915 Rebuild (Part II) - Time for Assembly

[arbita1]

I used a large gear puller to get the speedo ring side off. I used a end cap of a pipe to cover the opening where the flange is installed and give the puller something to push against. Then I used my impact wrench to turn the bolt.

I went to do the same thing on the other side, but I can't find a way to get a grip on the bearing race.

Also, in regards to the case sealant...the manual only indicates to use a new gasket. Is more than that required?

[Peter Zimmermann]

Originally Posted by arbita1

Also, in regards to the case sealant...the manual only indicates to use a new gasket. Is more than that required?

Oh, yeah! My favorite for aluminum cases has always been Curil T. All surfaces should be cleaned with lacquer thinner (or MEK), then a thin coat of Curil to each side of the gasket (don't leave any bare spots) does the job. I have been tempted to use 574 but have not as yet. I'm not sure how it will work with a gasket because everything that I use 574 on has no gasket (cam tower to heads, engine case halves, etc.).

For the diff side cover, I coat the entire o-ring with a thin application of every day dino engine oil, and I use white lithium grease on the outside of the flange seals for installation, and more grease on their inside sealing lip before the flanges are installed.

[Porsche_monkey]

I've done several drip free 915's with Loctite 574. With and without paper gaskets. And one Hudson engine.

Theoretically all you need is the paper gasket. I prefer to be safe and add some sealant.

[Christien]

Originally Posted by Porsche_monkey

Theoretically all you need is the paper gasket.

What "theory" is that? The one that states every single person who's opened that tranny has treated it with the utmost of care and has never made any kind of nick in the original machining, so that the case pieces meet in perfect alignment and won't leak?

[Fishcop]

Originally Posted by Peter Zimmermann

Matt described the reinforcement process, necessary even with the WEVO clamping plate! The good folks at WEVO told me that their plate offers a fix for the NLA double plates used by the factory, but that their plate will not fix the loose pinion bearing race problem.

Hi Pete

This is the bearing race machining fix to the final drive performed by Wevo that I was referring to - not cheap, but obviously solves the problem. http://www.wevo.com/Products/TransmissionProducts/WevoTransmissionProducts-RaceCaseFinalDrive.htm

I can't get that job done here, but I might be able to get a less comprehensive machining job done once I know what to ask for and how to direct my machinist

Cheers

[Porsche_monkey]

Originally Posted by Christien

What "theory" is that? The one that states every single person who's opened that tranny has treated it with the utmost of care and has never made any kind of nick in the original machining, so that the case pieces meet in perfect alignment and won't leak?

Not my fault your car is beat to schit.

[arbita1]

Success! I got the other bearing off. The exhaust clamps I got for removing the dog teeth also works for removing this bearing.

First I broke off the part that holds the rollers so that only the race was left. Clamped the exhaust clamp to the top lip of the race and used my gear puller against the exhaust clamp. Pulled it off with my impact wrench and done.

Here's a shot with the new bearings on.



Next order of business is to put all the bits and pieces back on my differential case and get the differential back in there.

[Peter Zimmermann]

Originally Posted by Fishcop

Hi Pete

This is the bearing race machining fix to the final drive performed by Wevo that I was referring to - not cheap, but obviously solves the problem.

I can't get that job done here, but I might be able to get a less comprehensive machining job done once I know what to ask for and how to direct my machinist

That's beautiful, but a bit of overkill in my opinion - I've never seen a loose M/S bearing outer race. To do the P/S bearing you need to index the bearing opening, machine it to the appropriate size to accept a steel ring, press the ring in with the diff housing heated, then press the outer race of the new bearing into the steel ring. Because I don't do this repair myself I'll decline to tell you the steel grade, or the "press" requirement to put the ring into the housing, then the race into the ring. You'll have to work with a machinist who you trust, then let him take the concept and run with it.

[arbita1]

Originally Posted by Fishcop

Hi Pete

I can't get that job done here, but I might be able to get a less comprehensive machining job done once I know what to ask for and how to direct my machinist

Cheers

Maybe you can call EMS (Pete's place) or California Motor Sports (CMS) and have them give you (or your machine shop) all the info they need to do it. I'm sure they would understand since you live too far to ship it to them (at a reasonable cost).

[Peter Zimmermann]

Originally Posted by arbita1

Maybe you can call EMS (Pete's place) or California Motor Sports (CMS) and have them give you (or your machine shop) all the info they need to do it. I'm sure they would understand since you live too far to ship it to them (at a reasonable cost).

Believe it or not, EMS deals with Japanese customers. You might want to check shipping prices to Los Angeles!

[arbita1]

So I've been assembling my differential case. Putting all the misc. pieces and seals on it before I put the differential back in.

Here's a pic of the new flange seals.



I also put the new shaft input tube and seals in and the clutch release fork.




I can move the clutch release cross shaft up and down after I installed the roll pin into the clutch release fork. Is this right? It doesn't seem right to me and the Bentley manual is kind of slim on details.

[Peter Zimmermann]

NO!!! WARNING, WARNING!!! DO NOT install the M/S seal & guide tube until the trans is done! As you slide the M/S in and out the clutch splines will cut the sealing lip on the seal, and you will have a nasty oil leak shortly after you put it in the car.

The clutch fork will move. However, you are missing a dirt seal at the top of the fork. Check your PET for the part #...

[arbita1]

Originally Posted by Peter Zimmermann

NO!!! WARNING, WARNING!!! DO NOT install the M/S seal & guide tube until the trans is done! As you slide the M/S in and out the clutch splines will cut the sealing lip on the seal, and you will have a nasty oil leak shortly after you put it in the car.

The clutch fork will move. However, you are missing a dirt seal at the top of the fork. Check your PET for the part #...

Ok...so I should take the guide tube off and reinstall it once I have the M/S installed?


I'm looking at the PET and the Bentley manual and I can't find a seal at the top of the fork. I do see a seal, but it looks like it goes on the bottom of the shaft before the spring is installed. Am I reading this wrong?

[arbita1]

This is what I'm looking at.

[Porsche_monkey]

Shouldn't he also build a silicone dam and drill an oil 'drip' hole in the guide tube?

[Peter Zimmermann]

Originally Posted by arbita1

Ok...so I should take the guide tube off and reinstall it once I have the M/S installed?

YES. Wrap the splines with one or two layers of electrical tape, put a very thin layer of white lithium grease on the sealing lip of the seal, and it and the guide tube will slide right on.


I'm looking at the PET and the Bentley manual and I can't find a seal at the top of the fork. I do see a seal, but it looks like it goes on the bottom of the shaft before the spring is installed. Am I reading this wrong?

Order an extra #8 (I've seen that drawing and it's not correct) and install it at the top of the fork, you might have to squeeze it a little...

I do not believe in a "silicone dam," or drilling an extra hole in the guide tube. The latest generation M/S seal will outlive the clutch if it's installed correctly.

[arbita1]

Ok....now we are starting to move.

I got my correct nut today for the M/S and torqued that on.

I put the differential back into the case. Now here is the thing. The factory manual says to torque the side cover nuts to 15 - 18 ft-lbs. I don't have a torque wrench smaller than 20 ft-lbs so I torqued them to 20 ft-lbs thinking that would be close enough.

Not so! I could turn the axle flanges, but the ring gear would not turn inside the case. So I loosened the nuts a bit and then the ring gear could turn freely and feels the way it did before I removed it. I'm pretty sure this all has to do with PRELOAD. How much do I tighten these nuts???

At any rate it's starting to look like a transmission again.

Next question. Before I start putting the gear stacks back in. Could someone give me a quick crash course on what the detents should look like inside the differential case.

[Peter Zimmermann]

Originally Posted by arbita1

Ok....now we are starting to move.

I got my correct nut today for the M/S and torqued that on.

I put the differential back into the case. Now here is the thing. The factory manual says to torque the side cover nuts to 15 - 18 ft-lbs. I don't have a torque wrench smaller than 20 ft-lbs so I torqued them to 20 ft-lbs thinking that would be close enough.

Not so! I could turn the axle flanges, but the ring gear would not turn inside the case. So I loosened the nuts a bit and then the ring gear could turn freely and feels the way it did before I removed it. I'm pretty sure this all has to do with PRELOAD. How much do I tighten these nuts?

You're doing the pre-load test completely wrong. The factory makes a washer that fits onto the axle flange before the flange is installed. When the flange is tightened the washer locks the diff and you can measure diff bearing pre-load using an inch/pound torque wrench (non-click type).

Torque specs should never be exceeded, I highly recommend that you get over to Sears or find a SnapOn truck and buy a 3/8" drive torque wrench tomorrow. You don't want to be pulling studs out of the housing, along with the aluminum threads!

[sc_rufctr]

Originally Posted by arbita1

I put the differential back into the case. Now here is the thing. The factory manual says to torque the side cover nuts to 15 - 18 ft-lbs. I don't have a torque wrench smaller than 20 ft-lbs so I torqued them to 20 ft-lbs thinking that would be close enough.

Not so! I could turn the axle flanges, but the ring gear would not turn inside the case. So I loosened the nuts a bit and then the ring gear could turn freely and feels the way it did before I removed it. I'm pretty sure this all has to do with PRELOAD. How much do I tighten these nuts???

It's great that you're getting things back together and I don't want to appear negative or pedantic but...

I'm concerned that a difference of 2 to 5 foot pounds would stop the ring gear from turning. The side cover has a machined surface on it that mates with the transmission case. Tightening the nuts to 20 foot pounds is above the recommended torque setting but it should not stop the ring gear turning. The worst that could happen (IMO) is that you may pull the studs out of the case.

After reading your post (highlighted in bold txt above) it sounds like you have zero backlash and the ring gear is being forced against the pinion gear when the side plate is tightened against the transmission housing.

The factory manual states that you must check the backlash and pre load after replacing the differential carrier bearings.
To change the backlash you need to change the spacer shims under the differential carrier bearings (your new ones) with different thickness spacers as required. Re assemble and confirm the backlash and pre load...

If you can't do this yourself you may have to get the backlash checked and adjusted by a transmission professional with the correct tools to resolve the problem.

Peter Zimmerman would know for sure but this is an educated (via this site) suggestion from an enthusiastic amateur.

Apologies in advance if this turns out to be a "Red Hearing".

[sc_rufctr]

More info: Tools for checking backlash... (I pinched these off Rennlist)

Peter Zimmerman:

Could you please post some picks of these actual tools if you can.
What's the distance from the dial indicator clamp to the centre of the axle flange bolt?

(I'm making my own)
Thanks in advance.