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Discussion Starter #1
Hey everyone,
I was driving to Indy this morning to pick up a few parts, Started rolling into the trottle and POP!! I lost O/D thought that was it then I stopped at a gas station. Went to leave and found out I also lost reverse. Truck shifts perfect 1st-3rd just no overdrive or reverse. Any ideas before i pull the trans.
Thanks, Jared
 

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Discussion Starter #2
I really need help guys!!
 

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Don't worry, it will be apparent by the time you get to intermediate shaft during teardown. Splines or shaft failure.
 

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Discussion Starter #5
well I got the trans out and the front pump taken out along with the direct clutch were i thought my problem would be, And it looks brand new...so If anyone else has any ideas throw em on the table!!
 

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Which direct clutch did you look at?
The OD Direct(in the OD unit)?
Im betting your problem is somewhere in the OD unit...
When you say you don't have OD, do you lose motion like the truck is in neutral or does it just feel like its still in 3rd?

Im almost done doing an overhaul of my OD unit. When Im done, Im going to write up a "how to" to help show everyone. I guess my response to this thread will serve as part of the writeup.

NOTE: All parts I refer to in this section are in the OD unit. The transmission has two sections. It is essentially a 3 speed transmission, with an OD box literally hanging off the back end. Imagine your favorite 3 speed tranny, and remove the tailshaft housing. Install a piston around the outputshaft which will be used to engage/disegnage overdrive. Rename the output shaft the intermediate shaft. Install a gear onto the end of intermediate shaft, and put some internal splines for a clutch pack on the tailshaft housing and call it an OD housing.


Here is a thing I wrote a few weeks ago to understand what goes into OD operation:

3rd engaged:
Intermediate shaft is turning clockwise, which is splined to the overrunning clutch and planetary.

During regular power transmission in 3rd, power is transmitted from the intermediate shaft to the planetary. The Planetary turns the sun gear, which is splined to the sliding hub. In 3rd with no OD piston pressure, spring pressure applies the direct clutch packs which are splined to the sliding hub. The direct steels transmit power to the direct drum. The direct clutch drum is splined to the annulus gear, which is splined to the output shaft.

Between 3-4 shift, after the direct clutch disengages and before the overdrive clutch engages, power is transmitted to output shaft directly through the overrunning clutch.

After the 3-4 shift:

Overdrive steels are splined to the case; the overdrive clutches are splined to the sliding hub. With the overdrive clutch engaged, the sliding hub stops turning, which is splined to the sun gear which also stops turning. Direct clutch is disengaged, allowing the direct clutch drum, annulus and output shaft to spin at a different rate from the sun gear and sliding hub.
With the sun gear not rotating, power is transmitted from the intermediate shaft into the planetary gear set. Since the sun gear is held stationary, the annulus begins to turn at a faster rate, spinning the direct drum(which spins the disengaged direct clutch steels), as well as the annulus gear turns the output shaft. Over running clutch is overrunning.

So basically in 1-3rd, as far as the OD unit is concerned, your power flow to the rear wheels occurs in one of two ways. From the intermediate shaft through the Planetary to the sun gear, to the sliding hub then the direct clutch frictions which tranfer power to the the direct steels that transmit power to the direct drum then to the annulus gear then to the output shaft.
The Annulus gear is where the planetary spins inside of. So if the direct clutch is engaged, the sun gear and annulus gear(which is splined to the output shaft) it all turns 1:1 and the planetary gears just go along for the ride.
Note what i said about the 3-4 shift period, where the direct clutch is disengaged before the OD clutch is engaged. At this point there would be no power transmission from the intermediate shaft to the output shaft if it wasn't for the overrunning clutch. The overrunning clutch hub is just behind the planetary gears, and they ride on the same splines on the intermediate shaft. When the direct clutch disengages, the overrunning clutch(which is like a freewheel on a bicycle) locks in, and transmits power to the output shaft.

If you didn't want OD, you could remove all of the OD direct clutch components and the truck would still have 1-3, because power would go through the over running clutch directly from the intermediate shaft through the overrunning clutch hub through the rollers to the shell of the output shaft.

BUT, you wouldn't have reverse. The overrunning clutch being a freewheel, freewheels any time the output shaft spins faster than the intermediate shaft in a clockwise direction(looking at the rear of the vehicle). Its purpose is to allow the output shaft to spin faster than the intermediate shaft when in OD. However, if the direct clutch failed and the vehicle was relying on the overrunning clutch to move, when you put it in reverse, the intermediate shaft spins backwards which is the same effect for the overrunning clutch as the being in overdrive, and the overrunning clutch freewheels.

Something is broken in the OD unit area. I wouldn't even say worn was the main failure(although its possible something worn led to a catastrophic failure of a part) because of the bang you mentioned. The bang or pop was some component saying I had enough in the powerflow of the direct clutch assembly.

I wouldnt be suprised if it was a planetary, sun gear, or OD clutch issue.
Also look at your spring plate for the OD direct clutch. Mine was getting wallered on the ID.

heres some pics..

Here is the spring plate I was talking about. The Sun gear is beind it, and this plate slides over the straigh splined section and seats against the sun gear splines(angled splines) and is retained with a snap ring. See how the splines for the sun gear were cutting into the spring plate?



When assembled it looks like this:


This is the OD Drum, Annulus Gear, and Output shaft assembly. All these peices are splined together.



Inside of the Drum/Annulus Gear/Output shaft looks like this:

NOTE, in ALL of these pictures, there are a pair of snap rings which are reversed. See the flat snap ring down by the gear teeth, and the round snap ring at the top of the drum? I have those backwards and had to tear down the assembly after I had it put together. The round snap ring should be at the bottom and the flat one should be at the top!



This is the overrunning clutch, or sprag.


Here is the overrunning clutch slid onto the over running clutch hub and torrington bearing.


It gets slid into the smooth bore of the output shaft, compare to the empty picture of the output shaft.



As you can see in the last picture the outer edge where the rollers ride is ramped. If you rotate the hub clockwise, the rollers ride up the ramp and become wedged into the bore of the output shaft, and transmit power. However, if you were to turn the hub counter clockwise(vehicle in reverse), or the hub stationary and spin the drum clockwise, the rollers will roll down to the bottom of the ramp and allow the clutch to freewheel. Neat huh?
So if your direct clutch components or planetary were to go out, this is what would give you forward motion.

Next the planetary gets dropped in.. The ID of the plantary is also splined to the intermediate shaft. At this point in time, if you spun the input shaft, the planetary would do nothing, since there is nothing retsraining the planetary gears. If the sprag was not there, the planetary would just spin inside of the annulus gear.


Next goes in the sun gear with the spring plate, thrust bearing. Now if the intermediate shaft was to spin, (and the sprag wasnt there) The intermediate shaft would spin the planetary gear set inside of the annulus gear, and the reaction of the plannetary gears rolling inside of the annulus will cause the sun gear to turn.



next to go on is the Sliding Hub, or OD Direct clutch hub and spring. This will later be compressed down over the sun gear. If it was, and the above happened, now the direct clutch hub would turn with the sun gear.


Heres the OD Direct clutches installed, before the spring is compressed dropping them down into the drum. As you can see, if it was compressed down into the drum, and the intermediate shaft was turned, as per above writeup the hub will turn which is splined to the frictions, which would transmit the power to the steels, which transmits power to the OD of the drum.


Here is the assembly after the spring is compressed, and the snap rings are in place. At this point, the big spring is loading the OD direct clutch, making this assembly essentially locked as one big unit. To release the OD direct clutch you would have to press down on the top of the hub, compressing the spring and releasing the OD direct clutches.


I didnt inlcude the pictures(but do have them) of dropping this assembly into the OD housing. The following picture is simply after this assembly was inserted into the OD case housing. In this picture I am doing the first next step, installing the OD clutch retaining ring.



Then the OD wavy spring:


Then the OD clutch pressure plate:


Then 5 frictions and steels, followed by the retaining ring:


So as you can see, since the OD cluctch frictions are splined to the hub, and the OD cluch steels are splined to the case, if you were to push push down on the OD clutch pack, it would STOP the OD direct hub, which would essentially lock up the trans like a big brake.

The OD piston as it pushes down on the OD Clutch pack, it also pushes down on the hub, which compresses the OD Direct spring, which releases the OD direct clutches. So the hub stops, and so do the frictions of the OD direct clutch, and so does the sun gear. The planetary continues to rotate at intermediate shaft speed, and the annulus gear is spun at a faster speed through the planetary rollers maing the annulus gear, direct clutch drum, direct clutch steels, and output shaft spin at OD speed.

Sorry I dont have a smoking gun for you, but hopefully this helped you understand what the key components are in the OD unit, where the power flows through at different times, and therefore help you diagnose at tear down.
 

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did you use a dummy shaft when assembling ?
 

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nope. not shown in these particular pics but i eyeballed it and kept an eye on it and after i finished assmbling the direct clutch pack i slid it on the intermediate shaft to ensure the splines were lined up
 
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