How hard is it to swap a rear end gear?

[treveiger]

Next summer im swapping my truck from 8 lug to 5 lug, the rear end is out of a 71 cheyenne and im not sure what gear is in it now but i would like 3.08 or something lower like that if its not already and ive heard some people talk about how much of a pain it is and now im wondering myself. Any information or experiences on doing it would be great.
Thanks

[coggonobrien]

it's easy to do it but to get it to last is a differant story. there's an art to getting everything set right. personally i'd just take it somewhere.

David

[Jacfourteen]

I tried it once and it didn't last long....three days later my carrier was sheared into 3 pieces! I ended up getting another rear out of the junk yard that lasted the rest of the time that I had the truck.

[cdowns]

changing gears is very easy you take your rearend drop it off at a pros shop and pickup a day or so later

[redbaron69]

x2 let someone with some experence do it. the end result will be much better.

[bigblock52]

without the right tools it would be difficult. a company called ratech makes a tool thats pretty cheap to set pinion depth if you want to do it yourself. If you dont have a dial indicator and mag base, yoke holding tool, large torque wrench, and inch pound dial torque wrench I would think it would just be cheaper to have it done unless you plan to do this kind of job alot. best of luck!

[Valhalla]

I am debating the same thing right now. Did it with my dad a few times years ago and the rear's are still running strong. I am thinking I may just bite the bullet and pay for a pro to handle this one being I am sticking a 600hp motor in the truck would prefer not to detonate the rear end. LOL.

On that note anyone know of a good place in AZ to get a rear end done.

[c10seconds]

Originally Posted by Valhalla

I am debating the same thing right now. Did it with my dad a few times years ago and the rear's are still running strong. I am thinking I may just bite the bullet and pay for a pro to handle this one being I am sticking a 600hp motor in the truck would prefer not to detonate the rear end. LOL.

On that note anyone know of a good place in AZ to get a rear end done.

Az differential specialist in phx is a pretty good place
Posted via Mobile Device

[Valhalla]

Originally Posted by c10seconds

Az differential specialist in phx is a pretty good place
Posted via Mobile Device

Thanks I have never actually paid to have a rear end built but I am sure its not cheap I'll call them and get a price Frame goes in for powder coating in a bout 3 weeks so that would be the perfect time.

[HOGDADDY]

I bought new Eaton posi unit, new 3:73 richmond gears + install kit, new axle seals and new u-joints. It cost me around $800 for parts alone.
I was gonna attempt doing the install but the thought of ruining $800 in parts made me uneasy so ended up paying one of the best shops in B'ham to do it Hesco. It wasn't cheap (I am ashamed to say price ) by no means but I have peace of mind that its done right,

[treveiger]

Is it exspensive to have done? Whats the average cost to have it done?

[Valhalla]

Originally Posted by treveiger

Is it exspensive to have done? Whats the average cost to have it done?

Local place called Chandler speed shop told me I would be better off buying a whole new custom build rear end from Currie. They said after parts/time rebuilding my current one will only save me a few hundred over going with a custom high horse power set up. Which was around 2k

[tonypaul]

I would try to find another complete rear axle with the gear ratio you want. It may take awhile to find the right one, but there out there..... ALOT cheaper and easier to swap out! Just my advice!

[Valhalla]

for me its more about not breaking stuff. My motor will be in the 600 hp range. I have no idea what's currently in the rear end of my truck so that scares me.

[treveiger]

next time i go out to the farm ill have to see what kind of rear end is it. The truck had a 350/350 combo im pretty sure

[raycow]

I tried it once, spent hours on it, got a perfect looking contact pattern, and it still made noise anyway. I haven't done another one since. Keep looking until you find a complete rear with the gears you want. It will be better and cheaper in the long run.

Ray

[Shaky]

I put 3.07 gears, Eaton cone-clutch posi, and new bearings in a 12-bolt. It took a lot of time and specialized tools.

There's really only four things to do, but they have to be right:

1. Set-up the pinion bearings (this rear uses a crush-sleeve, if you blow it you have to get another one and start over).
2. Set pinion depth (distance from centerline of ring gear to face of pinion).
3. Set backlash (shim carrier bearings until you get the right number).
4. Check patterns.

If you don't have the right tools to use the carrier bearing diameters in the housing to establish a centerline and then measure from that centerline to the face of the installed pinion, you can't do the rest.

This took me a good month or so of tweaking during the winter (I've been accused of being a bit paranoid). 10K miles so far with no problems.

[Fitz]

Originally Posted by treveiger

Next summer im swapping my truck from 8 lug to 5 lug, the rear end is out of a 71 cheyenne and im not sure what gear is in it now but i would like 3.08 or something lower like that if its not already and ive heard some people talk about how much of a pain it is and now im wondering myself. Any information or experiences on doing it would be great.
Thanks

Getting the correct shim thickness between the pinion and pinion bearing is the hardest part. I used a 12 ton hydraulic press to remove the old bearing and press the new one on, so this isn't something you want to be doing by trial and error. I had a local machine shop take a few thousandths off a new pinion bearing so it was a loose sliding fit on the pinion. Then I could place the shims, re-install the pinion without the crush sleeve and check pinion depth with a dial indicator. When you finally have it right, remove the pinion and the slip on bearing, press a correctly sized bearing onto the pinion using the shims you had under the slip on. Then you can install the correctly shimmed pinion into the housing with the crush sleeve and torque to spec.
Next, start setting the backlash using shims between the case and axle bearings. You'll need to grease the ring gear with a colored(I used yellow) grease to check pattern as you do this. A 12 bolt needs to be between .005 and .010 in of backlash as measured on a dial indicator. I didn't take a month doing mine... and that's not a criticism of anyone posting here. This was the 12th one I've done and practice makes it easier. Just be prepared to spend at least a day. That's how long number 12 took to get it to my liking and if you haven't done one before, take your time. In almost every car club there is someone who knows how to do this. If you can't find a club go to the vocational arts teacher at your local highschool or junior college. When you finally get the gears patterned correctly the pinion will leave "half moon" marks on the ring gear that are approximately centered in the teeth. The last photo is my 12 bolt after I was satisfied. It now has 5000mi and 14 passes at the drags behind my ZZ572 powered 67 stepside. That's 620 HP and it isn't broken yet!

[Valhalla]

Good Info Fitz. I can see my future and it looks like a mechanic doing my gearing.

[71meangreenc10]

Originally Posted by treveiger

next time i go out to the farm ill have to see what kind of rear end is it. The truck had a 350/350 combo im pretty sure

That should have a 3.07/3.08 rear if it came factory. Check the spid to be sure.

If you dont have the tools or knowledge leave the gears alone it is a hard lesson to learn. If you have a 3.73 rear and go to a 3.07/3.08 the carrier has to be changed if you rebuild it.

Smitty

[treveiger]

Thanks guys for all your help, i sure hope it has the lower gears in it. This is a lesson i dont want to learn the exspensive way ive had enough of them already.

[Hart_Rod]

Originally Posted by Fitz

Getting the correct shim thickness between the pinion and pinion bearing is the hardest part. I used a 12 ton hydraulic press to remove the old bearing and press the new one on, so this isn't something you want to be doing by trial and error. I had a local machine shop take a few thousandths off a new pinion bearing so it was a loose sliding fit on the pinion. Then I could place the shims, re-install the pinion without the crush sleeve and check pinion depth with a dial indicator. When you finally have it right, remove the pinion and the slip on bearing, press a correctly sized bearing onto the pinion using the shims you had under the slip on. Then you can install the correctly shimmed pinion into the housing with the crush sleeve and torque to spec.
Next, start setting the backlash using shims between the case and axle bearings. You'll need to grease the ring gear with a colored(I used yellow) grease to check pattern as you do this. A 12 bolt needs to be between .005 and .010 in of backlash as measured on a dial indicator. I didn't take a month doing mine... and that's not a criticism of anyone posting here. This was the 12th one I've done and practice makes it easier. Just be prepared to spend at least a day. That's how long number 12 took to get it to my liking and if you haven't done one before, take your time. In almost every car club there is someone who knows how to do this. If you can't find a club go to the vocational arts teacher at your local highschool or junior college. When you finally get the gears patterned correctly the pinion will leave "half moon" marks on the ring gear that are approximately centered in the teeth. The last photo is my 12 bolt after I was satisfied. It now has 5000mi and 14 passes at the drags behind my ZZ572 powered 67 stepside. That's 620 HP and it isn't broken yet!

Good info. Make sure you mark the carrier caps. They need to go back on the correct side and in the correct up and down orientation. Ask me how I know......