Found my 915 noise source, lots of questions

[yelcab1]

Finally found the reasons for my 915 noise.

1. The inner surface of the input shaft roller bearing is badly pitted. It's hard to see but it is the OD of the inner race.


2. The reverse idler gear surface is badly pitted.


Question 1: replacing the idler shaft is obvious, but should I also replace the surface bearing (not needle bearing) that goes up against that pitted surface?

Question 2: The 2 needle bearings cages inside the reverse gear fall apart very easily, are they bad? I did not see any scoring on the shaft or on the bearings so are they still good?


Question 3: is this input side reverse gear good, or bad?


Question 4. Are these spacers still usable with the imperfect edges?


Question 5: is this 1/2 slider gear usable?


Question 6: is this 5/R slider gear usable?

[yelcab1]

Question 7, The lower bearing outter race on the case can be spun by hand. Is that supposed to be that way? Or, do I need to replace the race and the bearing?


Question 8: This first gear on the input shaft, is that still good?


Question 9: is this input side second gear still good?


Question 10: Gear 1 input side is slightlhy higher 1/16 inch than Gear 1 on the output side, is that normal?


Question 11: notice the input shaft with gears 1/2/3/4 on it, I am not planning on taking them apart because I have no way to put the nut back on. I have inspected the surfaces, the gears, the slider, the synchros, and will clean them before assembly. Is that Ok by most standards?


Question 12: how do I press on the gears on the output shaft without a press?

[Fishcop]

Okay. I'll have a go... But hopefully Grady, Peter Z or JWW will chime in and correct me

I'm just going through this now...

1. Replace roller bearing
1a. Replace idler AND bearing
2. Not sure
3. Looks fine to me
4. Reuse
5. You should replace synchro bands and slider whilst you have it apart (is it a later or earlier box? Because there is a difference in the 1st gear synchro and slider).
6. Looks okay, but how are the reverse teeth?
7. Spinning race IS a PROBLEM - normally requires some machine work and pressing in a 'speedy sleeve'. There are some bearing retaining products from Loctite, but it's a call a professional would have to make.
8. Looks fine
9. Appears fine in the photo
10. They should be even
11. DANGER Will Robinson. You really should disassemble and review the components. Unless you have recorded proof of a recent rebuild, you really should change the 1/2 synchro bands, brakes and dog teeth - 1/2 slider should also be replaced at the same time.
12. To get everything off - Gravity. Heat the four-point bearing race (the small ring holding the roller bearing above it), and then smack the whole thing down on a piece of steel/aluminum plate (I know this sounds brutal, but it is what the pros do!).

To get the gears back on, mine slid most of the way on and then I did the reverse of getting them off...

Like I said, a few of the real experts will chime if for you I'm sure. But I am almost positive they will suggest that you completely R&R the mainshaft. There are quite a few good threads on making tools to do the job without using factory tools (I used an old clutch plate in a vice and a big @ss shifter to undo the 41mm nut - getting it back on involved a home-made 41mm crow foot and torque wrench with additional math to calculate the offset caused by using a crow foot).

I think a gearbox is truly one of those components where you need to be thinking "while I'm in there..."

Good luck

[arbita1]

In regards to your spun bearing you can check out my rebuild here:

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

And here:

915 Rebuild (Part II) - Time for Assembly

[Porsche_monkey]

I agree with Fishcop.

I think #2 is okay.

The loose bearing race clearance should be measured. Peter Z. (much smarter than me) will tell you to get the machining mod done I think. If it is only a small gap, say, 0.0005" I would loctite it. Others here will disagree. If Peter disagrees with me, take his advice over mine.

You need to finish the tear down. If you have no other option you can grab the un-used part of the shaft (NOT the machined surface) in a vice and take the nut off with an adjustable wrench. I do not recommend that method, but it is preferable to just assuming the internals are all good. There are several threads showing the proper way to do it. If you can not get access to the right re-torquing tools mark the nut rotation with a scriber before you remove it, and then re-set it to the same point when you are done. I DO NOT RECOMMEND this method, but it is better than leaving the shaft assembled and hoping everything is good. Since you are in California, not exactly the middle of nowhere, you would be better off to pay someone to help you, or get a local Pelican to lend you some tools.

To get everything off you can pound it on the floor hitting the hard end of the shaft on a steel or aluminum plate. Sounds crazy but John Walker does it that way. I did it last week, it is pretty easy. Post pictures of the synchros and the dog teeth.

If you do not have a press get your stuff organized and go to a machine shop and have them press it for you. Should only take 15 minutes. Worth the time/effort in my opinion. (I stack everything in order on a piece of wooden dowel, then just slide the pieces off and press them on in that order)

P.S. Nice pictures. I can tell from your 'organizational skills' that you will be able to do this.

[yelcab1]

Screw it, I am welding up a socket for the main shaft nut.

Looking for a thow away clutch plate for a holder.

Those pictures were made with Nikon $tuff, so they better be good.

[Porsche_monkey]

Originally Posted by yelcab1

Screw it, I am welding up a socket for the main shaft nut.

Looking for a thow away clutch plate for a holder.

Those pictures were made with Nikon $tuff, so they better be good.

Wise decision. Post pics and hopefully Peter Z will chime in. We are amateurs, he's a pro.

[yelcab1]

So far, no taker on my beg for a throw away clutch disc. Do any of you want to lend me yours?

[Fishcop]

Yelcab, you're in San Carlos... I've got a funny feeling that's where Wevo is located

[yelcab1]

About the spun bearing race.

It moves in and out about 0.050". With my hand, I can spin it in its place with the present lubrication but it does not easily slide out of the hole. With a small slide hammer, it came out eventually.

I measure the hole with a boring gauge and the bearing race with a micrometer and the hole is 0.001 to 0.002" larger than the bearing race ... and once it came out, it is not possible to just slide the bearing race back on dry.

My guess is it is supposed to be interference fit and that is too loose.

Given that situation, any recommendation? Somebody mentioned Wevo ... looked at their web site and saw the retainer plate. Will that work in conjunction with locite?

[Fishcop]

http://www.wevo.com/Products/TransmissionProducts/WevoTransmissionProducts-RaceCaseFinalDrive.htm

[yelcab1]

wow John, that is almost $1,000 for a mod. I think I will look for a different solution first.

[Joe Bob]

#7.....was the cause of my 2nd gear explosion. Get the bearing retainer plate from WEVO or GT/Guard transmission. I machined the case, pressed in a sleeve and replaced the bearing.

DO NOT Loctite it....

[Fishcop]

Originally Posted by yelcab1

wow John, that is almost $1,000 for a mod. I think I will look for a different solution first.

Yep. It is the Rolls Royce fix...

[Porsche_monkey]

Originally Posted by yelcab1

I measure the hole with a boring gauge and the bearing race with a micrometer and the hole is 0.001 to 0.002" larger than the bearing race ... and once it came out, it is not possible to just slide the bearing race back on dry.

Given that situation, any recommendation? Somebody mentioned Wevo ... looked at their web site and saw the retainer plate. Will that work in conjunction with locite?

I think you need it machined somehow somewhere. Loctite will not be permanent, that is too much clearance.

[0396]

Originally Posted by mikez

#7.....was the cause of my 2nd gear explosion. .

DO NOT Loctite it....

Good info!

[yelcab1]

OK Mikez, what machine shop did you use? Care to pass on the info?

Secondly, the good book Bentley does not show a disassembly sequence for the transaxle. Can someone post a few simple steps and things to look out for so that I can assemble the tranxale back together and not changing the shim pack, and not having to measure backlash etc...

[Peter Zimmermann]

Originally Posted by yelcab1

About the spun bearing race.

It moves in and out about 0.050". With my hand, I can spin it in its place with the present lubrication but it does not easily slide out of the hole. With a small slide hammer, it came out eventually.

I measure the hole with a boring gauge and the bearing race with a micrometer and the hole is 0.001 to 0.002" larger than the bearing race ... and once it came out, it is not possible to just slide the bearing race back on dry.

My guess is it is supposed to be interference fit and that is too loose.

Given that situation, any recommendation? Somebody mentioned Wevo ... looked at their web site and saw the retainer plate. Will that work in conjunction with locite?

Loose bearing race - Engine Machine Service (310) 641-7019 - talk with Bill or Dick. Take the housing (they'll clean it), the side cover and a new P/S bearing outer race. They'll machine an insert, install it, and install the race.

Regarding your gears, a camera just can't replace eyes. If there is any tooth root wear (through the hardened surface, usually found on the smaller gear of each gear set) that gear set is a throw-away. (Dog teeth don't matter, they can be replaced). Root wear is most common on 1st, 2nd & 3rd - in that order.

Reverse idler pin - throw away. So are the bearings. Look carefully at the idler gear, where it contacted the flat bearing. There is a good chance that it has wear similar to that on the pin, if it does the idler is also a throw-away.

[Joe Bob]

Aase Brothers.....one of them has a machine shop in Orange County, CA. He did it for me while I waited.

BTW, what year 915 is this? I have an early 915 that has the retainer already in it and was just freshened up. I rebuilt it for a project that didn't materialize due to the economy taking a dive.

Email me, 356 at cox.net if interested. I'm in it cheaper than you'll be with the issues you have.....and it's ready to go. You shouled be able to recover some costs by selling the gear sets. The 7:31 Ring and Pinion is fun even with a high hp motor.....easy swap for higher gearing if that's what you have now.

[yelcab1]

Thanks Pete

How about a dissambly sequence for the transaxle. Anything specific to keep in mind so that it all comes back with the same backlash and shim pack ?

Many years ago, I had a shop replace a cracked transaxlehousing on a different 915, it broke 3 times after that. My guess is they never did the shim pack right. I don't want that for this time.