want go from 2.73 to 3.73 i ordered the gears and installation kit.
one local speed shop told me he wouldnt want to do a swap like that he said the 10 bolt rears howl with gears like that even when a pro installs them. also i know it will throw my speedo off, but by how much and can the trans (89 700r4) be recalibrated. can i change the plastic gear on the speed sensor in the trans.

 

Yes you can change the tranny gear.
Most aftermarket gears esp. Richmonds tend to howl.

I don't know much on 10bolts (I have a 9) but would you need a higher carrier?

 

I have 3.73 gears (from the factory) in my 10-bolt... they don't howl at all.

You will need a different carrier though.

 

The gears howling is purely a matter of what type of gears and how well they are set up.

Richmond Gear and the like will howl, how much just depends on how close the mechanic gets it to the sweet spot. If your mechanic thinks this is just a 10-bolt thing then he is mistaken.

It is possible to put 3.73 gears on a 2.73 carrier, you just need a thicker ring gear designed to make up the difference in the carriers.

I have had good luck with Motive gears not making noise. It is something of a trade off. Are you pushing the 10-bolt to the limit? Are you running a manual transmission? If you are running an automatic transmission with less than about 425 ft-lbs of torque I would try to stick to a less performance oriented gear set. That will give you a quiet ride with the rear end ratio you are looking for. If you are running a manual transmission or more torque then you probably need to maximize gear strength and tolerate the noise.

You can recalibrate the speedometer by changing the gears, but I don't see you making up the difference in just the sensor gear. There is a second gear on the output shaft that I believe you will have to change as well.