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PPF Bolt spins at Diff

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#1
Sphinx

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So, looks like this is a common issue, but I can't figure out how to fix it.  The front bolt at the diff and powerplant frame (the one with the sleeve) is spinning and I can't get it to torque down.  When I try to take it off, it spins the other way and there isn't a way to "grab" it that would work to get the top nut to seat properly.

 

What do I need to do to torque it down?

 

I never took it off, but loosened it enough to move to the PPF out of the way when I dropped the trans.



#2
FTodaro

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Use an Impact wrench so that overtakes the speed of the lock nut above and if that does not work you should be able to get a small set of vice grips on the locking nut and use the Impact.


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#3
davew

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Use a pair of pliers to hold the "nut" and spin the bolt off with pliers. Then chase the threads on both the nut and the bolt.

You can buy a new bolt, but the nut is only available new as part of the PPF for big $$$$$.

Make sure to re-torque all the PPF bolts after an initial test drive. they have a tendency to come loose after everything finds its happy place.

Dave

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#4
Sphinx

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I'll give it a shot - I'll try it with some vice grips.  I had already tried to use an impact, as FTodaro suggests, but it didn't work.  



#5
Chris D.

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What a coincidence!   I was fighting with this very thing last night.   I took a close look at the nut and it actually looks I cross threaded it.  So the nut wasn't being drawn straight down into the PPF....it was hopelessly crooked and couldn't grab.

 

I was planning to order a new nut and bolt from Mazdaspeed.   Now I see that it's only sold as part of the complete PPF........argh!

 

I found some on eBay.....in "good" used condition.  


Chris Dilluvio

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#6
davew

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I save these nuts from parts cars and carry them in the spares box to the track. Bet bet Drago has a 5 gallon bucket of them.

 

I remember a few years ago, standing in the pit lane with 2 other prep shop owners. A car cam down the pit lane making a ting ting ting sound as something draged underneath. Knowing the trans was just changed in the car, the three of us looked at each other and said "PPF BOLT FELL OUT" since we all had experienced it. ALWAYS retorque the PPF bolts after a road test and after the first on track session. I do!!!!

 

Dave


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#7
Sphinx

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I still can't get this stupid nut or bolt off.  Just spins - might need to soak in some liquid wrench.  Separately, I need to drop the diff to do some maintenance.  So, I have to drop the PPF with it.  What's more likely to be stripped, the PPF or the nut? If it is the nut, obviously I need to find a used one.  If it is the PPF, how do I fix that?

 

Dave, I found an old post that indicated that you sell new PPF nuts.  I can't find them on your site.



#8
Ron Alan

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Give me a call...I will get you parts you need. The aluminum block the mushroom nut pulls into has lost its bit and is allowing the nut to spin.

Try to get a vice grip on the mushroom nut as hard as you can...you should be able to get the bolt off then.


Ron

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#9
Bench Racer

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What's more likely to be stripped, the PPF or the nut? If it is the nut, obviously I need to find a used one.  

 

If it is the PPF, how do I fix that?

 Not that I've changed many PPF, except I feel/hold nut with fingers so I have a clue if the threads are starting proper and if the nut spline is catching the spline in the spacer and the nut is being pulled into the spacer. Included is a video of PPF removal which may be brain food.

 

With PPF out from under car if spacer splines are ruined (or nut splines are ruined) and will not hold nut from spinning and provided the PPF holes are not egg shaped sloppy, one could put flats on both sides of the nuts heads and weld two flat aluminum pieces to the PPF. For location of flats on nuts view video at 7:14 which shows splined nuts anchored in splined spacer (maybe one spline is _ucked up), with nuts in this position mark nuts where flats parallel to length of PPF are required. Weld flat aluminum leaving slight/minimal/just enough side clearance to flats on nuts so the nuts may be removed and replaced. 

 

Yep, rule change required to make legal. On the other hand, whose going to catch a repaired PPF?


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#10
Bench Racer

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Ron, clean your pm box.  Your "aluminum block" is steel. ; )


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#11
Ron Alan

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I always wondered why that aluminum looking piece felt heavy  :wacko:

Is the ppf aluminum?  :help:  :optimist:


Ron

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#12
callumhay

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If you are having a hard time finding a PPF, try Craigslist. Find the local Miata dismantler on there and call him. Typically they have them lying around as it's not a common thing people are after.

#13
Bench Racer

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Is the ppf aluminum?  :help:  :optimist:

Dose it take two men to lift the PPF? :bigsquaregrin:


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#14
FTodaro

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I still can't get this stupid nut or bolt off.  Just spins - might need to soak in some liquid wrench.  Separately, I need to drop the diff to do some maintenance.  So, I have to drop the PPF with it.  What's more likely to be stripped, the PPF or the nut? If it is the nut, obviously I need to find a used one.  If it is the PPF, how do I fix that?

 

Dave, I found an old post that indicated that you sell new PPF nuts.  I can't find them on your site.

I had one that the top nut would just spin and i could not back the bolt off. I took a dremel with a cut off wheel on it and cut off two small sections off it, parallel to each other so i could get a set of vice grips on it solid and back the bolt off. It took awhile but that worked.


Frank
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#15
davew

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Many years ago, I had some PPF nuts made. Now with the popularity of Miata specialty used parts sources, these nuts should be easily obtained.

 

You should be able to grab the nut with a pair of pliers and spin the bolt off. If not, remove the diff assembly with the PPF attached. A real PITA, but we in the rust belt have to do it regularly. With everything on the ground it should be easy to remove the nut and bolt.

 

The nuts are not available from Mazda, but I am sure East street or Planet Miata or Treasure Coast can supply used ones. I make it a policy to always run a tap through those nuts, to chase the threads. The knurls really are just there for assembly line use. They make life easier, but are not required.

 

Any time the PPF is removed, retorque the 4 bolts after the first test drive, then again after the first track session.

 

Dave


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#16
Bench Racer

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Rust belt bolts and then.

 


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#17
manthony121

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This discussion relates to a question I have regarding the upper nuts/spacer on the diff end of the PPF.  The video in message #9 shows the mechanic doing what the factory service manual says specifically NOT to do: remove the upper nuts from the PPF.  In fact, the FSM says that if the nuts are removed from the PPF, the entire PPF must be replaced!  That seems a little extreme.

 

I don't know a lot about cars, but I did well in college physics.  I can't imagine a reason why removing and replacing the upper nuts would make the entire PPF unusable.  They are just press fit nuts and a spacer, right?  They were separate pieces at the factory, so why can they assemble them but the garage mechanic can't?  Is it just that if they get popped in and out enough times, they will get "sloppy", and won't hold any more when you torque the bolts?

 

I also don't understand the sleeve that fits inside the upper part of the front hole (not the one at the bottom that gets pried out).  The FSM says to thread a bolt into it a few turns, then pull it down.  When I tried to do that, I'm pretty sure I was threading into the upper nut.  Nothing was pulling down, and when I pushed up a bit, the upper nut popped off, with the bolt threaded into it.  The car is a 1991, and I'm sure the PPF has been off and on a few times.  Is it possible the upper sleeve isn't there?  Can that be replaced without replacing the entire PPF?  If it is there, is it threaded the same size as the upper nut?  How many turns of the bolt do you need before you start threading into the nut itself?

 

I am not sure about the upper/forward sleeve, because I have not been able to remove the differential mounting spacer that fits between the lower part of the diff and the lower lip of the PPF.  Hence I have not separated the PPF entirely from the diff.


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#18
Walter Vetter

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The splines on the nuts do not engage with the PPF, rather they secure into the block that sits on top of the diff. There is a sleeve that runs inside the front hole of this block and the inside of this sleeve is threaded. A larger diameter bold is required to thread into this sleeve in order to pull it down and release it from the block. Unfortunately if the diff has never been out of the car or not for a long while this sleeve will corrode in place. Note, there is a small perpendicular threaded hole in the hex-shaped diff mount. A small bolt can be threaded in to hold the sleeve in place on re-assembly.

 

I've always just threaded the mounting bolts into the nuts and knock them out of the PPF - I don't have the patience to follow the FSM. I've had the diff in and out of my car more times then I would wish, and have never had an issue with re-installing and tightening the nuts.


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#19
manthony121

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I've always just threaded the mounting bolts into the nuts and knock them out of the PPF - I don't have the patience to follow the FSM. I've had the diff in and out of my car more times then I would wish, and have never had an issue with re-installing and tightening the nuts.

That seems to be the common practice, which makes me wonder why the FSM says not to do it, with no explanation of why not.


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#20
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That seems to be the common practice, which makes me wonder why the FSM says not to do it, with no explanation of why not.

I am guessing but if you look at the round nut the splines that hold in in place are not substantial, and if you keep removing them they may not hold when your trying to disassemble them from the PPF the next time, that is what happened to me, they would just spin when i was trying to remove the bolt.

 

The other guess is, that since they do not sell these separate from the PPF they don't want you to lose them or you will have to buy the PPF to ge them. :)


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