The Stovebolt Site Forums The Shop Area Driveline What's normal drivetrain noise?

I recently got my '46 on the road. I've replaced all the u-joints and there is little, if any slop along the drive line to the rear end. I understand that the straight cut gears in the 4 spd are supposed to make a lot of noise but mine seems quite loud. In particular I've never used it on blacktop in 4th gear. While it's quieter than 2nd and 3rd, it still howls when under load at 35-40mph. My dad remembers these trucks being loud inside and if you watch the old WWII era videos of the Chevy trucks you can hear the gear whine. I thought I'd see if this is supposed to be common or I have some bad bearings in the transmission.

those trannies are always noisy, and considering the age [and likely abuse of a 1T hauling brick!] it certainly could be needing an overhaul, but make sure some of the sound isn't from the pinion bearing

Bill

They are noisy in all gears but high. There should be no transmission noise in high.
Noise on the pull in high is most likely pinion bearings.

This is the 3/4 ton I'm referring to. I had the rear open and everything looked nice and clean concerning the bearings. The noise seems to be at or under the seat. I can also feel vibrations through the steering wheel. I wouldn't think that pinion vibrations would resonate up to the front.

I did open up the short section of enclosed drive shaft behind the transmission. The U-joint there seemed pretty sloppy and wore out the brass sleeve. I put a new sleeve in but didn't mess with the u-joint since it's hard to find. Could this be the source? Maybe too tight? Also I filled this separate from the transmission with gear oil but this is still fed by the transmission oil too?

On a side note about the enclosed drive shaft, has anyone converted it to open using a modern center carrier bearing, custom shaft, and a 4spd transmission from a larger truck?

Can you update us on the noise problem in 4th gear? Your symptoms sound just like mine. More of a worn bearing sound in 4th gear. I wonder if the way the 4th is an internal gear that is pushed into the gear teeth on the input shaft makes a difference with how the input shaft rides in the bearings. In other words the power is straight through rather from coming from the gears on the counter shaft.

One more thing, my needle pilot bearing between the main shaft(output) and input shaft is new.

There is a link in my signature to a video as a reference to the sound of a 46, granted I have a 2 ton, its the same 4 speed transmission. There is plenty of gear whine in 1st through 3rd. 4th is pretty quiet. Any whine you can hear in the video with the 4 speed in 4th is the auxiliary transmission, it whines in both under-drive and overdrive. Next time I have a load and remember the camera, I'll capture what it sounds like working, no load in the video. The whine in 2nd and 3rd loaded to the weight rating and pulling a hill is like nothing else.

The whine however, does not induce vibration that can be felt anywhere in the truck. Sounds like that sloppy u-joint could be a contributing factor, but I'm not that familiar with the enclosed driveline trucks.

Some more info on the 4th gear noise.

I have a 1946 GMC 1.5 ton. Standard 4 speed, no power take off of any kind. U joints are new. Drive shaft is open type. Center propeller bearing is smooth, tight, and rubber propeller bearing cushion new.

I test drove the truck again to listen carefully. The sound always goes away when I depress the clutch pedal. This might be more of a higher RPM that creates this noise. Sometimes Under light load or no / little acceleration I can make the noise go away in 4th gear. This weekend I'll check the clutch throughout bearing in case it's spinning a higher RPM's. I'll also pull the top of the transmission case and look at the 4th gear again for wear. It looked fine the last time was working on my transmission. What should I be looking for with the gear spacers? Is there a tolerance spec?

My dual performance differential has a fair amount of gear lash in the pinion, almost a 1/16" but it runs good with no noise that from the rear of the truck.
Pilot bearing at the crank is new too.

mjl

Considering the backlash between the ring and pinion should be .008"-.010" on most, I think your .062" is giving you more noise than you think.
And yes, those small cab trucks really reverb any noise.

I agree with Dave, .062 is too much lash and those gear will sing like a church choir.

Thanks I'll start another topic on this as I highjacked this thread.

Update on 4th gear only noise. It was caused by a worn forward roller bearing on the counter shaft. I found a used transmission at the Iola car show in Wisconsin and it was about the same cost as bearings. Installed new trany and noise gone and truck now shifts with little grinding. Happy camper.