Can I run dex6 in my th400.

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So my th400 lost reverse so I am rebuilding it. I was running dex3h because I read online a few people had problems running dex6 and reverting back to dex3 solved them. Anyway because the transmission will be fresh should I run dex6? Any things I'm overlooking such as clutch compatibility or seal compatibility. It will have stock tan Borg Warner frictions. Thanks
 
I'd run DEX6 only if you want the longer drain interval myself. Considering those have a kick down switch and obviously no computer control most of the shift timing and firmness comes from what you did in the rebuild.

I ran DEXIII H in my 200R, all the kick down and shift firmness was driven by the TV cable setup.

I have even seen guys swear by running TYPE F in those.
 
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DexronVI has almost the same frictional properties as DexronIIIH but the starting viscosity is lower.

If the transmission is okay with lower shear stable fluids it should be fine but if you want a high viscosity synthetic replacement I would use my Mobil 1 ATF or Redline D4
 
Or, if you want a slightly thicker Dexron III type fluid you could use the Redline D4 or the Amsoil ATF.
 
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Already used amsoil before and I really like it but this is an old plow truck that has seen 10,000 miles in the last 4-5 years. Basically looking for whatever is the cheapest that will work good.
 
Originally Posted By: joegreen
So my th400 lost reverse so I am rebuilding it. I was running dex3h because I read online a few people had problems running dex6 and reverting back to dex3 solved them. Anyway because the transmission will be fresh should I run dex6? Any things I'm overlooking such as clutch compatibility or seal compatibility. It will have stock tan Borg Warner frictions. Thanks


On a rebuild with new seals, Dex VI will work fine.

If you need any help on the build let me know.....I know LOTS of tricks.
 
Originally Posted By: clinebarger
Originally Posted By: joegreen
So my th400 lost reverse so I am rebuilding it. I was running dex3h because I read online a few people had problems running dex6 and reverting back to dex3 solved them. Anyway because the transmission will be fresh should I run dex6? Any things I'm overlooking such as clutch compatibility or seal compatibility. It will have stock tan Borg Warner frictions. Thanks


On a rebuild with new seals, Dex VI will work fine.

If you need any help on the build let me know.....I know LOTS of tricks.

Thanks. I'm just going to dual feed the direct clutches and make sure everything else is in spec per the atsg manual. If I have any questions ill let you know.
 
Originally Posted By: bigt61
Originally Posted By: andyd
Head for Wal Mart and find Super Tech Dex-Merc in gallons
Agree


agreed here as well.

I use Wal-Mart's Dex3 in my plow truck (700r4). it will serve you well.

I put a cheap drain plug on the pan and I drop 3-4 quarts every year or two.
A few years ago I syphoned out as much PS fluid as I could and used the Dex3 in there as well.

Mine doesn't see 100 miles an a year, and I don't think it's seen 1,000 miles since I bought it
smile.gif
 
Originally Posted By: joegreen

Thanks. I'm just going to dual feed the direct clutches and make sure everything else is in spec per the atsg manual. If I have any questions ill let you know.


I wouldn't dual feed the directs on a plow truck, It only increases clamping force in third gear & actually slows reverse apply which is not good for plow duty. This is a high performance mod not a heavy duty mod.

ATSG manuals don't cover Front to Rear Carrier (Planet) end-play, Spec is .008"-.015".
Install the output shaft in a vice like shown & assemble up to the center support, While holding down the center support, Lift up on the front carrier like shown.....This is your end-play, Use these shims under the thrust washer that sits between the 2 carriers...... End Play Shims
You can also use these shims to set "Rear Unit End-Play" by using them on top of the 4-tang thrust washer at the output shaft.(IF you don't "Rollerize" the output shaft!)



 
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I do recommend "rollerizing" between the output shaft & case, This will eliminate the 4-tang thrust washer & 3-tab selective washer & a lot of friction.

You will need.....
TH350 Pump to Direct Drum torrington bearing.
TH350 front end-play shims.
'91-'96 4L80E Pump Bushing.

Measure the thickness of the original Selective & Thrust Washer when stacked together with a caliper, This measurement will be used for 2 purposes....
1. This will give a calculation for the Maximum amount the Case Bushing can protrude above the back of the Case.
2. Starting point for setting Rear unit End-play, Add .010"-.020" to the measurement & start there with the Bearing & Shims. Let's say the original selective & thrust measures .140", Start with the Bearing & Shims at .150" to .160" thick.

A 4L80E Pump Bushing is twice as wide as a TH400 Case Bushing, Giving better support & you can leave it protruding out of the case to center the Bearing, Again let's say your original selective & thrust measured out at .140", Leave the bushing protruding .120"-.130" (.010"-.020" less) to clear the radius on the output shaft & provide adequate lubrication to the bearing.
Set Rear Unit End-Play to .005"-.010", With the bearing.....You can run tighter end-play than factory spec!

The first pic is of the TH350 pump bearing & Shims (TOP), & original TH400 selective & thrust (BOTTOM).

Second is comparing a 4L80E pump bushing to a TH400/4L80E case bushing.

Third is of a 4L80E Pump Bushing installed in place of the original Case Bushing, Shims....Then Bearing.
I was test fitting the bearing to make sure I didn't "Bell" the bushing.....Black side goes DOWN during final assembly!!!!

Forth is checking rear end-play on a 4L80E, Same procedure on a TH400. Set the dial indicator to zero & lift up on the output to check.







 
So I managed to save 8 quarts of the old ATF. Can i strain it out really well and reuse it? The fluid is not that old and doesn't have alot of miles on it. Also trans temps never get much higher than 200f when plowing.
 
The truck is not a dedicated plow truck it's my daily driver. I only plow a few driveways when it snows. Everywhere I read that the dual feed mod is good. What are some reasons I shouldn't do it?
 
Originally Posted By: joegreen
So I managed to save 8 quarts of the old ATF. Can i strain it out really well and reuse it? The fluid is not that old and doesn't have alot of miles on it. Also trans temps never get much higher than 200f when plowing.


I would not.

It doesn't make sense to contaminate new parts with questionable ATF. One cannot go by sight (Visual Clues) to determine fluid condition.
 
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Originally Posted By: clinebarger
I do recommend "rollerizing" between the output shaft & case, This will eliminate the 4-tang thrust washer & 3-tab selective washer & a lot of friction.

You will need.....
TH350 Pump to Direct Drum torrington bearing.
TH350 front end-play shims.
'91-'96 4L80E Pump Bushing.

Measure the thickness of the original Selective & Thrust Washer when stacked together with a caliper, This measurement will be used for 2 purposes....
1. This will give a calculation for the Maximum amount the Case Bushing can protrude above the back of the Case.
2. Starting point for setting Rear unit End-play, Add .010"-.020" to the measurement & start there with the Bearing & Shims. Let's say the original selective & thrust measures .140", Start with the Bearing & Shims at .150" to .160" thick.

A 4L80E Pump Bushing is twice as wide as a TH400 Case Bushing, Giving better support & you can leave it protruding out of the case to center the Bearing, Again let's say your original selective & thrust measured out at .140", Leave the bushing protruding .120"-.130" (.010"-.020" less) to clear the radius on the output shaft & provide adequate lubrication to the bearing.
Set Rear Unit End-Play to .005"-.010", With the bearing.....You can run tighter end-play than factory spec!

The first pic is of the TH350 pump bearing & Shims (TOP), & original TH400 selective & thrust (BOTTOM).

Second is comparing a 4L80E pump bushing to a TH400/4L80E case bushing.

Third is of a 4L80E Pump Bushing installed in place of the original Case Bushing, Shims....Then Bearing.
I was test fitting the bearing to make sure I didn't "Bell" the bushing.....Black side goes DOWN during final assembly!!!!

Forth is checking rear end-play on a 4L80E, Same procedure on a TH400. Set the dial indicator to zero & lift up on the output to check.



Super Cool.

Thanks for the picks and instructions.

The tranny shop I work with always recommends "rollerizing."

And believe me, we have a lot of older PU trucks that have been converted to snow plows. They tell me the average mileage before conversion and upgrade is around 225,000 miles.
 
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Originally Posted By: joegreen
The truck is not a dedicated plow truck it's my daily driver. I only plow a few driveways when it snows. Everywhere I read that the dual feed mod is good. What are some reasons I shouldn't do it?


I was under the impression that it was a dedicated plow truck.

The slower reverse apply is my biggest concern, Just be patient & let it latch up before applying throttle.

During full throttle 3-1 & 3-2 automatic/forced downshifts, The direct piston return springs are not strong enough to return the piston in a timely manner because it's trying evacuate 200% more ATF than the circuit was designed to evacuate, Over time this WILL distress the direct frictions.
I HIGHLY recommend "High Rate" return springs in any dual feed hydramatic transmission..... Return Springs

For high RPM use (Above 5500), A .030" bleed hole is required at the edge of the direct drum to prevent "centrifugal apply" of the direct clutches it 1st gear when the direct drum is overruning at over 80% of input RPM, This is probably not a concern for you.

Dual Feeding the directs is a fantastic modification.......On rigs making north of 450 horsepower!! I rarely do this mod on a heavy duty unit, It is just not warranted.
 
Originally Posted By: joegreen
So I managed to save 8 quarts of the old ATF. Can i strain it out really well and reuse it? The fluid is not that old and doesn't have alot of miles on it. Also trans temps never get much higher than 200f when plowing.


Stop by your local Napa and see if they can source some Peak ATF for you since they have it on clearance right now:

https://www.napaonline.com/en/p/PMRATFUNIV

Don't get your hopes up that they can get it for you but you never know till you try.
 
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Thanks for the info on the atf. Ill run by my napa tomorrow and see whats up. As far as the dual feed mod you have convinced me not to do it. Also I am trying to do this rebuild on the cheap. Is it really necessary to rollerize the tail shaft?
 
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