Found my 915 noise source, lots of questions - Page 3

Peter Zimmermann · 05-20-2009, 06:53 AM

Quote:

Originally Posted by sc_rufctr

Something to consider which hasn't been mentioned is the tendency of the lower five studs that hold the PS bearings
retaining plate to become slightly loose. These studs are constantly submerged in tranny oil and the locking compounds
Porsche used 20+ years ago are not the same as the ones available to us today.

I, for one, have never found a "loose" clamping plate stud, the loads on them must be very low due to the design of the clamping plate. Peter, you must have been tired when you wrote this - there are six studs for the P/S clamping plate, not five.

Regarding different "fixes," the reason that I prefer the machined insert is because:

1. You can control the installation "press" for the insert,
2. You can control the installation "press" for the bearing race,
3. The repair is aesthetically pure (see before & after pics below),
4. I've never found a loose M/S bearing (either size, early or late), so I've not seen a reason to over-kill the modification.

yelcab1 · 05-20-2009, 07:14 AM

Peter Z

I am trying to decide wether to change the bearing that goes into that outter race. Your earlier opinion and JW's earlier opinion is that the roller bearing has little side load so they don't wear out. It's normally the four point bearing that goes first.

If the outer race is 0.001 inch loose in the case, does that cause damage to the bearing to the point of having to replace the bearing?

Is it bad karma to re-use the old bearing race after the machining is done to the case?

It is probably not possible to replace just the outer bearing race by itself, but I'll throw it out there.

This is an education for me. It is not about the money, although part of the DIY thing is to re-use what can be re-used, and replace what has to be replaced. If I just go in there and replace everything then I learn nothing from all this.

Peter Zimmermann · 05-20-2009, 07:55 AM

Quote:

Originally Posted by sc_rufctr

It is probably not possible to replace just the outer bearing race by itself, but I'll throw it out there.

CORRECT!

This is an education for me. It is not about the money, although part of the DIY thing is to re-use what can be re-used, and replace what has to be replaced. If I just go in there and replace everything then I learn nothing from all this.

My biggest fear is the close proximity of the other bearings to the M/S bearing that failed. All of that super-hard metal had to go somewhere before the drain plug magnet caught it, and I think that it's safe to say that some of those little metal chunks passed through other bearings.

If I was rebuilding your trans I would replace all of the bearings, including those for all five loose gears, the diff carrier, and the reverse idler. Could some of them be used again? Sure, but I don't know of a way to be sure which are still OK, and which have been damaged. I always err on the side of future longevity.

yelcab1 · 05-20-2009, 11:38 AM

OK back to work,

How do you get this sucker off?

JIM DRAGTEAM · 05-20-2009, 12:05 PM

Inertia is used to remove that one.You have to put a flat bar of steel in the ground and to carefully grab the pinion shaft and hit it as much as levelled as possible to the steel bar it will be out in 2-3 times.Also a carefull heat with a very small tip of oxy acetylene torch works fine for the stubborn ones if they will be replaced.

Porsche_monkey · 05-20-2009, 02:20 PM

Put it in the freezer overnight if it won't come off, then try again. Heat should be the last resort.

If you do use heat, do it fast and don't let the heat soak into the shaft, that will defeat the purpose.

sc_rufctr · 09:14 PM

Quote:

Originally Posted by Peter Zimmermann

I, for one, have never found a "loose" clamping plate stud, the loads on them must be very low due to the design of the clamping plate. Peter, you must have been tired when you wrote this - there are six studs for the P/S clamping plate, not five.

I was tired when I wrote this post... Thanks for clarifying. (explanation bellow)

The "loose" stud theory was based on some observations I made as I prepared my gearbox for re assembly. As I was cleaning my case I removed all of the studs for the side cover. The reason I did this is because all of the studs were corroded and the four longer studs for the clutch cable bracket and Omega spring were bent which made it difficult to remove the side cover. I have since purchased new studs from Porsche.

After what had happened to my differential I wanted to do the best re assembly possible.

Meanwhile I was cleaning the PS and Main shaft area and noticed one of the 6 studs was slightly backed out of it's thread. I removed that one with the view to cleaning the hole and stud and re securing it. Meanwhile I checked the other 5 in the area (this is why I said 5 in my earlier post) and although they were all the way home they were not as secure as they could have been. So I removed all ten studs and in my opinion they top 4 were OK but the bottom 6 were not as secure as the top 4. All 10 studs came out with no issue...

This lead me to believe that the lower 6 studs locking compound may have been compromised over time by being submerged in gearbox oil.
The locking compound was dark greenish black in colour.

Regardless of the accuracy of my diagnosis it may still pay to check these studs anyway.

Thanks for posting the pictures of the case repair. I found the first one most interesting. It looks like someone spent a lot of time trying to secure that bearing with a punch.

sc_rufctr · 05-20-2009, 07:43 PM

Quote:

Originally Posted by yelcab1

OK back to work,

How do you get this sucker off?

This is the correct P tool for removing these bearings.

This is one of pics posted by Mike "MBEngineering" in another 915 rebuild thread.
(Apologies in advance Mike for pinching this photo)

You could easily make your own if you have access to a lathe but you'd only use it rarely.

Please see link for more photos of this tool.

Getting Ready for 915 Rebuild - It's my turn.

yelcab1 · 08:15 AM

Quote:

Originally Posted by sc_rufctr

You could easily make your own if you have access to a lathe but you'd only use it rarely.

Getting Ready for 915 Rebuild - It's my turn.

I have enough crap in my 2 car garage to serivice my 6 vehicles. I don't have space for a Bridgeport. Would love one, though.

I got the beaering race and the roller bearing off with a puller and some heat from a heat gun. Will try the freezer method the next time (Monkey).

sc_rufctr · 02:49 PM

Do you plan to use the one piece bearing retainer plate?

This one's from http://www.albinsgear.com.au/index.html (Aussie company)

Complete Overkill IMO

Wevo...

Slim, light and well engineered

Modena Engineering is an Australian company that also make a retaining plate very similar to the WEVO http://www.modenaengineering.com.au/index.htm

yelcab1 · 05-21-2009, 02:43 PM

have not decided on the clamping plate, likely no. But, if I did want to use one, I would buy it from Wevo because they re 1 mile from my house.

Zeke · 05-21-2009, 03:05 PM

Quote:

Originally Posted by yelcab1

Aase brothers are out of the bidness (so the song goes).

The business called Aase Brothers Porsche Dismantlers is gone, but Dave Aase has Aase Sales and I think that's where MikeZ went.

Dennis Aase has another business doing race car prep. According to the website, he and his brother Randy own ASSCO Motorsports. I'm sure they do have a machine shop.

yelcab1 · 05-22-2009, 09:47 AM

How do you press in the outer bearing race into the case here for item 5?I am assuming heating the case up with the heat gun, and freezing the bearing race in the fridge?

Peter Zimmermann · 05-22-2009, 10:15 AM

Quote:

Originally Posted by yelcab1

How do you press in the outer bearing race into the case here for item 5?I am assuming heating the case up with the heat gun, and freezing the bearing race in the fridge?

They're usually not tight enough to be overly concerned. A little heat from a Mapp Gas torch applied to the housing should do it. I use an aluminum driver and puck that comes from a wheel bearing race install kit and just push it in.

yelcab1 · 05-22-2009, 10:28 AM

I am having a hell of a time swapping synchro hubs on 1st gear. None of the DIY tool ideas is working out... I guess I will have to find a local gear box mechanic with the right tools.

Peter Zimmermann · 05-22-2009, 11:24 AM

Quote:

Originally Posted by yelcab1

I am having a hell of a time swapping synchro hubs on 1st gear. None of the DIY tool ideas is working out... I guess I will have to find a local gear box mechanic with the right tools.

Every once in a while you will run across one that is so darn tight nothing short of the factory tool will work. Good luck with it!

sc_rufctr · 05-22-2009, 03:07 PM

Quote:

Originally Posted by yelcab1

I am having a hell of a time swapping synchro hubs on 1st gear. None of the DIY tool ideas is working out... I guess I will have to find a local gear box mechanic with the right tools.

You could cut the synchro hub off with a Dremel tool or similar.
Plan the cuts carefully... One cut should be enough to relive the tension so getting it out is easier...
Failing that make a second cut and remove a pie shaped piece and the rest should come out easy.

If you go this way be careful not to cut the gear by mistake.

Porsche_monkey · 05-22-2009, 05:01 PM

Quote:

Originally Posted by yelcab1

I am having a hell of a time swapping synchro hubs on 1st gear. None of the DIY tool ideas is working out... I guess I will have to find a local gear box mechanic with the right tools.

Do you mean the dog tooth? In some cases I have cut the underside away with a zip cut blade then used a thin screwdriver to wedge it off.

sc_rufctr · 05-28-2009, 01:33 PM

yelcab1

Did you get the synchro hub off?

yelcab1 · 05-28-2009, 04:09 PM

Peter, Not yet. I have been on a business trip out of town and am not able to get to it. The last thing I was doing was to try to get the input shaft 42mm nut off. That was when I learned that my welding skills sucked as the home made socket did not hold up to the torque. I need to redo that socket when I get home this weekend, or get a crow foot socket.

Then a massive cleaning project will begin before I put everything back. Looks to be another 2 weeks before it goes back into one assembly again.