what are some of the common problems when you change the rearend gears on a 8.8 ford rear end?

 

rear ends are fairly easy. the biggest problem would be the parts store getting you the right parts

 

Always use Ford Racing gear sets. With aftermarket gear sets you will have to check and adjust pinion depth, backlash, side clearences, etc. Ford 8.8 rear ends are set up at the factory with master housing dimensions. The ford racing gear sets are machined with the same tolerances as the factory gears just measure the height of the pinion gear and compare it to the pinion gear that you took out and use the appropriate size shim and everything will line usually line up. My Ford racing pinion matched my old pinion exactly so i just reused the factory shim. You should always check all the measurements and run a pattern on the new gears to verify that everything is right, on my mustang i didn't need to make any adjustments and i had the job done in 45 minutes. I think summit has the gears for less that $200 dollars, the set comes with a crush collar and shims, all you need is a pinion bearing (like $20 at a parts store) and limited slip additive if you have a limited slip diff.

-Jon

 

I've never had a problem with Yukon Gear sets and my bud swears by Precision. I'd go with the best deal you can get for a quality gear.

If you're a '94 model as your user name appears to show, I'd get a quality rebuild kit while you're in there if you have some miles. Axle bearings with seals, maybe some carrier bearings, etc. It's a place you want to be once.

But setting up the rear is something you don't want to do twice, if you do not have the capacity being tools or the know-how there are many who can do this for you.

 

I have also used Yukon gears and they work great, but they usually require more time to setup that the Ford Racing gears.

-Jon

 

I was checking on the fordracing site today - http://www.fordracingparts.com/parts...rtKeyField=255

and saw they had a little disclaimer on the gears *Not legal for sale or use on pollution-controlled motor vehicles.

Any idea why this would be? I was looking at the M-4209-G410* 4.10:1
Is there a 4.10 they call street-legal

 

The higher ratio changes the RPM of the engine throughout the test driving cycle. That potentially affects emissions and would have to be tested in order to be certified. Ford could certify the gears ONLY if they tested them on every single application to which they could be fitted. That is clearly impossible, so they are not certified as smog legal. Will they cause your vehicle to fail a tailpipe test? Somewhere between no chance and highly unlikely. If you do not have to meet a CA-like part certification requirement, then go for it.

 

Where have you had an emission test where they checked your gearing?

Places here do the safety and emission... they could careless about anything else from stereo to paint, etc.

I've had the 4.10:1 gears for a long time, no problems. Going from a 3.55:1 to a 3.73:1 isn't enough difference to warrant the cost IMO. I'd go 4.10:1 or spend that money a good cam and some full length headers.