Don't know if you did, but now warmer weather you can go to #140 gear oil will help.
Ya have to be a trucker to drive these, as well as even a late class 8, you have to
'rake' those gears too. My wife drives a crunch box just fine !!!

 

I may be mistaken, but don't you have/need to double clutch?
Press clutch in, hit neutral. Release clutch. Press clutch in, press the gas a little (to try to match the motor to the tranny speed), hit first. Release the clutch, let er go!
I think that's correct!

 

Double-clutching works fine once you're moving, but at a standstill, nothing you can do to make the mainshaft gear speed match the input shaft speed (600 RPM). Mainshaft gear speed is 0 RPM at a standstill. Clutch drag is the most common cause of slashing at a standstill.

 

Don't these trucks have a clutch break?

 

If you are at a light and you shift into first from neutral and stopped, let the brake go and "roll" into first, let the truck roll help you pull into first with clutch depressed, then work clutch and gas to let her rip without grind. It's how I do it. And when shifting from third to second (downshift) don't doodle around, do it quick, to avoid grind. I also put in 140 weight and it helped a ton, especially on initial warmup.

Jonathan

 

These crash box transmissions have no synchronizers, at all. Not sure what a clutch break is. These clutches are pretty hard to break. Common practice, to use the clutch when downshifting so the engine acts as a brake. This normally only in heavily loaded trucks decending steep grades. Clutches do wear out, especially if run out of adjustment and or driven by a driver who slips the clutch a lot.
Hope I said that right, have not had my coffee yet.

 

All this is why I enjoy driving my 'modern' 1954 model!

Can't you keep your the clutch pedal depressed? Most red lights last only 30 seconds or so.

 

No they don't. Clutch Brakes are typically on larger Class 7/8 trucks.

Sitting at a stop light is the perfect example of the usage of a Clutch Brake. The Clutch Brake simply slows and stops the transmission internals from spinning so that you can shift into gear without grinding. Push the clutch in 3/4 of the way and it works like a "normal" manual transmission, push the clutch all the way to the floor and the clutch brake engages slowing the transmission internals.

Good video with an explanation.

 

Sounds like you clutch is not fully engaging and needs adjustment. Also make sure that you are not using multi-vis or light weight gear oil in the trans. You need the resistance in the trans to stop the gears faster when the clutch is engaged.

 

I am not sure what was in the transmission but all I could find at the local store was Valvoline 85w140. They did not have any straight 140w that I could find. I did notice a slight improvement in the problem. I also adjusted the clutch out about 3 turns and that helped a bit as well.

 

Sadly this is in-town Atlanta so there are some lights at big intersection that can last between a minute and a half and two minutes. While I can hold the clutch that I was always taught I was wearing it out by doing this. I think this truck might be more at home on county roads in rural GA.

 

If I can find it does it matter whether it is GL-4, GL-5 conventional or synthetic?

 

I have to say this is the first time I've ever heard of wearing anything out by holding the clutch pedal in.

Can you tell me what part is getting worn with the pedal depressed?

 

The throw-out bearing

 

Get the 140 weight at o'reilys, they have it, I think it's gl4.