So working on rebuilding the steering gearbox that was on my 28 truck. The first two pictures are of a 27 gearbox I got from a fellow member. The next 5 pictures are of the one that was on my truck. Note in those pictures the way the gear was held on the pitman arm shaft. There is a groove in the gear that a thrust bearing fit in. It had the shown bearing on with the thrust washer over that and then the nut. The nut was just scrubbing against the cover which had 2 thick and 2 thin gaskets under it. So my questions are this; 1) Is that even the correct steering gearbox? It sure seems like it is original to this truck. The bolts that held the clamp on the frame had enough rust on them that there were no corners left on heads, or nuts. It was fun to take apart. 2) Is the way the gear is held on and the shaft endplay adjustment correct?
It makes zero sense to me why there would be a thrust bearing on the gear face as there is no rotation taking place there. The gear needs to be tight on the shaft as both the shaft and gear have a taper so as you tighten things down the gear gets tight on the shaft taper. There will be no rotation in the bearing as you steer and the shaft rotates. Also, it makes no sense when in comparison I look at the design of what is suppose to be the 27 gearbox I got from fellow member. That gear is held on by just a washer and nut tightening it to the taper. Then there is the collar as pictured that rests against the gear held in center by the nut. The two faces of this collar have oil grooves of sorts in them to keep lube flowing between the surfaces. Another note on this gearbox is it looks exactly like the one pictured in the 1925 chevy repair manual for the Superior series model K. It has the same cover style and worm adjuster plug style.
The gear box I took off my 28 truck resembles the one pictured in the last attachment which says it's from the 1930 Chevy owners manual, and the worm adjuster plug style is the same and the description for adjusting and locking that plug in place are described correctly for the style. That nut just scrubbing against the cover wearing a groove in it does not seem correct for adjusting the shaft end play.
I do have a Parts master price list catalog here effective Feb 1 1928 that has some pretty good pictures in it. All descriptions start out by saying "Sup" and then have a letter(s) (U,C,N, or maybe none) then the description of the part then what series it fits. Some descriptions have LM or LO but most have a single letter. I can identify the gearboxes and parts I have for the most part. Nothing that I can see shows that thrust bearing to hold the gear on. If a truck is considered a model 'K' ??? Then the gearbox in the first two photos looks like what should potentially be on the truck. I think either gearbox may work just fine on the truck. The one given to me has a smaller gear in it at 14tooth I believe to the other one being 19tooth. (side note, I'm thinking from various clues that my truck is a 28 LO)
Sorry for the lengthy post and hopefully it's not too confusing. Thanks, David
Hi David. It's been a while since I had my 28 box apart, but I recall it being configured like the second picture. As you have probably read in the manual, zeroing the axial clearance of the Pitman shaft is accomplished by adding or subtracting gaskets to/from the cover. By the looks of your box, my impression is somebody in the past was missing the collar in the second picture. They substituted whatever was on hand to make up the space normally occupied by the collar. Perhaps there was a handy thrust bearing and washer lying around at the time.
Hello David, do the engine controls for your 4 cylinder truck strap to the outside of the column like the earlier models, or run down through the center like the '27, and '28 cars? The service manual picture you show of the steering assembly is from a later year. The '28 and earlier models for trucks and cars did not have the allemite fittings on the tie rods and drag link as described until the '29 model year. At least that is the way it is in the US. It was part of the big unveiling and sales tactics for the "new and improved" six cylinder models. I think the steering boxes were manufactured the same, or very similar, except for how the engine controls were handled. If that picture depicts how the steering box you have is assembled...
According to my Parts List book for Capitol LM and LO trucks, they both used the same steering gear case part no. 345139 which uses the smaller gear (14 teeth)
Thanks for all the looking. BB my controls are external not down the center of the column. So the gearbox I got from fellow member must be the correct one for the trucks as it has the 14 tooth sprocket in it. I ended up rebuilding the gearbox that was in the truck with the 19 tooth sprocket because the gears show less wear than the 14. It came out pretty good. I don't have a super tight mesh but the free play is quite minimal. Gearbox not in paint yet so I suppose I could always do something different if idea presents itself. I guess I'll be turning the steering wheel a few more times to complete a turn with the lower ratio otherwise. David
