peejay

White Trash finally broke.... and unfortunately, I can't proudly hold up shattered metal and say "That blowed up real good!"

I was driving to Columbus from Cleveland yesterday. Mission was, leave Cleveland at 1, get to my work in Columbus at 3, get home at quarter to 4, install a strut/knuckle/halfshaft assembly in my (parents') Subaru, and kick back and do some heavy duty relaxing.

Instead, not a couple miles off of the on-ramp, I heard a kind of loud thunk-a-thunk. Sounded like a screwdriver rolling around in the back. Kept going. Heard it again. Okay, might be dragging something. Let's just slow down to the berm and have a look.

Hey, what's that loud whining sound?

Nothing dragging. Let's get going again. Hmm, it's quiet under acceleration, but much bearing-type noise under decel. I press on, 130mi from home, and I can't coast or slow down. Perfect. I keep it in 5th and left foot brake to slow down. Seems like I ate the front pinion bearing. (It's the one that is loaded under decel)

Pull off at the first rest stop with a phone. Man it sounds ugly when I downshift (so I can keep pressure on the diff). Coasting to a halt in the parking space, it BANGs and BANGS and BANGS and makes the whole car jerk. It feels like gearteeth out of alignment and binding up.

Uh-oh!

I was an hour late. It took three long, stressful hours wondering if it was going to lock up on me and leave me stranded in the middle of BFN, while I tried hard to never let off the throttle, even in traffic, and panicking at every little noise. (It only thunked one more time on the trip)

Oh well. Looks like I have to put more money into this car... this is really the first mech. failure on the car that isn't a direct result of my messing with it. (Drag racing certainly didn't help) Fortunately there are RX-7's in junkyards 'round here... get me an '84-85 rear with their nice big axles, weld the diff locked, and have some fun.

Max7

you gotta love "strange" noises in the car, ouch.
glad to hear you made it home in one piece, from all the "good" abuse you give it, you should be proud it has lasted this long

peejay

Yeah, really! Actually I expected the driveshaft or the trans to blow out before the diff. I was HOPING the stock clutch and teeny tiny tires would act like a fuse to prevent breakage, figuring that Mazda designed the drivetrain to hold up to all of the abuse that 185/70-13 tires could stand.

Half an hour before I left I was doing 3rd gear burnouts in the rain on the highway. Car going 50mph, tires going, uh, 100 or so More like left rear going 50, right rear going 150!

Hmm, maybe I damaged the side gears. It only makes ugly banging sounds when I'm turning. And then gunk from that damaged the pinion bearing. We'll find out soon enough, it only takes about a half hour to tear the centersection out!

Barwick

you drive from Columbus to Cleveland often? (as in multiple times a week?) That's quite a drive.

sonic_rx7_84

I remember when i had a wierd sound sneak up on me, oh yeah that was my oil line bursting while i was going down the highway at 85 mph. that oil didn't want to come off either.

yayarx7

My funny sound was the rear wheel bearing letting go. I tried to make it all the way to abilene but when the thing started smokin i pulled over.

peejay

Drove it to work fine this morning.

A block from home this evening the rear locked up coasting to a stoplight. Drove it the rest of the way home brake-torquing it in 2nd gear at 20mph.

This sux. I'm going back up to Cleveburg again (yes, I do it twice a week, it's only ~135mi each way) with the Subaru, which may or may not blow up (crosses fingers). I'm bringin' my bike down here so I have a guaranteed way of getting to work, altho my mom says she'll drive me to work in the morning although that also means she has to leave at 6:45 like me instead of 8.

Denny

Peejay...

I have a Lincoln Locker rearend if you want it, and I know where there is a couple of SE's in yards near where I live...

Denny, from the 'ol corncrib....

peejay

Lincoln Locker? That's right up my alley! There's nothin' that a MIG can't fix!

I'll PM you my e-mail add'y, most 'preciative of the offer. (Uh-oh... what year centersection is it? I think I can only use '79-'83 in my housing... I still have yet to check the Mazspeed rearend FAQ)

Denny

Almost certain it's to an early model Seven. Don't think it will fit a later version 1st gen. Came from an SCCA racecar.

Denny

peejay

Denny, please check your PM's! :-)

- PJ (Getting more and more mileage out of the ol' Schwinn)

brownmound

And what did it sound like before it went out? I'm getting squeaking back there (bearings?) but I am also getting a helicopter blade like sound from the back....maybe the bearings, or an unbalanced driveshaft?

Don't want mine to explode...

Right on-

peejay

A deep grumble all the time, changing intensity/pitch with speed, is *usually* an axle bearing.

I drove on mine for MONTHS before changing it. Durn thing was REALLY loud... pull it out and cut it apart (had to, really, to get it off the axle) and there were ugly deep pits in both the inner and outer race. The bearings are *outside* the rearend's oil system, and are the cartridge type like on the front of most FWD's. Land Cruisers are similar, and I saw someone drve on a bad bearing so long that you could wobble the wheel 1/2" up and down, and and it wallowed apart the axle seal! Complaint was squeal from rear brakes... yeah they do that when coated w/gear oil! :-)

brownmound

peejay-
I've been driving on mine for MONTHS also...it does seem to be getting louder. I've been trying to get with my RX guru to help me fix it, but he's been busy. Just worried about the 3 hr drive to Houston and back to Austin.

Of course, the Mound has bigger problems to worry about.

Right on-

pineapple racing

The 79-83 used the smaller spline axles
84-5 big
All the pumkins(rx2,rx3sp,rx7 79-85) will bolt into the other year housings, incl. posi
The companion flange that the drive shaft bolts to vary. With care it can be swapped from any of the above to any. WITH CARE!!!
The axle side gears can be change in the posi to match your axles. Requires disassembling the posi unit. The gears are very expensive to buy new.
The rx2 had 3.70 gears all others 3.90(4.06se)
For you hard core types, the big spline axle rear end housings are NOT as strong as the small. If you drive hard on the street, or track use, check the housing for cracked paint at the end of the housings where it gets bigger to hold the axle bearing. Cracked paint means it is probably bent.Rob

Felix Wankel

Hey Rob are the axles the same diameter, with just bigger splines, or are the 84-5 axles themselves bigger? It'd be kinda cool to hybrid an 83 and 84-5 rearend if it was possible... Stronger housing with the bigger axles

peejay

Evv'rthing is different... axles bigger, bearings bigger...

Epilogue to the long sad story... I yanked the centersection today... YEP it was the full power highway one-wheel-peels that killed it. (BTW the gear oil came out SILVER with metallic crud, yuck!)

The diff spider gears' shaft rotated in the diff carrier, snapping the retaining pin.

A chunk of that pin flew up and over onto the "shelf" in the nose that directs gear oil to the pinion bearings. That is what damaged the front pinion bearing, causing the loud bearing noise on decel.

Without the retainer pin, the spider gear shaft started walking outwards, causing the occasional thunk as it hit the pinion gear and got knocked back into place. Holding power probably helped keep it in place, as that way there wouldn't be constant load reversals helping it walk its way out.

But walk out it did, doing a real number on the pinion gear... it looks kinda like turbo wheels that have suffered a foreign-particle ingestion. It was this that caused the banging, and eventual locking-up on deceleration.

Total tally... diff carrier trashed, R&P trashed, pinion bearings trashed. Basically the only salvageable parts are the housing itself and the pinion flange. Fortunately, the diff I got from Denny (mucho many lots o' thanks!) had the 79-82 pinion flange so it was a direct bolt-in swap. Pics of the carnage are coming

- PJ ("That blowed up real good!)

Denny

Atta-boy, Buckaroo...

Glad to be of assistance....
Denny, from the 'ol corncrib....

REVHED

What's a Lincoln Locker?

Pele

iTrader: (28)

Its not really a differential as it allosw NO wheel slip. It's just a straight driveshaft to axle gearbox. Good and strong as there's nothing to break, but it tears up your rear tires in turns as the outer and inner tires have to spin at the same speed. Not much of a downfall if you're drag racing though.

REVHED

I know what a locker is but I was just wandering about the "Lincoln" part. Is it just a nick-name for a welded up stocker? Over here we call em BOC or CIG (brands of welders) lockers. Speaking of which I've got a spare diff that I'm getting my friend to weld up for me today. Should be fun in the wet.

peejay

Lincoln Electric is a popular brand of welder.

I'd really rather have a locked diff, actually. The tires are always slipping anyway, max traction happens at about a 10% slip ratio and any time power is transmitted, the tires slip. It's how tires work, and why they wear out instead of lasting forever. Wet weather driving is scary with an open diff, you never know if one tire or both tires are going to spin. Will it understeer or oversteer going around this turn?

And, I would like to point out, spinning one wheel is very bad to the health of your differential.

Pele

iTrader: (28)

Is a constant difference on speed, but both wheels still spinning, damaging?

I've always though it best to put the doughnut on the rear to minimize the effect on the steering.

Seems now it should not go on the drive axle.

peejay

Yes, it is very bad!

The spider gears are really small and ride on splash lubrication with no provisions for oil retention. They aren't designed to spin at high speed while power is shuffled through them.

Remember.... I did hundreds of high power burnouts, hundreds of hard launches, and probably thousands of tire-chirping powershifts in the past 40k miles that I've owned the car. What killed the diff? Doing a full throttle one wheel burnout at 50mph. One tire going 50, the other going maybe 100, making a 50mph speed differential going through those little teeny tiny gears while dealing with all of the power my engine can put out.

This is not an uncommon problem. It happens to Saturns and Neons, and Fords and GMs and anything else that has a spider gear type differential. They aren't designed to handle power like that.... the only ones that are, are planetary diffs and those are only good for center diffs on an AWD (they do not have a 50/50 torque split and thus would suck as an axle diff)

IIRC, it says in the FD owner's manual that if a flat occurs on the rear, you put the spare on the front and move the front tire to the rear. However they had really tight LSDs and having a mini-spare on would probably fry it. (Most cars with AWD have full-size spares, or at least mini-spares of the same diameter)

Pele

iTrader: (28)

Anyone ever figure if they could put a full size extra wheel in the doughnut compartment in their 7?

Yould the douchnut be equal to a standard 15 inch rim with a low profile tire on it?