915 teeth, pictures, damage, advice needed

[BrokeMyCar]

Hi folks,

My 915/61 is apart - there's some great carnage to justify the rebuild, but before I put in the order for parts I'd love advice about what else I should replace. I have to replace the dog-tooth gear on 1st, and the 1st slider. Does 2nd look like it needs replacements (little bumps on the heads of the teeth?)? What do you guys think of the end of my input shaft? Am I missing anything else?

My symptoms were poor 1st/second shifting, and occasionally a raspiness on shifting to third.

Thanks,

Babak

1st gear, pinion shaft: (about 1/4 missing)


1st gear slider:


2nd gear, pinion shaft:


3rd and 4th, pinion shaft:


3rd and 4th, main shaft:


main shaft input:


main shaft, 1st gear(integral with shaft):


main shaft, 3rd and fourth, zoom in on teeth:

[john walker's workshop]

well, 1 and 2 syncro rings are worn and polished. maybe 4th too, but it's blurry. 2nd teeth don't look too good. the 1/2 shift sleeve may or may not be still good. you need to look at the inside contact surface that rubs on the syncro ring, both sides, and determine if metal has worn away from all the syncro scrubbing it does. same on the 3/4 sleeve which tends to be worse and more obviously worn. so lets see the inside of the 3/4 sleeve. any syncro with polishing on the surface or chunks out of the surface needs to be replaced. the mainshaft end looks like baked on grease and should clean up. what's the 5th gear hub look like? check for notches worn into it from driving in 5th. same on the other two hubs. are the mainshaft and pinion bearing races still tight in the diff housing and center housing?

[BrokeMyCar]

Thanks for the advice John! The main shaft race is fairly tight - I could pull it up with significant manual force so it moved vertically, not laterally. But the metal gasket appeared "punched out" by it, so I bought some thread gripping mixture from Ace, and will apply a coat between the race and the case, before re-assembly.

I know these aren't all the pictures you asked for, but I was being called for a group dinner, and this was all I had time to snap:




Thanks!!

Babak

[john walker's workshop]

also check the tensioning plates that hold down the ball bearings that have a lip. the lip of the bearing should be slightly proud of the face of the plate, not sunken below the surface. that's usually what pounds the shims.

[BrokeMyCar]

I took some more pictures this morning. Ends up I don't have a wrench big enough to open the nut on the input shaft, so I couldn't open up 3/4 yet. I tried to spy some shots of the slider inside anyways.

Also, what do you guys think of my 5th slider? Needs replacement?

The 1-2 slider looks pretty grooved and shiney.

Right now it looks like synchros on 1st and 2nd, 1-2 slider, for sure. Those were the ones giving me trouble.

John, I didn't understand your suggestion about the bearing - is that something I'd see once I open up the gear/synchro assembly?

Thanks!

Babak

5th gear slider:


3/4 slider:



3/4 synchro teeth:



1/2 slider:

[BrokeMyCar]

One more quick question and pic: does this flywheel look re-surfacable or should I just buy a new one.

Thanks-

[john walker's workshop]

toast.

[BrokeMyCar]

Great - thanks for the replacement advice, looks like I'm buying:

1-2 slider
1 and 2 synchros
5th slider
flywheel
transmission gasket set
pinion nut
adjusting shim (found by searching by part number on pelicanparts.com)

Thanks,

Babak

[BrokeMyCar]

Argh. Now I'm rethinking this. The 5th gear slider is $600, and I wasn't observing any problems with 5th gear.

[john walker's workshop]

5th slider looks ok from here. how about the 5th hub? look for notches on the splines where the 5th/rev shift sleeve sits on it when it's engaged in 5th. what's the report on the 3/4 setup? have it apart yet? the 3/4 slider is usually pretty worn where it rubs on the syncros and you can't see the worn part unless you disassemble. looks like at least one of the syncros there is polished.

[Peter Zimmermann]

Make sure that you order a 5th synchro ring to go along with the slider replacement!

Few comments;
1. Have you checked the pinion shaft bearing race in the diff housing? Loose?
2. Have you checked the needle bearing surface of 5th gear? Are there equally-spaced marks that you can feel with your fingernail?
3. Was the large flange nut on the M/S kinda semi-loose? If yes, you must take the shaft's gear stack apart and check all of the surfaces for wear. I see this problem regularly, with wear on thrust washers, etc.

[BrokeMyCar]

I'm gradually learning the names of all the bits! The 3/4 has not been taken apart yet - I'm still short a giant wrench to open the nut. I'm going to put in an initial order today, I'm running near the limits of time/money on this project. I took some pictures of the 5th hub (I think!). Should I take it apart to see the wear you were describing, or is this good enough to tell it's ok?

Peter: Pinion shaft bearing is pretty snug, but can move if really pulled (also evidenced by a "punched out" metal shim). I'm going to locktite it. The large nut on the input shaft (the one with the indent, not with the pin) is still on tight. I haven't opened it up yet. The bearing pictures are below, would love your thoughts.

Thanks so much John and Peter, this is by far the most complicated thing I've taken apart and I'm learning TONS.

I believe this is the 5th hub?



And here are the needle bearings and their mating surface: