47re Clutch Pack Upgrades

Wanted to post a few pictures of some of the clutch pack upgrades that I recently performed on my 47re transmission. The most noticeable gains driving around with upgraded clutch packs are crisp-firm 2-3 shift and 3rd-overdrive shift.

Starting in the overdrive section of the transmission, there are two clutch packs: Overdrive/Direct clutch pack and the Overdrive/Brake clutch pack.

Overdrive/Direct
- Stock 47re clutch count is (10) double sided clutches for a total of (20) friction surfaces.
- This pack is engaged in gears 1, 2, 3, and Reverse. When the tranny shifts to overdrive, it releases this clutch pack.
- This pack is engaged with a large 820# spring, there is a sprag/overrunning clutch behind this clutch pack that prevents it from slipping in forward gears so failure in this pack will result in the loss of reverse and extreme wear and premature failure of the one-way overrunning clutch. In short this clutch pack is probably not that important to upgrade, but it's easy so I did it.

This is the clutch pack and the drums it engages. I built my own compressing tool to compress the heavy spring located under the center splined drum.


I decided to install a stock 48re clutch pack which includes (23) single sided friction/steel combo pieces or (23) total friction surfaces.



Picture of backside of same friction/steel combo piece


After installing the last steel/friction combo piece, you are left with a steel side facing up and the heavy steel reaction plate so common sense tells us this is one more place to add a two sided friction commonly found in a 47re.

Before double sided friction:

Double sided friction:


And after installing it, it looks like this:


That makes a grand total of (25) friction surfaces or a 25% increase in clutch capacity.

Now just compress the clutch pack and install the retaining snap rings and move on to the next clutch pack upgrades.

Overdrive-Brake Clutch Pack:
- This clutch pack is only engaged when the transmission shifts to overdrive.
- It's primary purpose is to act as a brake and stop the overdrive/direct drum so that power is routed through the overdrive planetary gears.
- These clutches are compressed with a hydraulic piston that is mounted between the main transmission case and the overdrive case.
- There are (5) frictions in the the stock 47re overdrive clutch pack.

Here is where the clutch pack resides, the frictions spline into the OD/direct drum and the steels lock into the aluminum transmission case itself. It's easy to see how when the pack engages, the clutches act as a brake and stop the direct drum. It should be noted that when the transmission shifts into overdrive the center drum slides down and compresses the spring and releases the OD/direct (25) clutches at the same time the brake clutch pack is engaged.


At the bottom of the clutch pack there are two snap rings, one is thick and one is a thinner and wider waved snap ring. In order to gain extra clutch pack space I only installed the thick snap ring. Pictured is the waved snap ring that I left out.


Here is a picture of the installed thick snap ring. If you look closely you will see the groove in the transmission case where both snap rings were originally installed and now just one thick snap ring is installed.


Next I installed a 48re used reaction plate. If you look at the pictures, you can see the stock thickness plate compared to the same thickness but stepped plate from a 48re, the used plate cost around $11.


Here is another picture of the 48re stepped plate. The plate is installed with the flat face up and the stepped face down onto the snap ring. This allows more clearance in the clutch pack.


By performing the two steps of discarding one snap ring and installing the 48re reaction plate, I was able to up the clutch count from stock of (5) frictions to (6) frictions for a 20% increase in clutch capacity.



And here is an up close view of the Overdrive brake clutch pack installed, notice how there is plenty of room to install the final wire-type snap ring that holds the pack in place.

:rockwoot:

We must collect all transmission upgrade info together


edit: I link the thread to 47RH/47RE Info/Do it yourself thread

subscribing

Moving on to the main transmission case, there are two clutch packs, one in front of the input shaft hub and one behind the input shaft hub. The one in front is commonly called the direct clutch and the one behind the shaft is commonly called the forward clutch. This terminology is a little confusing but the way I remember is the forward clutch is for forward movement and only disengages when in reverse.

Direct Clutch Pack:
- Has a smooth drum that is wrapped with the 2nd gear band.
- This clutch pack is engaged when the transmission shifts into 3rd gear.
- Stock 47re has (4) frictions in this clutch pack.
- Stock 48re has (5) frictions in this clutch pack.
- There are many different aftermarket drums, pistons, plates, etc for this clutch pack, it's probably the most modifiable pack in the transmission.
- This pack takes a lot of abuse especially on misadjusted transmissions because the 2nd gear band holds the drum stopped in 2nd gear and this clutch pack engages the drum and makes it spin in 3rd. Commonly there is a small bind-up on the 2-3 shift that really puts a lot of wear on this clutch pack, especially if the 2nd gear (aka intermediate) (aka front) servo is worn and leaky.
- Hydraulic pressure pushes a piston that engages this clutch pack.
- If the pump stator and or bushing in the drum is worn, hydraulics leaks cause a loss of pressure behind the piston making this clutch pack susceptible to premature failure.
- In short, if you do anything in your transmission, you should at a minimum upgrade this clutch pack.

The cheapest way to gain more clearance in this pack for additional frictions and steels is to install a different reaction plate. The stock reaction plate is about 0.280" thick. You can buy machined, stepped, altered plates for about $30, or you can buy a used pressure plate from the forward clutch pack for about $4.

In the picture below is the stock 0.280" reaction plate vs a used pressure plate from the forward clutch pack.


Upgrading this pack is really simple, you can use stock .085" thick frictions and steels and fit 1 extra friction and steel for a total of (5).
Or you can buy stock .070" steels and .065" frictions and fit a total of (6) frictions and (6) steels. If you really want to go extreme, you can fit (7) of the super thin alto frictions and (7) kolene .068" steels but those parts alone will run around $110.

For my truck, I installed (4) 0.065" frictions, (2) 0.085" frictions, and (6) 0.070" steels. There is a clearance specification for this clutch pack so depending on the make of the frictions, sometime you have to get creative with the thickness of the frictions and steels to make the clearance meet specification. On my 47rh transmission in my other truck for example, I used (3) 0.64" frictions and (3) 0.096" frictions with (6) 0.070" steels.

Then top off the clutch pack with the stepped used plate that came from a forward clutch pack pressure plate.


Then install the waved snap ring and verify proper clearance.


In this picture you can see the groove in the drum where the snap ring rides. Proper clearance for the clutch pack usually happens when the top of the reaction plate (used stepped forward clutch pressure plate I purchased for $4) is just below the bottom of the waved snap ring groove. As you can see in the picture, there is enough clearance and I of course double checked this with a set of feeler gauges.


For those wondering where to get different thickness steels and frictions, Wittrans.com has a great selection. Another bit of useful information is that the direct clutches and steels and forward clutches and steels are the same profile, just different thickness so they are 100% interchangeable. Typically the forward clutches are much thinner and therefore you can get more of them to fit in the direct drum.

Nice to see this all in one thread. What made you pull the trans already? Didn't you get the truck a month ago? LOL

Are you going to drill the holes in the forward drum for extra lubrication like you did in the Junker?

Big Blue24 said:

Overdrive-Brake Clutch Pack:
- This clutch pack is only engaged when the transmission shifts to overdrive.
- It's primary purpose is to act as a brake and stop the overdrive/direct drum so that power is routed through the overdrive planetary gears.
- These clutches are compressed with a hydraulic piston that is mounted between the main transmission case and the overdrive case.
- There are (5) frictions in the the stock 47re overdrive clutch pack.

Here is where the clutch pack resides, the frictions spline into the OD/direct drum and the steels lock into the aluminum transmission case itself. It's easy to see how when the pack engages, the clutches act as a brake and stop the direct drum. It should be noted that when the transmission shifts into overdrive the center drum slides down and compresses the spring and releases the OD/direct (25) clutches at the same time the brake clutch pack is engaged.

At the bottom of the clutch pack there are two snap rings, one is thick and one is a thinner and wider waved snap ring. In order to gain extra clutch pack space I only installed the thick snap ring. Pictured is the waved snap ring that I left out.

Here is a picture of the installed thick snap ring. If you look closely you will see the groove in the transmission case where both snap rings were originally installed and now just one thick snap ring is installed.

Next I installed a 48re used reaction plate. If you look at the pictures, you can see the stock thickness plate compared to the same thickness but stepped plate from a 48re, the used plate cost around $11.

Here is another picture of the 48re stepped plate. The plate is installed with the flat face up and the stepped face down onto the snap ring. This allows more clearance in the clutch pack.

By performing the two steps of discarding one snap ring and installing the 48re reaction plate, I was able to up the clutch count from stock of (5) frictions to (6) frictions for a 20% increase in clutch capacity.

And here is an up close view of the Overdrive brake clutch pack installed, notice how there is plenty of room to install the final wire-type snap ring that holds the pack in place.

Click to expand...

becarefull with the stepped plates if you run high line pressure. i have had a bunch of them bend to hell and back with around 195psi. they did it in street trucks and my old prostreet truck so i went to 1 snap ring and stock plate. i still was able to get 6 in there.

BigDodge said:

becarefull with the stepped plates if you run high line pressure. i have had a bunch of them bend to hell and back with around 195psi. they did it in street trucks and my old prostreet truck so i went to 1 snap ring and stock plate. i still was able to get 6 in there.

Click to expand...

Do you remember what thickness steels and frictions you used?

Man I would love to tear into an auto trannybut always been afraid and write ups like this make me want to try tear into one...

npe3484 said:

Do you remember what thickness steels and frictions you used?

Click to expand...

i think B/G clutchs only come in stock thickness. its like .065 i think.
on my drag race trannys i machine the OD housing so i can run 7 and 7 with stock bottom plate.

i will see if i can dig up some pics of the last one i did.

the tranny for my new toy has 5 in the front,8 in direct, and 7 in od. also i only run 5 clutchs in OD direct. it releases faster and helps let the OD brake clutch live longer. this is for a full drag race only. it will slip in reverse under load.

BigDodge said:

i think B/G clutchs only come in stock thickness. its like .065 i think.
on my drag race trannys i machine the OD housing so i can run 7 and 7 with stock bottom plate.

i will see if i can dig up some pics of the last one i did.

the tranny for my new toy has 5 in the front,8 in direct, and 7 in od. also i only run 5 clutchs in OD direct. it releases faster and helps let the OD brake clutch live longer. this is for a full drag race only. it will slip in reverse under load.

Click to expand...

Does the overrunning clutch wear out prematurely with just 5 OD direct clutches or do they hold up in the drag tranny?

When you put 8 clutches in the direct drum, are you running a milled down stock piston or did you machine a custom piston?

Forward Clutch Pack:
- This pack is located right behind the input shaft hub.
- Stock 47re has (4) frictions
- Stock 48re has (4) frictions with a different spline count so if you buy a 48re rebuild kit just remember to buy extra clutches for this pack that don't have the 93 center splines like the 48re clutches.
- This pack is applied in all forward gears and it's not a shifting pack so it's not subject to as much wear as the other packs.
- This pack is released when the transmission shifts into reverse.
- This pack is the most difficult one to upgrade since space is very limited.

I upgraded this pack from (4) frictions and steels to (5) frictions and steels for 25% increase in clutch capacity by purchasing a used forward clutch pressure plate and using it as a stepped reaction plate. This drums snap ring groove is machined a little tighter than the direct drum and it's nearly impossible to install the snap ring without grinding a little bit of the inner corner so the plate has a wider flat stepped portion for the snap ring.


The arrows point to the small corner than needs to be ground just a little to gain clearance for the wide snap ring. I just used a 4-1/2" grinder with a 1/8" thick metal cutting wheel and slowly made an approximate 0.030" deep cut and worked my way around the entire pressure plate. It is possible to install the snap ring without grinding the plate but makes the clutch pack a little tight which would cause it to drag a little in reverse, not a good idea for a daily driver that uses reverse regularly but running an unground/unmodified pressure plate hasn't been a problem for my drag race truck.



With increased line pressure, this pack seems to do fine with the stock (4) clutch count in 47re and 48re on diesel applications up to about 500 HP rear wheel horsepower, after that it's probably a good idea to upgrade this pack.

2nd Gear Band/Servo
- A servo pushes up on the apply lever to engage the second gear band.
- This band stops the direct drum to engage 2nd gear.
- Many upgrades are available for the servo, band, apply lever, strut, and anchor.
- Stock 47re has a 3.8 ratio on the band lever.

The best way to get increased holding capacity in 2nd gear is to increase the line pressure. Another common upgrade that installed on my transmission was the installation of a 4.2 ratio billet band lever. Non-billet levers are available in a few different ratios for around $20-30, billet levers run from $35-75. The main problem with stock cast levers is sometimes they break when line pressure is increased, in my transmission I went for the billet lever. Another common failure with increased line pressure is the band strut will bend. A few different heavy duty or billet struts are available for $15-30. And finally the cast anchor is also a weak point that can break when line pressure is increased, billet anchors run from $30-50. There is also a wide variety of bands available, flex bands in the $10-40 range and rigid bands in the $100-200 range. I only have experience using flex bands so I can't comment much on band selection. In my transmission I installed a Raybestos hi-energy flex band that cost about $16.

Another common upgrade is the servo that pushes the lever and tightens the band. In my transmission, I simply upgraded the servo cover with a oringed Sonnax cover. The cover does not help with the application of the band, it just helps make sure the servo disengages timely and smoothly by reducing hydraulic leaks. On the 1-2 shift, this servo extends and tightens the band, on the 2-3 shift, this servo collapses with the same hydraulic pressure that fills the direct drum piston to apply 3rd gear. With a leaky cover, the second gear band will still be applied while the 3rd gear direct clutches are applying causing a bind-up and premature wear in both the band and the direct clutches. This is also a common reason why some performance transmission builders choose the 4.2 ratio lever instead of the "Hemi" 5.1 ratio lever. The higher the ratio the longer it takes to release because the servo has to move farther to engage or disengage the band. Longer timing on release increases the chances of bind-up on the 2-3 shift. So on my build, I went with the 4.2 lever which increases capacity via leverage by 10%. I also built the tranny for increased line pressure so I installed a billet strut and a billet anchor.

Pictured is the billet 2nd servo cover, billet apply lever, billet strut, and ends of the band.


In this picture you can see the small but expensive billet anchor. The anchor is the part that connects to the other end of the band and is actually the part connected to the external adjustment screw.

BigDodge said:

becarefull with the stepped plates if you run high line pressure. i have had a bunch of them bend to hell and back with around 195psi. they did it in street trucks and my old prostreet truck so i went to 1 snap ring and stock plate. i still was able to get 6 in there.

Click to expand...

What were the symptoms of a bent pressure plate?

Big Blue24 said:

Does the overrunning clutch wear out prematurely with just 5 OD direct clutches or do they hold up in the drag tranny?

When you put 8 clutches in the direct drum, are you running a milled down stock piston or did you machine a custom piston?

Click to expand...

milled and turned TCS billet durm

npe3484 said:

What were the symptoms of a bent pressure plate?

Click to expand...

first thing it will burn up od clutchs quick.

BigDodge said:

i think B/G clutchs only come in stock thickness. its like .065 i think.
on my drag race trannys i machine the OD housing so i can run 7 and 7 with stock bottom plate.

i will see if i can dig up some pics of the last one i did.

the tranny for my new toy has 5 in the front,8 in direct, and 7 in od. also i only run 5 clutchs in OD direct. it releases faster and helps let the OD brake clutch live longer. this is for a full drag race only. it will slip in reverse under load.

Click to expand...

How did you manage to fit 8 of each in the direct drum?? And which drum are you calling the direct? The first or second one after the input shaft?

Good info, Thanks

npe3484 said:

How did you manage to fit 8 of each in the direct drum?? And which drum are you calling the direct? The first or second one after the input shaft?

Click to expand...

Direct is the forward most clutch pack.

Doesn't a stock 48RE have the 5.1 ratio lever?