904 Transmission Stopped Going Into Gear

[CudaFactHackJob]

I guess you missed my post on Sept 10 where l said to install the drums without clutches, no band, and no pump oring. That's to check end play. Grease the fiber washer into place in the front of the forward drum or it could drop out and cause this problem of no endplay.

 

[Duster Captain]

I'm pulling it all apart and will try assembling without clutches, band, and o-ring and will post pictures hopefully later today.

 

[Duster Captain]

This is what the guts look like with the following conditions:

-no frictions or steels in either drum
-no band on direct drum
-no oring on pump
-pump bolted in to torque spec (175in-lbs)
-thrust washer greased in place between input and output shafts
-fiber thrust washer greased in place on front of forward drum

In this state there is a gap as shown in the tabs on the sun gear shell and the input shaft is too tight to turn by hand and has no measurable end play.

When I loosen the the pump bolts just a little bit, the input shaft spins nice and easy and I start to get some endplay.

What am I doing wrong?

 

[CudaFactHackJob]

First of all; never tighten the pump bolts if the input shaft won't turn. We tighten them gradually; making sure there's no binding. Do you have only one thrust washer on the front of the output shaft, one between the drums, and one on the back of the pump? Check the direct rings to make sure they're interlocked or maybe remove them for the end play check. The drum tabs don't interlock completely, but those look a little too far forward; not interlocking quite enough; maybe another 1/16" at least. If it all looks good, remove the output shaft washer and try it as a test. Is the tailshaft housing installed and the lock ring clicked into place on the output shaft bearing? Got a pic of the lock ring with the cover off? The one under the mount.

 

[Duster Captain]

I took everything apart and took a picture at every step, let me know if anything looks wrong.

Both rings and one thrust washer on back of pump. Rings are both locked and everything looks fine. Pump slides into direct drum smoothly.

Thrust washer in forward drum.

View once forward drums are removed. Original shaft thrust washer is held in place with grease.

Removing front planet assembly. Thrust washer greased in place.

Removing shell. There is a steel ring on back of shell. The rear planet thrust washer is held in place with grease.

Looking into rear ring/reverse drum.

Rear ring removed.

Extension housing is attached to case, this is a pic of the output shaft bearing retaining ring. It looks fully seated in the groove which is biased towards the front of the transmission.

When I install everything (with no frictions, forward band, or pump o-ring), the input shaft spins freely and has some endplay until I start to snug the pump bolts . If I get the pump bolts snug or tight, the input shaft is not free to turn by hand and there is no endplay....

Does anyone see anything missing/wrong so far?

 

[CudaFactHackJob]

Is the rear band tight not allowing the drum to move all the way rearward? How much clearance is there under the snap ring on the front of the output shaft? Is the rear bearing seated fully into the tailshaft housing? Are the pump halves aligned? How much endplay does the output shaft have as it is right now?

 

[Duster Captain]

I will investigate these things and report back.

 

[Duster Captain]

Results of more investigation:

I did reassemble the pump with an alignment clamp.

The rear band is loose enough to let the reverse drum move by hand. I can push it to the rear and feel it solidly bottom out against the inside of the case.

I removed the speedometer gear and looked at the rear bearing. It looked fine.

For fun, I took the entire tailhousing off and tried reassembling the drums.

I think I found the problem, see video below.



These are the conditions in the video:

-Tailhousing off (obviously)
-No clutches in any drums
-No direct drum band
-No bump o-ring or gasket
-Retaining clip on output shaft installed (feels fairly snug in its slot)

Is there supposed be this much end play at this point?

When I assemble the drums while the trans is in this state, it all goes together and when the pump is tightened, the input shaft spins freely and has endplay. However, if I slide the tailhousing on and tighten its bolts, the input shaft no longer spins freely or has endplay. Everything gets "bound up" again.

So it has something to do with the input and output shafts getting pressed together too hard when the pump pushed the input shaft back and the tailhousing bearing pushes the output shaft forward?....

 

[CudaFactHackJob]

Yes, that much end play in the rear shaft is normal when the tailshaft housing is removed. I think the rear bearing is not seating all the way into the tailshaft housing. Or the bearing is not seated onto the output shaft. I paused the video but it got too blurry to tell. Look inside the tailshaft housing to see if there is a foreign particle embedded. The only reasons to remove the tailshaft housing is to check and clean the governor and replace the governor rings. If a governor is not stuck and the trans is starting off in first gear and shifting at all, I don't recommend the beginner to remove the tailshaft housing; not even the planetaries or even the little snap ring at the front of the output shaft. Just check the rear band by loosening the adjuster then reset it and leave it alone. Air check the servo. You could install the tailshaft into the housing then install them both together. Tap wherever you can to make sure the bearing is seated first.

 

[Duster Captain]

I verified that the bearing was properly seated on the output shaft and that the recess for the bearing in the extension housing was clean. See pictures.

I also took everything apart again and put the output shaft into the extension housing on its own making sure the bearing fully seated. Very hard to see but the bearing feels seated, I gently tapped the shaft with a rubber mallet to make sure nothing was loose. Picture below

I then put the shaft/ext housing sub assembly onto the main trans housing (while it was empty of all other parts). I made sure the shaft sealing rings properly slid into the shaft support and then carefully snugged the bolts in a cross pattern to full torque.

I then measured the end play on the front of the output shaft in this configuration and got .035". Anyone have any thoughts on that number?

I then started to reinstall internal parts.

When I got to the snap ring I made some measurements below:

The original snap ring is .050" thick. I am reusing it.

After the snap ring was installed I measured the gap under the snap ring. This was .013". Thoughts?

I installed the shaft thrust washer, front drums and pump (no frictions in either drum, no pump oring, no forward band) and began to torque the pump bolts. As before, the input shaft stopped spinning freely and had no endplay when the pump bolts were tightened.

I then removed the shaft thrust washer and reinstalled everything else and tightened the pump bolts all to spec in a cross patter and.....the input shaft spins freely!

For the record, I did previously try assembling everything with no shaft thrust washer to see if that was the problem and everything still got bound up, so I think I must have had something (ext hsg bearing?) not quite right and have now gotten it all right by taking everything apart and reassembling.

This is the drum engagement I get with the configuration I described above (no shaft thrust washer). Looks good to me.

The input shaft spins nice and easy by hand and I have .074" of endplay.

I measured my original thrust washer and it is .081"

Is this the cause of all my pain?

The input shaft endplay with no thrust washer is .074" and I am trying to put a .081" thrust washer between the shafts?

Is the solution just to get a thinner thrust washer? I would be very thrilled if that was my problem.

 

[CudaFactHackJob]

You still need at least .015 end play on a cold housing. The problem l see is that the direct drum is not engaging sufficiently into the sun gear shell when the output shaft thrust washer is installed. I don't suppose you could have accidentally installed two thrust washers between the forward and direct drum. The pump gasket will add end play.

 

[Duster Captain]

I only have the one thrust washer between the forward and direct drum. This is the washer we are talking about, correct?

The problem l see is that the direct drum is not engaging sufficiently into the sun gear shell when the output shaft thrust washer is installed.

I definitely agree that the direct drum was not engaging fully with the sun gear shell in my previous assembly attempt. But it looks to me like its going together correctly now.

This is my trans.

This is a reference picture from article on rebuilding a 1965 904 transmission from HotRod.com
Their direct drum engagement looks very similar to mine, am I missing something?

You still need at least .015 end play on a cold housing.

Could you elaborate a little on this? You're saying I need at least .015" of end play on the input shaft once the trans is fully assembled?

Shouldn't I be able to get any end play I want with the correct thickness shaft thrust washer? I have .074" of end play without any thrust washser. So can I just get a .060" thick thrust washer and end up at the required .015"?

I understand that the pump gasket will add a few thous of end play.

 

[CudaFactHackJob]

The only reason yours looks like the other one is because you have no button thrust washer. See, here's the question: Why would you need a thinner thrust washer now, but before that thrust washer was just fine? Stick a pry bar in the tailshaft snap ring access hole and try to push the bearing rearward. Note: Measure the thickness of the two front (larger) thrust washers and make sure they are within specs. I think the problem is in the back train; not the front. Once that is resolved, you will probably have an excessive amount of front endplay. Are all your thrust washers original? I still think the problem is in the back bearing.

 

[CudaFactHackJob]

Actually, it wasn't just fine before you even took it apart, was it; you had no end play. But was it ever determined why?

 

[Duster Captain]

Everything I can see about the rear bearing looks like it is correctly seated.

For sure it is correctly seated on the shaft. Its snug against the shoulder on the shaft and the lock ring is secured in as shown in the pictures. I also gently tapped the shaft into the housing and it felt fully seated. When I look through the snap ring slot and the speedometer assembly hole, the bearing appears fully seated in its recess in the ext housing.

The grey thrust washers both were .049" thick. on post #67

All washers are original.

I think I measured the pump thrust washer and not the forward drum washer because I did not disassemble the forward drum/input shaft sub assembly . I will investigate.

I still do not know why the input shaft had no endplay before I started disassembly. The root cause of the failure in my opinion, was the collapsed trans cooler line that caused the trans to fry. I have no idea what that did to the internals....

But in the end, if I get the proper end play on the input shaft and the direct drum is engaged properly with the sun gear shell and everything spins freely, I should be ok, correct?

 

[CudaFactHackJob]

I think there is a problem in the rear train. I wouldn't let something like this out of my shop. It would work but for how long? And why didn't this trans with no end play eat the thrust washers? I'm wondering if the governor support was damaged by that closed off line. Unbolt it from the case and take pics. Also of the output shaft where it rides in the governor support.

 

[Duster Captain]

I agree, something is not quite right still.

I think I discovered something else.

I took a closer look at all thrust washer thicknesses and compared them to the book:

-pump washer is .072" (book says it should be .061-.063") BAD
-forward drum washer is .071" (book says it should be .061-.063") BAD
-output shaft washer is .081" (book says it varies, could be .052-.085") Possibly OK

- both 3 tabbed thrust washers are .049" (book says they should be .048-.050")OK

I think I'll get 2 correct thickness washers for the pump and forward drum and then then see what the endplay is.

I will take another look at the output shaft support and shaft area.

 

[CudaFactHackJob]

But if that trans was operated with No end play then the thrust washers should absolutely be FRIED. Is there any sign of no lube on the thrust washer faces or the hard parts they contacted? Was a part of the band friction stuck between the drums? If your book and measurements are correct, where did .072 thrust washers even come from? Your pump washer looked like it had a wear line on it. Measure worn thrust washers on their thinnest point; not across the entire surface. Possible that the output shaft selective was chosen and installed correctly but using worn front thrusts which you may have inadvertantly flipped over. I'd put some play-doh or plasti-gauge in the ext hsg and then bolt it down over the bearing and see if it smashes completely. The compressed pump gasket is .015. I'm wondering what if you put a .052 on the output shaft and a .062 between the drums (total .040 less); will the direct drum then go far enough back into the sun gear shell to match the how-to pic? You could assemble it with the thin thrust washers and it would work, but if there's something in the rear train that is incorrect; it will eat itself up. Like if the support bearing isn't really seated but then becomes seated, your clearances will open up and thrust washer tangs could fall out of the holes.

 

[Duster Captain]

The thrust washers and mating surfaces do not look destroyed from no lube/heat. They look a bit worn but nothing terminal looking to me.

When I broke down the trans, there were chunks of frictions bands and grit from the frictions everywhere.

Its possible the collapsed fluid line happened at the end of the trans life, I have no idea.

I like the playdough idea, I will look at that.

I'm going to set the correct endplay with washer combinations and then see how it all looks.

 

[Duster Captain]

On that note, how do you disassemble the forward drum/input shaft?

Do I just remove the lock ring on the input shaft and tap the shaft and forward drum apart?

 

[CudaFactHackJob]

I wouldn't remove the forward drum from the shaft. Are the pump bolt holes squarely lined up thru both halves of the pump? Have you double checked the clutch clearance? I still don't see how this trans didn't fry the thrust washers. Did you see if they were flipped? I know you don't want to put this thing in and have problems.

 

[Duster Captain]

Wouldn't I need to remove the forward drum from the input shaft if I want to replace the thrust washer on it?

I aligned the pump hales by hand and eye, started all bolts by hand, then tightened the band around the halves before torquing to spec. It all looks aligned to me.

I currently have the frictions and steels removed, but the clutch clearances were within spec when I had everything installed previously. I will re-check it before final assembly.


What do you mean "check if the thrust washers were flipped"? Do you mean check if the tangs had been facing the wrong way on a planetary gear?

These two pictures show how I am assembling both thrust washers. Are you saying someone before me could have had them incorrectly installed?

I want to get everything right here, but at the same time if I get it to pass all final checks, its going in the car.

 

[CudaFactHackJob]

The composite thrust washers will wear on the outer surface and be stepped. The pump halves can be aligned and the bolt holes can still be off center. I don't understand the first sentence about the forward drum thrust washer.

 

[TrailBeast]

Wouldn't I need to remove the forward drum from the input shaft if I want to replace the thrust washer on it?

I aligned the pump hales by hand and eye, started all bolts by hand, then tightened the band around the halves before torquing to spec. It all looks aligned to me.

I currently have the frictions and steels removed, but the clutch clearances were within spec when I had everything installed previously. I will re-check it before final assembly.


What do you mean "check if the thrust washers were flipped"? Do you mean check if the tangs had been facing the wrong way on a planetary gear?

View attachment 1715230041

View attachment 1715230042

These two pictures show how I am assembling both thrust washers. Are you saying someone before me could have had them incorrectly installed?

I want to get everything right here, but at the same time if I get it to pass all final checks, its going in the car.

I seem to remember that some of the aluminum front planetary assemblies had a Torrington bearing where the sun gear butts against the inside of the planet gears assembly.
If this is the case you don't use a metal thrust washer between the planetary set and sun gear shell, as it will make your clearances too tight.
From what I can see in the first pic it doesn't have a Torrington bearing inside it.

I also remember there being multiple places the tangs of the washers would fit, but in some orientations they wouldn't sit flat like they should.
They had to be turned to find the right place where they sat flat.

 

[Duster Captain]

The pump halves can be aligned and the bolt holes can still be off center.

So how do you ensure that the bolt holes are centered on each other? Eyeball it while the pump halves are aligned with a clamp and then bolt the halves together?

I don't understand the first sentence about the forward drum thrust washer.

Basically how do you change out this thrust washer on the forward drum? It is free to slide around but is trapped between two parts in a way that I do not understand.