915 won't go into reverse

[cowtown]

OK, I put the nose cover back on, and Reverse was blocked again. So I started looking inside the cover.

After wiping up a bunch of oil, I finally saw that there was a little chunk of metal embedded in the aluminum case.

The chunk was stuck right where the 5/R selector fork tries to move to engage Reverse. It was pounded into the aluminum of the nose cover, so that's why the magnet on a stick didn't get it.

There are grooves in the little metal piece that look machined. Any idea what it is?

[ChrisBennet]

They look like threads to me. Measure the pitch and you can narrow down the possible sources. I.e. pitch=1.25m would be an 8mm fastener. Looks a lot like part of one of the big nuts but that doesn't make any sense to me.
-Chris

[john walker's workshop]

that would be a fairly large nut. better pull of the center housing and the side cover to see more.

[ischmitz]

That is a part of a synchronizer ring. Look at the profile on the outside. You'll need to investigate all five gears to see where it came from.

Ingo

[exhaustfumes]

having just rebuilt my 915, i recognize that blob as a synchro ring. or maybe a brake band. either way, you are on the right track, and will find shifting into one of your 5 forward gears will soon be improved.

[cowtown]

Originally posted by ischmitz
That is a part of a synchronizer ring. Look at the profile on the outside. You'll need to investigate all five gears to see where it came from.

Ingo

It looks like you're right Ingo, but I'm still confused. All 5 synchro rings look intact...? Top picture is the fragment I pulled from the nose piece on top of 5th gear synchro ring....

[ischmitz]

Maybe a previous rebuilt.... What is the history on your gear box/car?

[john walker's workshop]

is 5th galled, or is it the lighting?

[cowtown]

Originally posted by john walker's workshop
is 5th galled, or is it the lighting?

John, I'm not sure what galling means. The gear looks OK to my untrained eye. I attached a couple more pictures with better lighting.

Ingo, the box was a rebuilt unit I bought from a guy in SoCal about a year ago. I have no extensive history on it, but it has been running well. I've been pumping a bunch of power through it, and admittedly shift it faster than I should sometimes. (I won't be doing that anymore ). I can't complain about the broken synchro, unless it really was left in there accidently.

I'm debating with myself now about whether I should pull out the two shafts, and have a really close look. Any advice welcome as always.

[ischmitz]

Colin,

You should be able to see if a chunk of synchro ring is missing at any of the five forward gears. If not it obviously was left behind during (one of) the previous rebuilt(s).

Now that you have torn the box apart I would check the condition of the synchros and the dog teeth and replace what's worn. That said it the stray piece could have caused a lot more damage than just preventing you from shifting into reverse. I did my 7/31 915 and have since driven almost 15000 spirited miles with the 3.6. Against what everyone predicted it is holding up just fine so far.

Cheers,
Ingo

[rcecale]

WOW! Serious deja vu going on here!

Colin, I agree with Ingo. Definitely a piece of a synchro. The good news: It's not part of one of yours (According to what you can see.)
The bad news: It's most likely from a previous incident, with a previous owner of the tranny. And, since you don't know the history of it, I would certainly recommend springing for the cost of the tranny gasket kit and open it the rest of the way and have a look at 1st thru 4th.
Best to have the piece of mind, while you're in there, than to have this running through the back of your mind.

Just my $.02.

Randy

p.s. Great pics!!!

[cowtown]

Originally posted by rcecale
WOW! Serious deja vu going on here!

Randy, I'm finding your gigantic 915 rebuild thread very helpful.

You guys are right, of course. It's hard to overcome the "quick fix" temptation, but I'll pull the shafts and do it right.

While I'm in there, what do you think of doing the WEVO bearing retainer? Is this a necessary update for use with an engine that's putting out about 260HP?

I don't have the low-end torque of some of the 3.6 beasts here on the board. I don't mind buying the part, but only if it is solving a real problem in my particular case.

[ischmitz]

Colin,
I don't think it matters at which RPM the torque flows through the box. But as I said before, my 915 is holding up pretty well to the 3.6 after about 5 track events and 15k miles of street. IMHO it all depends on how you drive and how often you visit the track. Dragstrip behavoir and bad shifts and temps kill a 915 no matter how much it is reinforced. I try to avoid that.

Ingo

[wevoid]

Ingo,

Actually it makes a huge difference at which rpm the torque is put in the transmission, 200 ft/lb at 2000 rpm is not the same a 200 ft/lb at 4000 rpm.

However, I agree, the bearing retainer plate is not an upgrade that will offer an advantage in isolation. If your original unit is worn out - which is not uncommon, then the new single piece bearing retainers are an improvement worth looking at - as a replacement part.

I also agree that sympathetic driving is the best protection !

Regards

Hayden

[cowtown]

Well I thought it was about time to give an update. I just haven't had time to get out there and work until the job was done, so I've been putting in and hour here and there. The 915 is finally ready to go back in.

I did end up pulling it apart, because on closer examination the teeth on the 1-2 and 3-4 slider things were just about gone. I bought myself a little press, replaced the 1,2,3 synchros and flipped the others. New dog teeth and slider things as mentioned, and the 3-4 fork was badly out of adjustment and very worn so I replaced it. Finally, a new Elring reseal kit and some K&W Coppercoat spray and M8 nuts and washers. This transmission was supposedly rebuilt when I got it a year ago, and the rest of the parts looked pretty good. I guess it's impossible to tell whether I caused all the wear or things were not replaced that should have been.

At least I've lost my fear of transmission work. It took a while, but after staring at it long enough, I figured out how the thing works. The biggest mental leap was understanding that each gear set is always engaged. Wow.

[rcecale]

Colin,

What's the latest? You said the 915 was ready to go back in, but have you installed it yet? Details, man, details!

Randy

[cowtown]

Hi Randy, I put it back in the day after I wrote that last update, and it's running fine. It shifts better than it did a year ago when I bought it. I think the shift forks were not set up correctly, because one fork was very worn, and some slider teeth were ground down, and it was just kind of hard to shift.

I've only put about 50 miles on it since reinstallation, but it seems much better now!