Can a DIY-er Do His Own Gear Swap?

Discussion in '1996 - 2004 SN95 Mustang -General/Talk-' started by sneaky98gt, Mar 20, 2013.


  1. sneaky98gt

    sneaky98gt Mustang Master

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    Sure he can!

    After having my car for almost 7 years, 3 of which with a supercharger, I FINALLY swapped out the gears! The stock LSD was also starting to give some trouble locking up. So out go the 3.27s and in go the 3.73s.

    First thoughts: wow, what a difference! The lag from a dig with the stock converter is nearly gone. 2nd gear pulls onto a highway are much more fun. 3rd gear (1:1) pulls with the converter locked are freakin' awesome. And ironically, the first several tanks of gas I have gotten BETTER gas mileage. Albeit they are both entirely city driving, it went from around 15-16 average to over 18 on both of them. Best city mileage I've ever gotten.

    I also did the swap myself. I was a little worried at first, but it was actually really easy. The only special tools needed are a dial indicator/mount, a hydraulic press, and some way to get the bearing races out (I just used a brass punch and brute force). I had no real snags on the entire install. I was able to get backlash to .0135" (recommended is .012-.015), which is pretty much perfect. Teeth contact pattern looked perfect, too. So far, I've got nearly 1000 miles on them, and they are quieter than the stock gears. I used full synthetic Mobile 1 75w140 oil with one bottle of Ford friction modifier.

    I also went ahead and installed 31 spline axles at the same time. I shopped around for a while, and got great deals on all of the parts (all new). In the entire build (FRPP gears, Ford bearings/install kit, new 31 spline T-lok, new Superior 31 spline axles, Superior wheel studs, oil), I've got right at $600 in everything. Not bad at all for all new parts on a 31 spline upgrade.

    Also, big shout-out to Tousley Ford. If you ever need any FRPP parts, check them out. I got FRPP gears for $130 shipped, and the good install kit (GT500 bearings, better gasket, etc.) for $90. They've also got 31 spline differentials at a good price.

    New track times coming soon!
    #1
  2. usaf_branham

    usaf_branham Member

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    nice, im surprised you didnt go with 4.10's with the auto.
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  3. sneaky98gt

    sneaky98gt Mustang Master

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    If it was purely a street car, or purely a track car, I probably would have. After driving my granddad's Mach with 4.10s, they are definitely a lot of fun at [mostly] legal speed on the street, and would work nicely at the track with some 28" tires. But since I run at the track on a shorter, stock height tire, I had to go 3.73. 4.10s at 6200 rpm only get 115 mph; I'm trapping upper teens, so that'd mean I'm over 6000 rpm for at least a couple seconds, up to almost 6500, on a given run, and I didn't want to do that.

    3.73s get me 122 mph at 6000 rpm, so that's almost perfect. It will be perfect when I get done with the next few things on the car. :D
    #3
  4. Kornnut

    Kornnut Founding Member

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    Did you pull the rear from the car or do it while it was under it?
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  5. tank_567

    tank_567 Active Member

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    Very nice Will! Cant wait to see the track times:nice:
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  6. sneaky98gt

    sneaky98gt Mustang Master

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    Nah, did it all under the car. I jacked it up off the ground a good couple of feet. It wasn't that bad at all; I just about could sit up underneath it. The only aggravating thing to do under the car was beating the pinion bearing races in and out, and tightening the pinion nut. But even then, they weren't really that bad.

    As I mentioned earlier, the swap really was a lot easier than I thought it would be. If you have a lift, the right tools, and the know-how, this could easily be done in a few hours. A simple gear swap could probably be done in two. Shops definitely make a nice penny on doing these swaps for people.

    Me, too! I gotta go talk to Eric about fixing my shift points first.
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  7. 72 fastback

    72 fastback Member

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    I am glad it worked out for you. I would love 3.73s in my 02. I would have to lose the kenne bell tune and get a custom one I imagine. The car might actually launch pretty good wih the upr upper and lower control arms and torque box reinforments. I can't wait for your next video. :nice:
    #7
  8. usaf_branham

    usaf_branham Member

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    That is why I switched from 4.10's to 3.73's, I was going thru the traps bouncing off my 6k rev limiter.
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