Hey guys,
I got another question for ya. I had new 4.10 Precision Gears gearing installed 1 week ago. I notice two things which seem awkward to me. The first is above 60MPH, my speedo is not stable. It is jumpy. It that normal after changing gears? The next thing is when above 40MPH, when I let off the gas, I hear a rumbling sound and kind feel the vibration from it. What can that be. Hope you guys can help (you probably will).

Thanks

 

Who did the Install? And, Just cureous, did these happen before the changing of the gears?

For the Speedo question: on gearing changes in the diffs the speedo and milage will change a little. Depending on tire size and what size gears are put in. It seems like all you might need to do is swap the little plastic gear at the end of speedo cable that plugs into your transfer case. I know in my case when I went from stock gears to 4.10 gears and 33" tires the milage and speedo didn't change much at all. But when I went from 4.10 gears to 4.56 gears, there was somwhere between 5 to 10 mph difference in what my speedo sayed and what my accual mph were. Also, it could mean that the speedo cable is bad and may need to be replaced or it my be something with the gauge itself.

I'm not sure about the rumbling or the vibration.

 

His '94 Bronco doesn't have a speedo cable. The speedo is electronic and reads from a sensor in the rear axle. A gear change doesn't effect the speedo accuracy in this system.

Sounds like there may be a problem with the gear installation. Your speedo should not be jumpy after the change. Could be a bad tone ring on the ring gear, or not properly installed. As for the rumbling/vibration, could be gears improperly set up or some other problem in the axle or driveline. I would take it back to the shop, explain what it's doing and have them go for a test drive with you.

After my gear change, I noticed a vibration that I hadn't felt before, at least not that pronounced. When I checked it out, I found that there was no problem with the work that was done, the axle was fine, the problem was the driveshaft was out of balance and I hadn't noticed it before because it was spinning alot slower then and the vibration was very slight. I had wrongly attributed it to the tires. Driveline problems usually become more apparent as driveline speed increases and the new low gears set the driveshaft to spinning alot faster. I had the shaft re-tubed (it was dented) and all new joints in it, balanced, and no more vibration . Hopefully your truck's problem will be an easy fix like mine was.

 

I had the gears installed at 4 Wheel Parts in Oakland, CA. I dont think the rumbling noise is from the drive shaft. The drive shaft was reconditions 1.5 years ago. The sound kinda sounds if something was loose with movement while spinning.

 

Tone ring was already mentioned, but it could also be the speed sensor. Definately get it checked out.

 

well going to 4wheel parts was your first mistake. they are a bunch of ***** down there. but i would start with your driveline , it may need new ujoints. most ujoints only last a year or two at most and thats with normal hwy use. Did you also follow the break in procedure for your new gears? this to is very important. but if they never told you to do this then any thing wrong with the rear end is there problem and i would definatly take it in because if you dont catch it soon enough it will destroy your rear end axles an so on.