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How hard to install gears?

1734 Views 12 Replies 6 Participants Last post by  KK95GT
I was wondering how difficult it was to install gears in the rear end of my mustang?...I'm very mechanically inclined and always do all my own work to my car, but never touched the ring and pinion in my life...I currently have the stock 2:73 and I want to upgrade to the 3:73...A shop will do it for me for a couple hundred bucks, and it is not the money that I am trying to save...The reason I want to do it is b/c
1) I want the knowledge and experience
2) I don't trust anyone to do anything better than me if I know how to do it

I figure since they are only charging 200 or so to do the install it can't be that bad or it would cost a whole lot more...The car is not an everyday driver so I can certainly take my time...Question is should an inexperienced guy do this, I mean there has to be a 1st time for everything right?...Also is there any tricky things to look out for etc.?...I really would like to do it myself but if you guys (please only respond if you've actually done it and know that it can be done safely if I'm careful) think I shouldn't then I guess I'm stuck turning my baby over to someone else...Also how many teeth do the 3:73's have, is this how I would correctly identify the gear set? I don't want to buy something off of ebay or something and it not be 3:73's...

Any detailed info on this is greatly appreciated!!!!
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I would leave changing the gears to the pro`s. It`s $200.00 well spent
Thanks for the opinion, have you done it before? What qualifies you to say that...Not being mean just asking for more info than your opinion statement...thanks
if you do not have a lift. its goin to be really really hard to get to the required torque of the pinion nut from underneath on the ground. it will also be fun trying to get the ring gear back on the carrier without the right stuff. dont forget checking backlash, and reading patterns. not to mention what to do if the wrong shims are installed.
Well I do have a lift in my garage so that is not a problem...Anyone think it might be a fine to give it a try?...Thanks
I can totally relate to what you're thinking. I have both a 66 Convertible and 95 GT (the 66 since '79) and other than the engine machining work and a trans rebuild, I've done everything else myself. If you want it done right, you do it yourself has always been my experience through the years.

The '66 has always been easy, 8 bolts to pull the axles and then swap the pumpkin out. Unfortunately the '95s 8.8 is the same cheap PITA design that GM etc uses - you're stuck working under the car.

I've had a set of 3.55 and 3.73 gears sitting in the garage for the '95 all summer. Can't make up my mind which to go with. They want $350.00 to $450.00 to install them around here so $200.00 sounds like a good deal for sure but what will you get in the end quality wise - that's the big what if.

I'm planning on doing them myself. I don't mean to knock on the service techs, but I don't think any of the local service guys around here that do gears had to get college degrees first. If you take your time, how hard can it really be? I think there's a lot of hype put out around gears. If I had listened to all the "you can't do that" stories, I never would have attempted the welding, bodywork, painting, suspension, engine,upholstery, etc work I needed to do. I have a whole shelf and wall full of 1st place trophies from over the last 20+ years and never once had any training on how to work on cars. If you're mechanically inclined, read a book (ie. do your research) and take your time and you can do anything!! And probably better than the guy rushing to get it done so he can get paid and move on to the next job.......!

Couple of notes:
1) Get Ford gears. I've been told by a couple of techs that Fords mfg specs are tight and 95% of the time you can just use the original pinion shim with no worries on the pinion depth. After that, get a dial indicator and base to set your backlash and you should be good. If you want to be more high tech about it, Summits last flyer had their p/n RAT-10006 pinion setting tool available for only $29.95.
2) If you have ABS you'll probably need new sensors. They're plastic and almost impossible to remove w/o breaking. (Another $120-150.00 to add to the project - partly why I've put off doing mine, the cost keeps escalating...)
3) The pinion takes like 140 ft/lb to crush the pinion collar. Make sure you have a big enough torque wrench.

Let us all know how it works out. Maybe it'll give me the incentive to get on the ball and get around to doing it this winter!
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3.55 Gears = 39 tooth ring, 11 tooth pinion

3.73 Gears = 41 tooth ring, 11 tooth pinion

Again, what many techs have told me, stick w/ Ford gears.

Also keep in mind your speedometer gears and what changes will be rerquired. The 3.55s will work with a 23 tooth driven gear in the trans and be accurate. The 23 tooth is the biggest driven gear you can get. For the speedo to be correct (this varies through the years but most of the time ) you will need to change your transmission speedometer drive gear for the speedo to be correct with 3.73 gears.

This means pulling the shifter out, dropping the H-pipe (hopefully no rusted bolts on the headers, oxygen sensors, or the air tube to the converters to break) and pulling the tailshaft off the trans in order to slip the $10.00 plastic gear on the output shaft of the trans!

Part of the reason I keep procrastinating and putting off deciding between the 3.55s and 3.73s and don't get around to making the gear swap...........
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i never tourque the pinion nut...what iv always bin told by my uncle who is a ford mechanic is to tightin it till you have 15-20 inch pounds of rolling resistance for used berings and 25-30 for new ones
The in/lbs idea makes sense.

Along that line, I've been looking at the "crush sleeve spacer kit" instead of using a crush collar. Has anyone ever used that instead of using the crush colllar? Seems like that would be easier to use/reuse in terms of adjustability if you do have to re-adjust the pinion depth and also wouldn't require the 140ft/lbs required to crush the non-reusable crush collar.

The in/lbs way of setting it up would definitely seem to make sense if you're using a fixed thickness sleeve spacer and shims to "tighten up" the pinion.
im running a pinion spacer now and from now on thats all ill use on my own rears...the in/lbs is the way to do it just make sure your checking the rolling resistance and youll need a very good tourque wrench
What year mustang do you have? If it's a T-5 you don't have to change out the drive gear on the main shaft. Just change the driven gear. On the driver side of the tranny there is a tube were your spedo cable plugs into. There is a 11mm bolt that holds it on. YOu pull that out and replace the little plastic gear on the end. If you have a yellow drive gear (7 tooth) then you will want to get a 21 tooth red spedo gear. ( Go to their webpage and it will give you list of years or trannys, gear ratio, and tooth ratio.
for around the same price as 50resto you can get the speedo gears at the dealer, and you never know they might even have them in stock so you dont have to wait.
94-98 5-Speeds and Automatics used 8 tooth drive gears.

96-98 Cobras used 7 tooth drive gears.

The biggest driven gear you can get is a 23 tooth. With a standard 8 tooth drive gear, the 23 tooth driven is only good up to 3.55:1 gears. After that (3.73 and above) you have to change the drive gear to a 7 tooth.

8 Tooth drive: 3.08=20 tooth, 3.27=21, 3.55=23
7 Tooth Drive: 3.08=18 tooth 3.27=19, 3.55=20, 3.73=21, 4.10=23
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