OK, I've been reading a few threads about kia's, miata's, B-series etc... I've been wanting 4.88s for a while and hopefully someone can keep me pointed in the right direction.

I have an '83 gsl, so I believe it to be small bearing 3.90's w/ 7" ring. Since I'm on a budget, used is very appealing to me. I'm not going to swap the entire axle to a later model (84-85) for the big bearings, finding one locally would be near impossible.

Can the 7" ring and pinion only from the Kia or miata be installed on my carrier?

Does anyone have one they'd like to sell?

Thanks!

 

pretty hard to come by used gear sets.
i say a b series is your best bet then pay a tranny shop to set it up.

 

PM Wackyracer....he would know what ring and pinion will bolt right in.

 

IIRC, its a mid 90 Kia Sportage that has 4.77 in the front differential. The ring and pinion gears will work from that. Have a tranny shop switch it over as its quite hard for a backyard mechanic to properly set up a differential gearset.

 

Thats what I gather, I know the whole pumpkin will go into the 84-85 'big bearing' housing, I was trying to verify whether the ring and pinion would fit the earlier pumpkin.

I agree that r&p setup should be done by the novice with any expectations of it working for long, but I'm not a novice, I work in a shop that does gear setups, I have the correct tools, and have done about a dozen, though only one as small as this.

 

The ring and pinions are interchangeable on all of the 79-85 RX-7's, 76-78 RX-3's and RX-2's.

 

Yes it will.

Note that 4.88:1 gears were a competition-only gearset, you will never find one in a junkyard (unless you are really, really lucky and some dumbass scrapped an intact race car).

You can always just get the Kia pumpkin, change the differential, and leave the gearset in the case. That will get you 4.78:1 gears, which are almost as good as 4.88:1

The difficult part of setting up a gearset is screwing with the shims on the pinion bearing. The diff bearings have adjusters, no need to keep playing musical shims. So, get the case from the FRONT of a 1st-gen Sportage ('98-02?) and pull the diff out and swap the ring gear onto your small-axle diff.

You'll probably want to reset the backlash anyway. The one that I got had over double the specified backlash, straight out of the box.

 

thats about exactly what I was hoping to hear. I knew I wouldn't find a mazda 4.88 gearset, but might be able to source a kia 4.77 or 4.87 or whatever.


bear in mind w/ backlash, most specs are for new bearings, you have a little more leeway with used bearings.

Usually I use dummy bearings so swapping pinion shims is cake, but I doubt if I have a bearing set that will match the mazda pinion. If you replace the pinion bearing you can grind out the old to make a dummy bearing.

 

Yup on the KIA. I only pay for the ring and pinion including the bearing and collar.

 

Backlash spec is something like .004-.006. Mine was .008. I set it to .003 and use synthetic.

Setting the gears up "tight" helps keep things in line *when* the carrier deflects under load. The synthetic helps keep things cool, so you don't start binding up when it gets hot.

That was something like 8k-10k ago, still humming along nicely.

- Pete (will hit 200k Real Soon Now)

 

Ken, if you can find an 87-88 Mazda 4 by 4 in Alaska you could get a set of 4.44 for damn near nothing.

peejay, I have been told to set them up a bit loose so that when they get on hot (like during road racing) they have a little extra clearnce and do not break teeth.

 

hey Jeb, thanks for the tip. I knew about the b2600 gears, but if I'm changing gearsets I'm goin with one that will work forever. Theres no course up here that 4.88's can't handle. As it is I never get into 4th. I'd like to run most of the course in 4th, so I think they'll work well. I found a few Sportage forums, gonna try to find someone thats regearing lower and might like to sell they're stock take-outs.