this is the minimum overall work surface height that the piston can be for the drum being used. Remember this is the minimum, not the maximum. It may be necessary for the piston to have a greater overall work surface height for proper clutch pack clearance. Once you have determined the piston you will be installing, place it in the drum and stack up the steel plates, clutch plates and pressure plate and get an idea of what changes need to be made to the piston or to the steels to arrive at the proper clutch pack clearance.

The recommended direct clutch pack end clearance for a 6 friction clutch pack for an automatic shift 4L80E without a transbrake is.035” to .060”. The recommended clutch pack end clearance for a 6 friction clutch pack for an automatic or manual shift 4L80E with a transbrake is .040” to .065”.

If you are going to be using a production 4L80E direct clutch drum, the following combination of parts will get you very close to the recommended clutch pack end clearance. Use an aluminum clutch piston with the minimal overall work surface height @ .610”, 5 .080”steel plates,1 .093” steel plate, and 6 .085 high energy clutch plates. You can use thicker steels to reduce clearance. This will allow you to reduce clearance in .013” increments.

 

[Alky V6]

The more springs you add the firmer it will shift.The spring hold the piston back until more pressure is reached in the circuit creating a firmer shift ,backwards of what some might think.

Wouldn't that also depend on how close the combination is to the static appied slippage threshold?

 

[chris718]

Wouldn't that also depend on how close the combination is to the static appied slippage threshold?

Donnie,I lost you.Please explain differently and maybe I will get it.Not being an ass,I just dont understand.

 

[Alky V6]

Donnie,I lost you.Please explain differently and maybe I will get it.Not being an ass,I just dont understand.

Once the clutch pack has applied there will be a certain torque input value to that clutch pack that will cause it to slip. This is after it has already applied and is simply holding against the torque input. The friction coeficient of the friction plates, friction surface contact area, hydraulic pressure minus any return spring pressure, and apply piston area are the main factors keeping the clutch pack from slipping against the torque input. Lowering the hydraulic pressure may allow the frictions to slip, if the clutch pack is on the edge of doing so. Friction plate surface area and the friction coeficient of the material will determine at what pressure the clutch pack begins to slip.
The pressure of the return springs against the apply piston is a force that is counteracting the hydraulic apply pressure. When the clutch piston has completed its stroke, the overall apply pressure will be less with heavier return springs. The pressure during application of the clutch with heavier return springs will be higher, but the apply orifice, if any, is still doing much to control the application rate. Once the clutch has applied though, the additional pressure of extra return springs is negating that same amount of some of the hydraulic apply pressure. So, in a static applied condition, given a certain hydraulic apply pressure and torque input value, the clutch with the heavier return springs will have the tendency to slip before the clutch with the lesser amount of return springs.
I think I just confused myself, sorry.

 

[Alky V6]

The apply piston will begin to stroke at a higher hydraulic pressure value, but that doesn't necessarily mean that the clutch plates are applying any more quickly, since accumulation, if any, and feed orifice size are still the larger part of how quickly a clutch pack applies.

 

[Alky V6]

In a racing transmission there is normally no accumulation and large feed orifices are used. I can see where a higher return spring load would tend to cause a clutch pack to lock up sooner, if the clutch pack has a lot of over capacity. Even at that, the difference would be so slight, I don't believe it would be detectable.
A clutch pack that has a borderline torque capacity may slip a little longer at the end of the piston stroke since the overall application pressure is topping off at a lesser value due to heavier return springs.

 

[chris718]

There are situations where a lack of accumulation or absence of an accumulator cause the shift to be softer.In a 2004r you get a harder 1/2 shift with the accumulator feed restricted but functioning than with a blocked accumulator .However this causes other concerns.I have tuned my units to work without the accumulator by using a 3.005" intermediate servo piston.On a 400 the lack of an accumulator w/ 3 return springs is exactly the same.I like to use 12 return springs and no accumulator with a fixed line pressure.The less grab a particular clutch has the more time the shift will take from start to finish especially when the pressure rise in the given circuit is lower than the feed pressure.There is a bleed hole in the center support that is not at the highest point in the circuit.This means not delaying the pistons accelleration off the support until the air has been burped out and the circuit has filled will result in a lower apply pressure.If you can pump up the piston during an air check with 25 psi of air you can bet your life if there isnt enough spring pressure the piston will be at almost full travel below 100 psi .Under wot loads,with an improperly timed circuit,the bang at the end of the shift is usually the result of a slipping clutch and the sudden apply after max pressure has been reached.

 

[chris718]

In a racing transmission where there is normally no accumulation and large feed orifices are used. I can see where a higher return spring load would tend to cause a clutch pack to lock up sooner, if the clutch pack has a lot of over capacity. Even at that, the difference would be so slight, I don't believe it would be detectable.
A clutch pack that has a borderline torque capacity may slip a little longer at the end of the piston stroke since the overall application pressure is topping off at a lesser value due to heavier return springs.

Listen up.There is a detectable difference I have done back to back testing ripping my hands and knuckles apart for the last 20 something years researching this stuff.You are being given free information to tests that you probably dont have the time to perform.If you want to dismiss them ,go aheadAnd once again,I am in no way trying to be a jerkoff to you.These things are universally accepted,it isnt just me who understands them.

 

[turbobitt]

Listen up.There is a detectable difference I have done back to back testing ripping my hands and knuckles apart for the last 20 something years researching this stuff.You are being given free information to tests that you probably dont have the time to perform.If you want to dismiss them ,go aheadAnd once again,I am in no way trying to be a jerkoff to you.These things are universally accepted,it isnt just me who understands them.

Just to thow in my 2 cents. I personally don't think 3 or twelve springs make any difference. The springs are simply not big enough to make any significant difference. But then again It's not like I done a lot of back to back comparisons with any instrumentation.

Allan G.

 

[Alky V6]

Listen up.There is a detectable difference I have done back to back testing ripping my hands and knuckles apart for the last 20 something years researching this stuff.You are being given free information to tests that you probably dont have the time to perform.If you want to dismiss them ,go aheadAnd once again,I am in no way trying to be a jerkoff to you.These things are universally accepted,it isnt just me who understands them.

All I can tell you, Chris, is that I have been moving up with the number of return springs in the intermediate with my car over the years and have not been able to notice any difference. Not feeling it in the seat, and not seeing it in the datalogs.

 

[chris718]

Just to thow in my 2 cents. I personally don't think 3 or twelve springs make any difference. The springs are simply not big enough to make any significant difference. But then again It's not like I done a lot of back to back comparisons with any instrumentation.

Allan G.

The springs I use I had made 25% stiffer and they make a big difference.Its incredible,the shift is FASTER,but the bang at the end went away.

 

[chris718]

All I can tell you, Chris, is that I have been moving up with the number of return springs in the intermediate with my car over the years and have not been able to notice any difference. Not feeling it in the seat, and not seeing it in the datalogs.

What are you trying to accomplish?Is the shift not what you want or you just want to experiment?There are many ways to change thins and many things about the shift you can change.Just need to know what you are after.

 

[Alky V6]

What are you trying to accomplish?Is the shift not what you want or you just want to experiment?There are many ways to change thins and many things about the shift you can change.Just need to know what you are after.

I was trying to soften the tail end of the shift where the tires would tend to start slipping uncontrollably.
The new engine may change things, so I'm not planning on making any changes until I see how things run.

 

[chris718]

I have the springs when and if you decide to try them.Also you need to use a wave plate or wave plates.More excerps from my book:

NOTE
When discussing the components of the intermediate clutch pack the terms “friction” and “clutch” are used and both refer to the same items. This is also true for the terms “steel” and “steel plate”. A certain pattern of word usage has developed in the trade using either term to refer to the same item. It seems to be loosely based on learned behavior or a dependence on other words it is used with. This doesn’t follow any pattern I am aware of but I thought it worthwhile to mention. Also when discussing the intermediate clutch pressure plate the “face” is what is visible when it is in position in the case and being viewed from the pump bore, and the “work surface “ is the area that the clutch contacts.

The early design intermediate clutch pack (1991-1995) uses four .085 paper based frictions and four .080 steel plates. The pressure plate measures .375”. We will refer to this pressure plate as the early pressure plate.The approximate overall height of this pack is 1.035”. The late design intermediate clutch pack (1996 and up) uses the same steels and pressure plate as the early design but uses four revised .070 high energy frictions and a wave plate was added. The thinner revised clutch plates made room for the .075” wave plate and their high energy lining is superior to the original design.The approximate overall height of this pack is 1.070”. There is also a late pressure plate used on 97 and up transmissions. This pressure plate measures .280”. This pressure plate has a different profile and no counterbore in the face and will not fit into a ’96 and down case. Upon inspection you will sometimes find the face of this pressure plate to have grooving or scoring from making contact with the direct clutch drum. This is caused by the direct drum running off center and insufficient clearance between the plate and drum. Always use the thickest intermediate clutch snap ring that fits in the groove in the case with this type of pressure plate. This will reduce plate travel and increase operating clearances between these two items. If the face is scored it can be reused as nothing else in the transmission relies on that surface.


Before we get ahead of ourselves explaining components of the clutch pack lets look at the intermediate sprag.The type of intermediate sprag we use will dictate the components we select for the intermediate clutch pack. In general the 34 element intermediate sprag can be reliable up to 700 foot pounds of torque if using the methods discussed in this manual to maximize its power handling capability. Anything above this should consider the use of an updated 36 element sprag and drum assembly. There are exceptions to the rule and they are covered in the chapter on the direct drum. If a 34 element sprag is to be used with 500+ foot pounds of torque or a valve body with fixed line pressure, intermediate clutch pack selection becomes critical to sprag longevity. The following changes must be made to reduce the load placed on the 34 element sprag during a 1-2 ratio change. Failure to do so will almost certainly result in sprag failure. If you are working with an early transmission that is not equipped with a wave plate, it should be updated. Source a new or used wave plate and late style intermediate clutch piston. If you have access to a lathe, you can modify the early piston to accept the wave plate. This is covered in the”INTERMEDIATE CLUTCH PISTON” section.

It is highly recommended to use 3 stock TH400 paper based frictions. These frictions feature a waved steel core that will cushion the load placed on the sprag and reduce shift shock. The clutch measures .085” thick but the overall height is approximately .110” because of the waved steel core. The steel plates measure.100”. The pressure plate measures .440”. The approximate overall height of the pack is 1.070”. These parts are fully interchangeable up to 1996 units, but the pressure plate cannot be used on 97 and up units. Do not worry. By using the thinner 4L80E steels they can be made to fit 1997 and up units.. This will all be covered during assembly. Please note, that some TH400’s were assembled with a waved steel on top of the piston instead of a flat steel. If you are pushing the limit of the sprag, it is highly recommended to use this wave plate on top of the 4L80E wave plate. If the transmission will be assembled with a custom 36 element sprag and drum assembly the late design intermediate clutch pack can be used. Remember that this clutch pack uses 4 high energy clutches and they are flat ,not waved The shift will be more aggressive than with the TH400 style clutches. If the shift is too aggressive the TH400 clutch pack can be substituted. Further fine tuning of the clutch pack can be done by using wave plates, a combination of waved and flat clutches, or changing the orifice that feeds 2nd clutch oil to the clutch pack.

 

[turbobitt]

Yes.
I'm referring to the later high energy frictions, like what comes in the 4L80E. I certainly am NOT referring to the old waffle style frictions from decades ago (1960s or 70s) that were also greenish in color.

Don, is there a way to identify these plates ? I have a stack in my stash because I was thinking of testing these some day. Within my stash, the stack of plates are separated in three populations and have three different P/N's.

646,B2245-F
646,B1809-J
646,B1658-D

They all look the same and the frictions look to be made of three sections per side with an interlocking puzzle looking feature to hold them together during manufacturing.

Allan G.

 

[Alky V6]

Don, is there a way to identify these plates ? I have a stack in my stash because I was thinking of testing these some day. Within my stash, the stack of plates are separated in three populations and have three different P/N's.

646,B2245-F
646,B1809-J
646,B1658-D

They all look the same and the frictions look to be made of three sections per side with an interlocking puzzle looking feature to hold them together during manufacturing.

Allan G.

Sorry, Allan. I don't have a clue.

 

[Alky V6]

I have an old tool that I used to use to put wave into some import transmission friction plates. It actually worked very well to soften the shifts on certain applications. I may have to dig it out and give it a try on the 4T80E frictions.

 

[matt69olds]

Greetings Chris! How close are you to having your TH400 manual ready for sale?