Hi Eddie,
I have been asked about some info on the 15A three stage torque converter. Apparently there may have been a service bulletin regarding changing the torque converter bearings from ball to roller type and a method for doing away with the freewheeling function. I have no such information in My Cat Library and there is no mention of these changes in my Twin Disc Model CO Service Manual that covers the actual manufacturer of these torque converters for that period of time. Do you have any such info or recollection?

Hi OM,
this Product Bulletin -- June 28 1961 -- is all I can find on this subject.
I do recall doing this once and seeing/working on several that had had the Free Wheeling Clutches removed.

My Master Index for Flywheel Clutches and Torque Converters only goes up to 1971 but should show any bearing changes in the 3 Stage units and beyond their production cycle.

Product Bulletin May 8 1962, tells of Hardened Steel thrust bearings to be used in place of earlier Copper ones.

The scans below, albeit for D8H, I believe would also apply to the earlier pre-D8H machines with 3 Stage Fuel Converters--


SORRY if the following waffle confuses things for you but I am simply trying to explain what I recall about the Ball versus Roller bearing usage in the larger early tractor T/C's.

The single stage units were announced in around 1966 for the D8H Powershift units at least from 46A 3044--up.
In my experience I believe the change from Ball bearings to Roller bearings would be for the later Single Stage units, BUT, is likely the difference between the D8H unit as compared with a heavier D9G unit--I stand to be corrected.

There are certainly both types that I have worked on and it may also be that with subsequent HP increases to the D8H that they upgraded the D8H/K units to incorporate the heavier duty Roller type bearings to take the thrust of the Impeller.--Serial Number checks in Parts Books may show at what S.No's this may have occurred at--if at all.

My literature does not go late enough to cover any possible upgrade from ball to roller bearings in the 3 Stage Fuel Units as is what you specifically asked about--may have to check NPR for any possibility of a conversion being possible to an early Ball bearing supported unit.

As an aside at a Cat School on Powershift Transmissions in 1965 we were told that there was a huge safety factor of transmittable power thru the later single stage units--something like 30 times.
Many years later I was testing a D8K with a sticky rack that was opened way up by someone falling for the sticky rack coming up short on true maximum rack setting dimension.
I am sure that the T/C cavitated!!! when Cat Engineers were questioned on this they said "No Way that can happen"
--I was the one testing it and the engine Rpm's definitely rose along with a strange rumbling sound coming from the T/C--????


Keep asking if you need more data or if I have confused you with the extraneous waffle.

Cheers,
Eddie B.

Hi OM,
have kept on looking and found some of this had been covered previously on here.

Two scans refer to a higher capacity shaft bearing and may be what you were actually asking about.

Plus some other scans on Fuel Converters from the past for perusal.

Hope this helps.
Cheers,
Eddie B.

Thanks Eddie,
I will see that this info gets relayed to the fellow that is in search of answers.

Thanks Eddie and OM you have cleared something up for me that I have often wondered about and that is how we could roll start our 15A D8's. Now I know. "The freewheel assembly is necessary only if it is desired to push-start the tractor"

Hi Phil and OM,
the Freewheeling Clutch was mainly to provide engine braking going down hill for Direct drive Tractors---push starts were an added bonus too --- and some engine braking only but to a lesser degree for T/Converter Drive machines--if my memory is correct from School back in 1965.
Cheers,
Eddie B.

Interesting bit while perusing my Twin Disc Service Manual.
I always wondered about Cat's decision to dump seal leakage to the ground.
Well, if you had the full as designed TD Torque converter/clutch package it included lines to drain the seals to a sump/tank with lift pump and filter that returned the leakage to the operating system.

Hi OM,
now that is very interesting to hear, I have always wondered too, now thinking on it some it could now be a suggestion for future excessive drain issues owners encounter as the T/C refrigeration type seals seem to be non-existent now.
It makes more sense to do this, but at extra cost. It will keep these jiggers going and be environmentally friendly to boot.

Are there any diagrams relating to the recovery system or only the description?

As an aside I feel sure Allis Chalmers used the 3 stage fuel converters in some of their range of machines also.
Have hazy recollection of a book stashed under the house on the operation of them--must dig it out over the weekend--thanks for the mind jab.
I wonder if they drained to ground also.

Thanks again.
Cheers,
Eddie B.

Yes, picture and diagram and a couple of pages of description which is pretty self explanetary:

More info: The charge pump or fluid pump maintains a 20 -60 psi pressure and functions to keep the converter circuit charged, so cavitation cannot occur. So your observation of cavitation under high load/speed test without this pump means cavitation can occur.