VCCA Home Forums TECHNICAL - 1945 AND EARLIER 1929-1932 Noisy 4 speed gearbox

Third gear on my newly restored 1930 1.5 ton truck is very noisy and I'm not sure about the best way to proceed. I disassembled the gearbox and inspected the parts during the re-build but probably didn't check the slop of the gear on the shaft, not really knowing what to look for. The teeth were OK and I polished up the rough edges. Any thoughts on the cause and repair? Where to find parts?

What weight oil are you using in your transmission?

Did you install new bearings during the rebuild?

I did not install new bearings and the oil is the recommended 600 wt

The 600w originally called for changes over to a modern straight mineral oil(non EP type)of 140 grade which is sold by a lot of vendors in the states.
As for the noisy 4spd gearbox,I had the same problem with my '28 4spd.The main culprit was the mainshaft to clutch input shaft caged roller Hyatt bearing,and the breaking up of the case hardening on both the mainshaft spigot & the bore of the clutch input shaft,as the rollers use these surface as the inner & outer races.
I ground out the input shaft bore and ground down the the mainshaft spigot,and made a "floating" bronze bush with counter rotating oiling grooves in the bore and on the outside diameter to ensure proper lubrication.
I also found that the countershaft with low gear(machined in one unit)had badly worn roller race diameters.As the roller bearings are known as a "full compliment"type bearing,ie;no inner race,as the rollers run directly on the counter shaft itself.These being badly worn & pitted after 80 odd years of use,I fixed it this way:machined down the original "inner race ways" to take a modern NU style roller bearing which has a separate inner race and exactly the same bearing outdide diameter as the original New Departure C-1305 & C-1306 roller bearings.
After fitting all new bearings and bushes,re-installing and using the correct oil,no more horrible noises any more,other than the gears when they're in mesh and being used.Did this 25 years ago and it's never let me down,even carrying loads up to 2 1/2 tons.
Hope this gives you some ideas on a fix for your gearbox.

When rebuilding a transmission new bearings should always be installed to avoid unwanted noises from the old used bearings.

There is no need to replace the expensive bearings if they are in good shape. If defective, sure, then replace them.

Thank you all for your reply's. I should have studied it more closely when I had it apart the first time. In the meantime I have an overheating issue to work out. The engine is running great with new pistons, and rebored cylinders to match, but they may be a little tight yet. In this hot humid weather the gauge gets up to 190 plus degrees and boils over when I shut it off. I am temporarily using a modern gauge for more accuracy. I have tried all of the usual fixes except a new radiator. That may be next.

Used transmission bearings can appear to be in good condition when removed from the transmission for inspection. However, that doesn't necessarily mean that the old, used bearings are actually up to standards under load (been there and done that). Even though the bearings appear to be in good condition, they could still make an unwanted bearing noise when driving the vehicle. It is a matter of choice, however, since it is a lot of work to remove and reinstall the transmission, it is wise to replace the used bearings (along with the needed bushings) if you are doing a quality rebuild of the transmission. Otherwise, you may end up with unwanted noises in your transmission case requiring that the transmission be removed once again.

On the overheating problem, as a start you might want to get a flow test on your radiator to get an idea on how it is performing.