D8K torque converter

[paul.walpole]

I have just rebuild my D8K ter and will be fitting it tomorrow. I have never build a CAT unit before and have a few questions.

The converter didn't fail, I had the trans go and though I would do the converter at the same time.

Firstly, the spit cone ball bearing. On assembly after tightening the nut that pushes the tubine in to the bearing inner race, I can still get some movement between the turbine and the housing. I removed and checked it 3 times comming to the conclution it is just bearing clearance. Is this normal to have play, say 1/2 mm. By thje way, all parts going back in (Bearing etrc are new)
The second issue I am having is with the tapered roller bearing. Both the cup and cone are wedged between retainers but there is nothing to pre-load this bearing. The converer once back together has excessive float forward towards the prop shaft (Tran end of the housing), so much the gear that drives the scavange pump rubs the outer housing. Can I assume that when it gets oil, the prssure pushes the turbine set back into the tapered bearing that will pre-load it?

Any help would be appreciated.

[bob]

Paul, I think something might be wrong from what you say here.
I will print out a cross section and bring home tomorrow night and we can talk about it.
Usually the ground shaft/sleeve that holds the stater solid also holds the turbine and impeller in place. The converter housing should never contact the scavenge pump gear.
Later Bob

[paul.walpole]

Hello Bob,

Thanks for replying.

The issue I am having is with the tapered roller baring. There is nothing to pre-load this bearing so you can move the stator in and out. One way it goes against the bearing and the other it bottoms against the converter housing where the shaft exists. I have been told today that the presure does the pre-loading. There is no radial movement, there are bearings as you say to the ground shaft but I am talking axial movement.

By the time you read this I will be putting the machine on a float. The converter is back in and all buttoned up. Just the cab tomorrow and forward sweeps so I am crossing my fingers.

The converter didn't fail previously and I have just put new bearings and bushes back in it so I cannot see how I would or could have gone wrong. I saw these issues as I was rebuilding it and subsequently pulled each section back appart and double checked. Then again as a tripple check. All work was done via the cat instructions to the letter. I just ended up shrugging my shoulders as every thing is how the book says, just loose.
I guess we will find out soon.

[edb]

Hi Paul,
yes, the thrust is taken on the roller bearing "after" the oil pressure builds up in the main T/Conv housing.
Until then the Conv hangs down on the taper of the bearings and the "back" thrust is taken on the faces between the main mounting hub and the outer (rear) face of the pump drive gear( at its inner diameter) just outside the step forming the seal ring tracks of the hub. Usually Galling-Adhesive Wear- takes place here on first start up if the flywheel housing is not prefilled with about 1-2 gallons of oil for lube of the components in here (we always lubed this area with Moly Lube) Also the scavange pump can fail at this time as it has no oil to pump until the Conv leaks enough for it to be able to pick up and pump.
If enough wear has taken place then the aluminium impeller and the pump drive gear will contact and leave the tooth impressions you saw, this can also happen if the scavange pump has failed and/or it has seized and the drive gear key has sheared and the gear has spun on the pump shaft.
Sorry I do not have a better pic of the area in question other than what I have attached below from my 1965 Powershift Transmission School at Cat Of Australia class hand out.
Hope this helps.
Cheers,
Eddie B

[paul.walpole]

Thanks for that Eddie B and previously Bob. That answers my question perfectly.
The converter is in and has been run but I have no drive with the new trans, Chasing pressures at the moment. Suspect the converter bi-pass / relief or trans pump although the trans pump was new 50hrs ago.
I bought a rebuild exchange trans from a company in OZ called EMECO. I did everything right, new scavange pump, new trans pump, cleaned out the system and it blew up after only 47.5hrs. Took it back, 1500km to the workshop it was rebuilt and they didn't put a retainer on one of the carrier gears. They said it would be a few days waiting on parts. The next day I got a call and they refunded my money and gave my original trans back saying it was going to be too expensive to rebuild. This is unheard of before and frankly I was shocked.
Another company build one up for me and as I mentioned, I still have an issue. One thing though that might point to the area. Just prior to the trans failure, my operator said when he pulled on a steering clutch the other track dropped out momontarily. I am guessing that oil pressure to the priority valve was dropped causing the trans to disenguage.
Any thoughts on this would be appreciative.

[Old Magnet]

Wow, one problem at a time
First I looked through my stuff and don't have manuals on D8K but do have on D8H so I'll post a couple that may be good for conversation.

I can understand the small amount of movement to build thrust on the taper roller bearing but the axial movement on the shaft sure doesn't seem right. Looks to be like everything should lock down tight to control the converter clearances. I'm definitely not expert here so hopefully Bob and edb can sort this out.

I also see that the D8K 77V received a new torque converter at serial # 5954-up so it would be good to know the number for this tractor.

[bob]

Paul, is the drive shaft turning or stopped when you put it in gear?
Later Bob

[edb]

Hi Paul,
what a trail of disaster!
The priority valve sends oil to the steering and brake circuits for safety reasons in that one must be able to control the machine before it can be driven, so your observation is correct.
If you have failing bevel gear shaft bearings this will cause the seal rings and their carriers to wear and fail causing the leakage taking all the trans pump output oil flow, thereby causing the priority valve to come into action.
You could, with all the associated precautions, block flow to the steering valve and see if the trans will function.
It is also not unknown for new trans pumps to fail due to a wear step within the hollow drive gear splines to contact the end of the new pump shaft and cause excessive end thrust loads on the pump gear inside the pump, this causes adhesive wear (galling) to occur on the pump gear and pump end cover faces--failed pump-- we always primed the pumps-old or new- with moly-lube before start up to give them a chance.
For a new pump it was reccommended to grind about 2 mm off the end of the shaft including restoring the taper-champher-. There was a Serv. Mag. article on this but I cannot find my copy just now.
Good Luck getting to the bottom of this current dilemma.
Cheers,
Eddie B.

[bob]

That spline wear is most common on 977's and 55's Eddy. Destroys a new pump in a day. I think Paul should look around the shop for a sungear or set of planitaries that might have been left out of the torque divider. Wouldn't be the first time that has happened.
Later Bob

[edb]

Hi bob,
indeed, any splined coupling is a candidate for this type of problem.
YES, now you mention it I have heard of the sun gears being omited, for some reason it does not put much load on the engine in this condition!!!!
Bob, your earlier question as to the drive shaft rotation will be a hint to answer this for us. Good question that!
Cheers,
Eddie B.