Hi Everyone,

I am currently rebuilding my 901 transmission and a few members from the Pelican Parts forum suggested I direct my questions here towards Dr Evil and other folks who have done some DIY work on the 901/914 trans.

I purchased Dr Evil's DVD and tore my transmission down accordingly. I was able to briefly drive this transmission and it seemed to work great, but I needed to reseal it and swap fifth gear. Upon tear-down the dog teeth look very good on gears 2 through 5, but 1st gear does have some wear. The synchro bands have some wear on the moly coating in the first three gears with 4th and 5th looking excellent. My plan was to replace the dog teeth on first gear and the synchro bands on 1st, 2nd, and 3rd. This leaves me with the shift sleeves. I personally thought all three sleeves looked pretty good. Minimal wear, sharp teeth, and no metal smearing, but a few Pelican members feel that if I am going to replace any synchro bands, I need to replace the accompanying shift sleeves. This has led me here.
I have no problem replacing any worn parts, but do not want to discard any pieces that have good usable life left in them. With that in mind, I am hoping Dr Evil and any other members that have experience with the 901 can chime in on the condition of the shift sleeves from a few pictures and help me determine a course of action. I have also attached a photo of the 1st gear dog teeth and a worn synchro band to illustrate some of the wear on these items that I think requires replacement.

Any help would be appreciated.

-Joe

1st/reverse sleeve




2-3 shift sleeve



1st gear dog teeth


Synchro wear

Nice task. I always thought you replace sleeves when you replace synchros. Once you have it apart, why not?

2-3 shift sleeve has some wear. I'd replace it but would defer to @Dr Evil

Can't tell from photo what the orientation is but it's not uncommon for 2nd gear to take the hardest hit as people try to rush the 1-2 shift trying to act like they are racing. Wear has everthing to do with what sort of driver has used the transmission.

I've seen far worse with respect to engagment teeth wear. But, given that it is apart and that parts are readily available, I'd replace the 2-3 slider. That's just my opinion.

I just recently tore down a tail shift so another memeber could have the case and I looking for salvage parts. It was a complete mess. These parts look really good to me right now. Reverse idler was chipped. 1st gear engagment teeth were gone. 2-3 shift sleeve heavily worn. 4th gear engagment teeth were nothing but nubs and the 4-5 shift sleeve was shot on the 4th gear side. About the the only thing salvageable was the gear pairs and bearings.

You've definately got a good core to work with.

Change 1st teeth and band. Put 2-3 sleeve on 4-5 with more worn end pointing at 5, put 4-5 sleeve in 2-3 with more worn toward 3. 1st slider is mint. All covered in the DVD
Don’t change sliders just because. People love to throw money away so that they feel better. It’s not necessary. They either work or they don’t.

Btw, good job on taking the pictures on these parts. We can really appreciate their condition, which seem very desirable compared to a lot of the used boxes out there...
Good luck with your fun project

Oh... and

Thanks for the feedback everyone and making me feel welcome. I have a better idea about how I will proceed with this box now. Hopefully these photos and discussion will help others to determine the conditions of some of their wear items in the future. Cheers!

Joe

Bob B

WORD

Quick update

I ordered the wear items that needed replacing and am preparing to reassemble the gear stack. I acquired an alternate 5th gear that has new dog teeth on it, so I had planned to swap the excellent dog off of my old 5th gear to be reused elsewhere, but upon removing it from the gear I noticed what seems to be a small crack in the backside that fits against the gear. Do these tend to crack or is it possible that this is some sort of casting imperfection? My gut says to toss it. What do the experts say? I have tried to photograph this as best as possible, but it is quite small...

This is a tough call. Hopefully @Dr Evil chimes in.

From photos its a bit hard to tell but here's what I think I see.

Looks like a forging inclusion defect that was in the gear blank before machining and heat treat. When I look at the picture circled in yellow, 99% of the machine marks appear to be intact, and following the same pattern and arc before and after the are lost over the inclusion. To me this indicates it has been there all along.

There is one that seems to be a little wavy but it might be an optial illsusion and/o resolution of the photos. The machine mark in red seems a bit off as it it moved after the fact.

Click to view attachment

So if it was there after the gear was forged and there when it was machined and then heat treated, it probably isn't an issue since it has survived this far.

Now for the question to stir the pot. Would I replace it? Yup, I would time and money not being part of the consideration. Given the effort going into the rebuild, I'd want to know that the the gear is 100%. That's my opinion.

Now let me present counterpoints for reuse as-is as a low risk propisition:

1) It has survived this long and from what I can see I don't see any initiation or crack propagation.

2) I'd do a dye penetrant test. If no cracking has started, then I'd feel really good about reusing it and thinking that it was a defect that has been there all along and hasn't been an issues. A dye penetrant kit is about $130 and will do lots and lots of parts so not really cost effective for you for single use but chances are you have a machine shop around that can do it for a fraction of that cost.

3) 5th gear isn't highly stressed mechanically speaking. Would be way more concerned on 1st gear.

4) The defect is in the middle of the "meat" of the gear body that isn't highly stressed like the gear teeth. I'd be a lot more concerned it it were at the root of a gear tooth.

Let the games begin.

Superhawk,

Thanks for the thorough response. To clarify, this is the synchro hub (aka dog teeth), not 5th gear itself. I think it looks worse in person than the photos are able to capture. By my eye it seems like it may extend to the edge of the teeth where I can just catch a fingernail in it. I'm with you on this one; the gearstack is completely apart and now would be the time to change it. Plus it will give me peace of mind.

Nah, that’s a factory defect. Use it as it’s a low stress point and well fortified and not linear or contiguous.

Thanks Doc. I appreciate you sharing your expertise.