advice of my busted rear end

This afternoon’s project was to investigate the excessive axel end play. I pulled the axel with the intent of changing the axel bearing. I swept the inside of the housing with my finger and found a piece of gear about a half inch by two inches. When I pulled the axel on the other side I came up with another piece of gear. I pulled the gear set and there are two teeth broken off the pinion, oddly 180 degrees out. Upon inspection with the naked eye there is not a scratch on the ring gear, it looks perfect.
I do not really know much about gears as will become obvious with my following questions.

Is it possible to replace just the pinion or is that stupid?

Is it possible to even buy just a pinion?

This is a 5.12 r&p, is the pinion different in a 5.12 vs a 4.88 or a 4.40.

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This afternoon’s project was to investigate the excessive axel end play. I pulled the axel with the intent of changing the axel bearing. I swept the inside of the housing with my finger and found a piece of gear about a half inch by two inches. When I pulled the axel on the other side I came up with another piece of gear. I pulled the gear set and there are two teeth broken off the pinion, oddly 180 degrees out. Upon inspection with the naked eye there is not a scratch on the ring gear, it looks perfect.
I do not really know much about gears as will become obvious with my following questions.

Is it possible to replace just the pinion or is that stupid?

Is it possible to even buy just a pinion?

This is a 5.12 r&p, is the pinion different in a 5.12 vs a 4.88 or a 4.40.
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Stupid? Eh, not wise.

Don't think so. Gear sets are usually lapped in as a set when manufactured.

Yes. The tooth count is different.

Quote:

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This afternoon’s project was to investigate the excessive axel end play. I pulled the axel with the intent of changing the axel bearing. I swept the inside of the housing with my finger and found a piece of gear about a half inch by two inches. When I pulled the axel on the other side I came up with another piece of gear. I pulled the gear set and there are two teeth broken off the pinion, oddly 180 degrees out. Upon inspection with the naked eye there is not a scratch on the ring gear, it looks perfect.
I do not really know much about gears as will become obvious with my following questions.

Is it possible to replace just the pinion or is that stupid?

Is it possible to even buy just a pinion?

This is a 5.12 r&p, is the pinion different in a 5.12 vs a 4.88 or a 4.40.
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yup, R&Ps are machined as a matched set. i doubt you can buy just a pinion new, but you could of course find one in a junkyard. i certainly wouldn't recommend using anything other than a matched set unless you get caught out at the track and are forced into it.

+1, Dick. These are items you want to replace as a set. You "can" replace one of them, but don't make it a long-term solution (and plan on the replacement part junking the old part...) - GA

Dick The R&P are available form Mazda Comp Motorsports. I see on website they have a "Sale" on Competition parts which I would think would be a comp part. They don't last long when posted for sale. I least with 1st gen they are bolt in (I Think) . Good Luck I guess if anything is better to have found in the Garage and not at Speed and have it let go. Tom Weaver :eclipsee_steering:

Thanks, I received the answers I expected. If another set does miraculously appear locally I will take advantage of the sale. If I remember the 5.12 was more expensive than the others so I will need to decide which ratio. I am the only guy locally who has been running the 5.12 and there are a couple of places where that is an advantage although I am sure there are some place where that hurts me.
The odd part is the two teeth that are broken are 180 degrees out and that there were no symptoms at all. God know how long it has been like this.

Dick, look in the garage section at ISCRACING.net. They have a 5.12 and a 4.8 unit. Both are 800.00 with the LS unit. Something about big axle. Hope this helps.
Chris Howard

thank's chris good tip. I did not think the center section was different for the big axel housing but that is what I have anyway.

I called ISC and ordered the used 5.12. When I called they said they had just read the post and were looking up my phone number to call me.

Thats pretty funny.

"Dick Patullo?"

"Yes, who is this?"

"This is Mike calling...I have your new rear end......."

Dick, did you talk with Mike about causes for the pinion teeth to got to hell at 180* apart ? Any ideas ?

No David I did not. I will show the parts to some people brighter than I am and see what we can learn. It is interesting also that there were no symptoms at all. I had never pulled the center section on this rear before and it might have been like this for a long time. Thinking about it this may be the only part of the car I have never looked at since I bought it in 1998.

Dick, keep the teeth parts also so I can look at them. - Greg