Installing New Gears:

[DK] I just finished installing 3.55 gears, six bearing, and four races. What a job! But satisfying. Here’s my story if you are considering doing your own gears.

This was the first time I’ve opened up an axle for a rebuild. Disassembly went fast; pull a locking bolt, and the c clips and locker gears with their fiction plates slide out, so do the two axels. The bearing caps come off and the heavy ring, attached to the carrier (kind of a hollow ball that houses the locker) lifts out of the axel. The pinion gear, which turns the ring, slides out after the outside nut is removed. So far, so good, I was cruising.

Speed bump #1. There are large bearings pressed onto each end of the carrier. (I had decided to replace them, although its not necessary for the gear change.) There was no way in hell that I could pull the bearings off the carrier. There is zero clearance between the bearings and the carrier so I could not use my bearing puller, and those babies are on tight!!. SO I took my dremel with a cut off wheel and cut off the thin roller retainer, and then cut a channel in the race almost through to the carrier and wacked the race with a chisel. That cracked the race and I could then pull it off the carrier.

Speed bump #2 There is a large bearing pressed fit onto the pinion. Well I’m replacing the pinion, but there is a shim under the pinion bearing that, per the instructions, I will need on the new pinion. Same problem, same solution.

Big bump #3 The ring is attached to the carrier with eight bolts. No problem. But the dam ring is also press fit onto the carrier! No way in hell could I get it separated from the carrirer. I tried heating it, I whacked on it, I even tried a small bottle jack rigged up between the carrier and the top of a door frame. All I did was crack the door frame. Harbor Freight tools to the rescue. I bought a 12 ton shop press for $75, free shipping (3 week delivery). I figured I could also use it to press on the new bearings. It worked great. All I needed to do was make up a few blocks out of oak to support the ring and oak press blocks on inside of the carrier so I wouldn’t crack the carrier. I pressed the old ring off, and pressed the new one on. Ditto pressing the new bearings.

Minor bump #4 Two worn pinion races are buried inside the axel housing. I cut two disks from oak and used them to back up the exposed edge of the races and pressed them out, and pressed in the new races. For the outer wheel bearings, I used a long coat closet pole running all the way through the axel, oak disks behind the bearings, and a heavy hammer. FYI, to my surprise, 8.8 axels do not have wheel bearing races. The roller bearings ride right on the axel shafts, and mine show some checking after 68K donor miles. I hammered in new wheel bearings using the old ones and a wooden block. Cruising again.

Major bump #5 Pinion clearance to the ring is set with two sets of shims. One shim ring goes on the pinion shaft and the pinion bearing slides down on top of the shim. The problem is that the pinion bearing is press fit and you can use any combination of shims from .010 to .021 to set the pinion depth. Once you press the bearing on, its back to bump # 2 if your wrong. The solution, per the instructions in the ring kit, is to grind or hone out the old pinion bearing (now utterly destroyed) making it easily removable, and experiment with shim combos until the depth is correct. A professional shop uses (I assume) a special tool to measure the pinion depth from the axel center line and select the correct shim size before pressing on the bearing. So, for $16, I bought a second pinion bearing, honed it out with a brake cylinder hone, and used that as my throwaway test bearing.

Fun step #6 There are also shims behind each carrier bearing, but they go between the bearing race and the axel housing and are combined to set the ring backlash. That’s the play between the ring and the pinion, and it’s the ‘klunk, klunk’ you hear if you jack up the rear wheel and rotate back and forth a little. I used a $15 dollar dial meter from Harbor Freight to measure the backlash. My ring and pinion is made by Precision Gear and it came with two shim holders. They replace the thick Ford carrier shims and hold and protect wafer thin extra shims used to fine tune the backlash and the tooth pattern. Tooth pattern is seen by using a white paste on the ring teeth. The pinion teeth leave a pattern on the sides of the ring teeth, and the pattern can be shifted on the surface of the teeth via different carrier and pinion shim combinations until it’s just right.

I inspected the Trac-Loc’s six friction disks and six steel plates. Three of six friction plates were all but worn through, although I didn’t notice a problem with the Cobra this fall, so I replaced the lot for $76. (My donor had an alleged 68K miles)

Monster step #7: This spring when I hit the gas!

All-in-all I would do it again. It was challenging, fun, and I saved save a few hundred bucks. (towards a stroker kit).

Kapitan
FFR 1258

Question: Why not 4.56 Gears?

[JG] "It has been sooooo long since I've fooled around with cars so, please forgive if this question/observation seems goofy. Seems to me that, with a 5-speed overdrive transmission, a 4.11 or 4.56 rear end would be a very reasonable daily driver / kick-donkey weekend (drag) racer. Yet, I've not seen many with that set-up. Any experience or opinions?"

Comments:

[JR] "You have answered your own question, if nobody (relatively) else is doing it......The only people I hear of running stump puller gears are drag freaks (exclusively), i.e., Anderson ford motorsports in Ill."

[RG] "The T-5 transmissions have a 3.35:1 first gear. With 4.11's or 4.56's you'd be shifting to 2nd gear at 20mph, and the power would come on so quickly that you'd just sit there and spin the tires, especially in a car as light as a FFR. Ford Motorsports sells a T-5 with a 2.95:1 first gear, but the 4.11's or 4:56's would be too much in this case also, IMHO. Seems like most FFR guys are going with 3.27's, 3.55's, or 3.73's if they upgrade from the stock 3.08's or 2.73's from the donor car. You don't need a lot of gear to get such a light car off of the line. I have 3.50's in my '66 Mustang with a T-5 (3.35:1 first gear), and 2nd gear comes quickly."

[CP] "there's nothing like driving a hi hp motor with a low rearend and traction. Greg Lapoint is running a 4.11, and I am running a 3.89. There were 150 cars at road America this summer and there was not a car ,cobra or otherwise that could stay with Greg or I on the straights at 150mph+."

[LS] "I have 4.11 gears in mine I run a powerdyne sc with 9lbs of boost, I ran it last summer at the track 11.96 with not being able to stand on it 1st or 2nd too much wheel hop, also I took it to Woodward Cruise about 400 miles one way ran down the hiway 80/85 mph just fine."

[D55] "

So, do what you'd like, and your idea sounds fine!"

[JM] "have also considered experimenting with 4:10's from my current 3:73's. There was a massive difference from 3:27 to 3:73! I figure 4;10's may give just a bit more snap in 2-3-4. It's easier than pulling heads. I have a 2.95 first gear T5Z. I was figuring the calculations would be around the same in first at a 2.95 ratio and 4:10's as it would for guys running the 3:34 ratio and 3:73's.
Fifth gear ? I am @ 2200 rpm @ 65mph. I guess 4:10's would get me up to around 2400? So I agree that 4.10's may not be too radical. Some guys have higher gears but are running 500+ HP!"

[DW] "The ZF 5DS-25-2 transaxle as used in Pantera's and ERA's GT 40 has a 4.22 rear. First gear is a 2.23 and 5th is .705. This gearing is good for about a 150-160 mph top speed with stock diameter tires and conservative revs"

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