The Stovebolt Site Forums The Shop Area Driveline Replacing gears

I'm replacing the gears in a 1950 1/2 ton. I bought the 3:55 gears and instalation kit . The instructions say to check the ring gear run out by running a dial on the back off the ring. The spec is +-.002. That would be a total of .004 high to low. I find I have .005 high to low. I took the ring gear off and checked the carrier run out and found it has about .0015 run out (passable tolerance). I Cleaned everything up again put it back together and run out remains the same .005 high to low. The lash runs from .007 to .014. I spoke to the guy I bought the gears from and he says he never heard of such a problem. He said it would probably be alright but if there is a problem he would warranty them. Some people are telling me I'm going too crazy trying to be too precise and these trucks weren't all that precisely built in the first place. I had to wait 2 months for these gears and I'm almost afraid the gears they replace them with won't be any better. The other problem is I probably have 6 to 9 months of work left before I will be able to drive this thing. So should I try to run them and see what happens or should I bite the bullit and send them back now?

I suspect you have a high spot you are not seeing on the carrier face. Do you have access to another carrier?
If not you may try finding a machine shop that can true the carrier face.

Pill the ring gear off & make sure everything is clean or no burrs. Put the gear on 180 degrees from were it was. That might make it fall in specs.

I ran flat file on carrier surface. Flat file the ring gear. Rotate ring 180 degrees.same result. I might put the old 4.11 gears back in and see what happens. Obviously if the run out comes back into tolerance I have a bad set of gears.

It's taken a few weeks to get it done but I reinstalled the original 4 series gears just to make sure the carrier or bearings weren't the problem and found about .002 runout. This is within the acceptable tolerance. After going over all surfaces with a file and rotating the ring gear to a different position and reinstalling the new 3 series gears I still have .005 runout. The original gear set had 2 .0016 shims for a .0032 total on the pinion. I added .001 to bring the total pinion shims to .0042. The wear pattern is pretty centered and looks good. With the run out I have the best I could get was from .007 to .012 back lash. The vendor I bought the gear set from thinks I shouldn't have a problem. He said if there is a problem he will warranty them. I hope he's right.

Good luck, but starting out with a known problem that severe doesn't impress me. Is the vendor willing to cover labor costs and a new installation kit in the event a warranty is needed? Once a gearset fails, it would be foolish to install a new set of gears with worn bearings.
Jerry

I agree with Jerry. Please tell us you method to determine your run out to make sure the parts are just out of specification.

I put a dial indicator on the back of the ring gear and had .005 run out high to low. Then I checked the back lash and found it ran from .007 to .012. As I said when I spoke to the vendor he didn't think I would have a problem. I will call him again and ask if he has another set to exchange with. It took him almost 2 months to get the last set to me. I think he gets them from China. He seemed like a straight guy so I hope I don't have a problem.

By reinstalling the original ring gear and getting a good reading, you have pretty much eliminated every possibility except the new ring gear as the source of the runout. I'd be very reluctant to run the gears at all unless the vendor will agree to reimburse you for all the costs of reworking the job in case there's a problem. Most vendors are going to try to simply replace defective parts, with no compensation for labor or incidental expenses associated with replacing the parts. In the case of a ring and pinion change, the peripheral expenses can be pretty close to the cost of the defective parts.
Jerry

I wonder if the latest run of gears are all bad? I just put a set in last week and the run-out was at the max.

If I were planning on driving cross country towing a trailer at 70 mph I wouldn't even think of using gears with .005 run out. Im planning on driving down to the beach or up to the ice cream store once a week in this thing. My biggest fear. Ill spend money to ship the gears back, waist 2 more months and the gears they replace them with will be as bad as what I have.

This is just me, but I would run them, as long as they run quiet/no howl.

The variation in backlash would be my primary concern. It will create a rhythmic hum that will not improve with age. I listened to a Dana 60 in a 59 Burb do that all the way from California to Tennessee after installing a set of new 3.73 gears that had a backlash variation. When I parked it 10 years later, the noise was still there.
Jerry