VCCA Home Forums TECHNICAL - 1945 AND EARLIER 1912-1928 Transmission detention springs

My truck likes to pop out of 4th gear and I’m guessing weak detent springs may be the culprit, anyone have any experience with this or have a source for springs?

Otherwise the transmission runs and shifts well, I replaced all of the ball, roller and needle bearings in it but left the bronze plain bearings because they were still pretty tight. I also replaced the input shaft with one from a 1931 which required a little modification.

-Tyler

I would try McMaster-Carr. They have many springs.

I have the same problem with my 28 car jumping out of 2nd gear box is fully rebuilt and I even rebuilt the ball joint of the gear stick to eliminate the slop. I get the feeling it’s the gateway isn’t quiet right and it’s not seating fully when engaged in the gear. Maybe check that when your in Top the slider gear is fully forward so the ball that holds the position has locked into its indent . Have I made my self clear ? Ray

You may want to check the teeth on the inside of the top & 3rd gear to see if they're badly worn,as well as the teeth in the clutch input shaft.You should also check the 3 rails that the 1st & 2nd,reverse and 3rd & top gear shift forks slide on for grooves,and especially wear,where the spring loaded detent ball drops into the hole in the shaft.Also check the faces of the 3 shift forks that slip into the shifting grooves on the gears.If the faces are worn,the gears won't get pushed into mesh far enough.It could also be a combination of all these things,as well as the the rounded knob on the end of the gear stick that drops into the shift gate.

I finally got around to this and I don't think it has anything to do with the detent springs or gear wear. It turns out that when the transmission is in high gear, the fork is actually past the detention slot ~0.3". When the transmission would "pop out of gear" the fork actually slid into what should be the high gear detent position. Thinking I must be wrong, I played around with it trying to verify whether or not this was true. Turns out when the fork was in the "high gear detent position" the gear was not in mesh, if you pushed the truck forward the shifter would move slightly as the high gear dog teeth would just barely contact each other. If I pull the gearshift a little further pushing the fork past detent position, the gear would mesh and I can't push the truck.

I'm scratching my head as to how this is the case, I'm guessing that there may be some parts and pieces salvaged from other cars/trucks that were used that weren't suppose to be used in this transmission?

At any rate, it looks like the fix is to make a new detent rail and move the high gear position forward ~0.3". I'll try to post some photos tomorrow if I get a chance, if anybody has thoughts or experience, I'd be interested to hear it.

-Tyler

I've got a 4spd gearbox top I can pull apart and check the shift fork rails if you're interested.It's a possibility that the 3rd & top speed shift rail may have been swapped with one of the other shift rails,or the 3rd & top shift rail is out of the 4spd gearbox that was offered as an optional extra for the early 1928 Capitol LO series trucks.The '28 LP & '29 LQ 4spd gearboxes are identical,except for the length of the clutch input shaft.The LO series 4spd gearbox will fit into an LP truck,but none of its parts are interchangeable with the LP/LQ 4spd.

Hi Kevin,

If you get a chance, I would be curious to see how it compares to the photo below:



The rail on the left is the one in question, as you can see, the neutral and high gear positions are really close together and you can also see the wear that has occurred as the fork pushed past that position to actually engage the dog teeth.

Below is a pic f the sliding gear dog teeth, which to my eye look pretty good, a little wear but nothing that should cause problems:



Lastly below is a picture of the input shaft which was NOS and only has ~2,000 miles on it:

I figured I would share an update on this. I ended up having a new detent shaft made, moving the high gear slot 0.275" After getting this installed, it works beautifully. Below are the two detent shafts, "old" on the left, "new" on the right:




-Tyler

Nice looking work.

Mike