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tomek

differential noise

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Viscous lsd in rx7. IRS. It is steady, speed dependent shhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhh noise. I lifted both wheels of the ground, and had assistant "driving" at 50-100 mph when I dove under the car.  Definitely the noise is coming from differential, but impossible to pin-point exact location in the diff. The noise does not change whether you are accelerating or slowing down. I`m thinking carrier bearing(s). Any ideas ?  

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You're probably right, but if it's eating bearings you need to replace them all.  It's not rocket surgery if you have the right tools, but people think you have to have voodoo, Tinkerbell, and say bibbidi-bobbidi-boo while rolling your tongue and standing on your head to set them up correctly.  Might be better off buying an entire unit from a scrap yard or new if you have that DaveK bank account.

Side note:  I would never run a car at 100mph with the wheels off the ground unless it was on a lift. 

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Used one is 500 bucks with S&H if you actually can find it. I already have carrier bearings, I'm gonna get pinion ones before I remove it. Gotta remove entire assembly in order to service it. It is PITA, but you gotta do what you gotta do.

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I agree on checking what's in the oil.  Strain it if it's too dark to identify things.

 

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Oil is nice and clean, replaced every 10-20 k miles. It is weekend, summer toy car. I don't drive it much.

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How many miles are on the rear?  Most never change the rear oil without issues until high miles.

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5 hours ago, tomek said:

Used one is 500 bucks with S&H if you actually can find it. I already have carrier bearings, I'm gonna get pinion ones before I remove it. Gotta remove entire assembly in order to service it. It is PITA, but you gotta do what you gotta do.


That tells you it's prone to failure.  I've had body shops buy an entire front clip for a Focus and the junkyard give them the motor and trans for free because they don't break and it's not worth unbolting it before they cut the front end off.  On the flip side, a non-broken 3.7 in a Traverse is over 2 grand for just the engine because they break daily.

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Well, they are quite bulletproof, it is  Turbo model.  There is demand for Turbo drivertrain.  Lottsa people turbocharge NA models and they need those parts. Differentials from 87-92 Turbos are stronger then  Torsens from 93+ models.

 

Anyway, I`ll deal with that next month , don`t want disabled car in my garage for next couple of weeks right now.

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You never gave a year so I can't try to find you one.  You also didn't say it was an upgrade for a weaker version in another vehicle.  The 350z guys figured out the 370z rear axles and wheel bearings are significantly beefier than the 350z version, and are direct bolt in, so now the parts have been on intergalactic backorder for months.  Nissan can't make the parts fast enough to keep up with demand.  One aftermarket supplier has 100 sets on order and they're all sold.

Clearly "bulletproof" is an overstatement since it broke.  You sure it's not a Ford?

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It is 89-91 TurboII , as far as bulletproof lets not argue about it. Failed bearings after 180 k miles does not really mean weak differential. Keep in mind most turbo rx7s still running operate at much higher then oem power levels. Like 400-500 vs 200-250 hp or whatever Mazda claimed.

 

BTW, 400-500 hp is not much these days but they only weight 2900-3000 pounds.

 

Amyway, I've found required bearings and seals and gonna fuck with that in couple of weeks.

Edited by tomek

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Yeah, the RX7 has a cult following, parts are expensive.  The engines were easy to break (not in the sense of poorly built, but needed exacting care), so lots of cars came off the road and got scrapped.  When I decided mine wasn't worth fixing at all any more I still got decent cash.

 

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Interesting.  Car-part shows that an 87 also fits that car, and a place in California has two on the shelf for turbo locking diff for $125 but no shipping.  There's only 4 in the country and they all show 87-91 fitment.

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87-88 are clutch lockers, 89-91 viscous. LSD on former has probably stopped working long time ago. Rebuild kits are no longer available from Mazda.   Carriers are interchangeable but half axle stubs are different. 

You are buying 30 years old used part, God only knows what is there. I`d rather fix mine, all OEM quality bearings and seals are about 200 $. 

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Pour 3.874 metric ounces of acetone into the gear oil and it'll clean everything out making it work like new.

 

But really, my guess is on the pinion bearings.  I don't know that diff, but from others I've messed with what you describe makes me think pinion bearing.  If it has a driveshaft carrier bearing then I'd start there.

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Pulled out that MFer last night. 3hrs of quality time, laying under, by, near or close to the car.

Today I feel like I was wrestling sea lion yesterday. I need full body massage. lol.

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5 hours ago, tomek said:

Pulled out that MFer last night. 3hrs of quality time, laying under, by, near or close to the car.

Today I feel like I was wrestling sea lion yesterday. I need full body massage. lol.

Welcome to old age.  Still nothing compared to what a lapping day does to me.  I was a whiny baby on Friday at RacerXX.

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24 minutes ago, jon haney said:

Welcome to old age.  Still nothing compared to what a lapping day does to me.  I was a whiny baby on Friday at RacerXX.


But you are coming back next year to do it again, right!

 

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Dissembled it yesterday, pinion was not turning smoothly. There are, going from the front, two ball bearings side by side, and two tapered bearings. One of ball bearings is worn out. Of course it is available only from   mazda . Koyo DG 4077- internet search shows nothing of correct dimensions. The question is should I replace tapered  bearing at the end of pinion shaft as well and potentially deal with gear clearance, or just reuse old one .  I do have all new bearings for pinion and carrier.  

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If you're staring at it out of the car, replace it.  You don't want to put all that back together with all new bearings except for one or two.  That metal is in the bearing and has caused wear on it, so it is compromised.

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Shims are no longer available from Mazda, I will have to fuck with that if clearance is off with new bearings. 

 

Gears are in excellent shape.

Edited by tomek

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On 10/17/2019 at 5:24 PM, John01XX said:


But you are coming back next year to do it again, right!

 

We'll see.

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On 10/19/2019 at 10:25 AM, tomek said:

Shims are no longer available from Mazda, I will have to fuck with that if clearance is off with new bearings. 

 

Gears are in excellent shape.

If reusing the same gears, I wouldn't think a bearing replacement would throw off the mesh pattern enough to matter, assuming the replacement bearing has identical dimensions to the old one, and the mesh pattern was good before dis-assembly.

Edited by jon haney

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It looks like I won't have reshim it, the new tapered bearing that matters is about 0.02 mm taller (width) vs. old one.

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We only have one rule, but how 'bout posting a couple pics?

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