I was in the midst of changing gear ratios in the rear end last weekend and ran into an unexpected snag. It turns out that Ford changed the Pinion bearing for all 2013+ 8.8 rear ends. This was due to a trickle-down effect from the Shelby. in order to run the car at the advertised 200 mph, a better bearing was needed.
The bearing that I took off the pinion gear was a KOYO 4190 LFT, which is a 3.5" OD bearing. The pinion bearing I was expecting to see was the same one Ford has used for a long time now, which has a 3.25" OD. Obviously, for a project I thought was going to be done over the weekend got delayed with having to order this new bearing. Through Ford, this bearing is about $70, but I was able to order it directly from a KOYO distributor for $25. Now I will have to wait until this weekend to finish my project.

 

This started in 2011. I ran into the same issue with my 2011 GT. In fact ford lists a. Early 2011 pinion bearing and a late 2011 pinion bearing.

How did you determine proper pinion depth?

 

Pinion depth is pretty easy to deal with using Ford gears. I have done a ton of gear swaps to date, and 99% of the time as long as you use the same pinion shim as the factory set, it all re-assembles perfectly. It does help that I have a press in case I have to change the shim out after checking pattern though.

 

Here is a quick picture showing the difference. The new larger is on the left, the original is on the right. I got a set of new-take-out 3.55 gears that still had the"old" bearing.

 

What's your reason for switching to 3.55 from 3.73? It it for road course use?

EDIT: I just saw your other post on the 3.31 vs 3.73 thread. That answers my questions. I'm very interested to hear how 3.55s change your track experience. I'd be curious to do the swap myself.

 

Yes, this is mostly my reasoning behind making the change. I do about 6 - 7 track days a year, and with the tracks I visit I was finding myself having to upshift to 4th on some of shorter straights, or slower corners 2nd was too short, and 3rd not enough. I was riding in a friend's 2012 GT with 3.31 gears, and we both agreed that somewhere between what he had and the 3.73 in my car would be perfect. Not too mention I should see a little bit of an increase in highway mpg's. I will let you know what I think after my first track day of the year in May.

 

Where do you typically race?

 

Gingerman Raceway, Grattan Raceway, Waterford Hills, Mid-Ohio are our usual stops. Pretty much anything within a couple hours of SE Michigan.

 

Cool, I'm probably going to head out to the Gingerman and Grattan this year. I hear Waterford isn't as friendly for newbies, as far as run-off areas and not destroying your car if you go off...so I'll wait on that.

 

I would agree with that. What group are you looking to run with? I'm an instructor with 3Ballsracing.com and attend most off their events.

 

Not really sure. A buddy races a few times each year, and I'll try and go with him once or twice. I haven't looked into it too much yet, but I hear they offer classes/instructors which I'll probably do a couple times to get the hang of it.

 

Well if you come to one of our events, stop on over and introduce yourself. I'd be more than happy to show you around any of those tracks

 

Will do!

 

Jason, I'll probably see you at Grattan in July with 3Balls. I live about 10 minutes down 275 from Farmington Hills by Ford Road. Which group do you instruct typically? I think I'll be in the intermediate. I did Gingerman last year with BMW CCA in Novice since it was my first track day in my new Mustang, and my instructor recommended I go in the intermediate next time.

 

By the way. For now I decided to get around the 3.73 issues another way. I'm getting a designated set of wheels/tires for the track, and I'm going with 275/40-19. That's 0.6 inch larger diameter tire, and according to the gear ratio calculators I found that's equivalent to staying with the Brembo tires and having 3.64 gears. I should gain ~2 to 3 mph more in each gear.

 

You can sometimes get away with using the factory shim. Ideally you want to measure the thickness of the old shim and the height from the face of the pinion gear to the bearing landing on the back pinion gear being removed. Add these two together and this becomes your base thickness. You then want to measure the height of the new pinion gear from the face of the pinion gear to the bearing landing on the back of the pinion gear. The delta between (old shim + old pinion gear height as described) - new pinion gear height as described = new shim thickness. Using the old factory shim will work but you could end up with some humming.

I like setting pinion preload at about 26 inch pounds when using new pinion bearings and about 18-20 pounds if using old pin ions bearings.

Pinion depth should be right on at this point.

Then install your carrier and check the pattern. If you need to shim the carrier remember if you add some shim to one side you need to remove that exact amount from the other side.

You always set pinion depth first. Pinion depth is pinion depth. If pinion depth is right on and it will be with my method as described and your pattern is not correct then you need to shim the carrier. You never shim the pinion to compensate for a misaligned carrier.

 

See, I have just the opposite problem. I run with 275/35/18 slicks from rehagen racing. They are a shorter tire, and with the 3.73 gear it's the equivalent of running a 3.90 on the stock street tire. Going down to the 3.55 just brings me back to what I would see on street tires and the 3.73.
I will be there at Grattan, instructors are usually for groups 3 & 4 (novice to intermediate novice). I typically run with group 1 or 2. Passing rules are different there though. Group 2 is passing anywhere on track with a point, and group 1 is open passing anywhere. 3 & 4 are only on the straights. Look for me out there, all instructors wear shirts with obnoxious sayings on them.