Gear Change

[Drago]

I am looking to change my gears in my 91 gt and was just wondering what all is involved in doing so. Besides the gears do i need to buy anything else? Can you change the gears by just taking off the back cover of the differential? If anything else is important please let me know also.

 

[Dtowncats]

Don't know too much about this topic but if you are going to do this, while you are back there get a traction-lock rebuild kit for about $50.

 

[TIMMY2734]

http://www.corral.net/forums/showthread.php?s=&threadid=445210&highlight=gear+swap

 

[Idwitheld-1`]

I am looking to change my gears in my 91 gt and was just wondering what all is involved in doing so. Besides the gears do i need to buy anything else? Can you change the gears by just taking off the back cover of the differential? If anything else is important please let me know also.

...this was my experience. I am not an expert. I am probably missing many things....but here goes
You will need a speedometer gear to match your gear set.

I just did my gears 4 days ago. Most do the gears by popping the diff cover. I chose to removed the axle. Took an hour to drop the axle, but allowed me to have "comfortable", access. I don't have a lift and did not want to muscle the pinion nut under the car (done it before it it can be very tough).
It really helps to have air tools. That really makes it go faster.
Things that can be tough:
1. Removing the carrier bolt. If its the first time its been out it may resist you. Also, if the bolt looks chewed up replace it ($3.85 at dealership). Don't risk stripping the head and creating a future headache.

2. S-spring. I tapped it out with a punch and hammer. (don't forget to remove the carrier pin first)

3. C-clips. Use a "magnet on a stick" to remove them. You amy need to spin the clip with a small screwdriver...but it will come out.

4. Don't mix up the carrier shims. Keep them seperate and remember what side they belong to.

5. Pinion gear: I used a long taper punch to wedge the pinion flange to the pumpkin housing. Use the non-threaded holes for this (not the drive shaft holes). This is where the impact driver saves the day! Replace the pinion seal at this time.

I replaced my pinion bearing rather than using the original one (110K miles). Get the pinion shim off of the old pinion gear. Use a bearing splitter and hydraulic press (I have a 20 ton press). Use this pinion shim on the new pinion gear. Press bearing onto pinion gear. It can help to heat up the bearig (in your kitchen oven) and freeze the pinion gear. I have done this and slipped the pinion bearing all the way down to the gear face with no tools at all! Not all gear/bearing toleraces will necessarily allow for this...and if you need to re-shim then your back to the hydraulic press....
Don't forget to use a NEW crush sleeve during re-assembly. Crush the pinion flange / crush sleeve onto the new pinion gear. This can easily take 500 to 600 pounds of force. Do not over tighten the pinion bearing. You need to measure the pre-load on the bearing. 13-20 inch / pounds of drag is typical. Too little preload the gears will bang and the bearing will probably chew itself to bits. Too much and the bearing will overheat and chew itself to bits.

6. Carrier ring gear. The gear may require persuasion during removal from the carrier. chunk of 2x4 and 3lb sledge. Again use the shop press to assemble the new ring gear to the carrier (most use the bolts to pull the ring gear onto the carrier...) Use the bolts (all of them) to ensure alignment BEFORE pressing the ring gear completely on. I had to do this twice because one friggin bolt (of 10) would NOT align to the hole! Torque to spec I used red loc-tite on the ring bolts.
Now is the time to rebuild your trac-loc.(did that last summer).

7. Change carrier bearings here...(did that last summer) Not required. Change axel seals and bearings (did that last summer)
8. Insert carrier and shims. This can be tough because of the tight clearances and the bearing races are kinda angled going in...will require some gentle alignment (persuasion). Don't force it. Add caps, tighten cap bolts.

9. Measure gear backlash. 8-15 mils is the spec. I had 13.5 mils.
10. Measure gear mesh. Need centered pattern. It helps to see pictures of this...I used an issue of MMFF with pics of good and bad mesh. Adjust carrier shims and/or pinion shims accordingly. I used motorsport gears and probably was lucky with a centered mesh and 13.5 mils of back lash.

11. Align axel, upper control arms, insert springs, lower ctrl arms, shocks, quad shocks, brake fitting, e-brake cable, fluids, friction modifier...and your off roasting the tires

Sorry for the long post. There are variations of this method. I chose this technique to suit my knowledge, experience, shop tools, and garage space. There are better, faster ways.

 

[goldbomb79]

Drago, not to sound mean, but have you ever seen someone change gears before? Do you have a torque wrench to measure rotational drag so that you know when the pinion nut is tight enough? do you have a dial indicator or a 1" travel indicator? just some basic tools needed to measure backlash and such. I would also suggest a master rebuild kit for the rear. also a traction lock rebuild kit would be a good idea while you're in there. have fun with the crush sleeve because it was a p.i.t.a. tightening under the car. also one more thing. make sure you measure the shim that is under the pinion nut so that you shim the new gear the same. if you need any help I'll try my best. I've installed several sets of gears over the past 5 years so email me at [email protected] if you need some help