Transmission loosing Teeth??

[nene]

Well, after having my 1986 Carrera for a little more than a year, I decided to change the transmission oil with Kendal 80-90.

After battling with the fill/drain plugs, I left the oil drain for about 10 minutes or so, which I was surprised that that's all it took. And yes the car was on level ground. I also noticed that when fully drained that their was not 3 quarts of oil in the container

Anyway, I was very interested in seeing if anything showed up on the magnetic part of the drain plug, which there was..........and it had "Teeth" Note, the engine and tranny had been rebuilt by the PO at some point, of course no docs to prove it.

Now, the question is, is it ok running the car like this?

The tranny runs fine with no odd issues. I did notice a slight improvement when shifting gears, but again the tranny runs fairly well.

[Steve@Rennsport]

Not good.

Thats a piece of operating sleeve (slider) which engages the coupling teeth on the gearset.

I'd be very concerned about the rest of the OS coming apart and causing serious damage.

If it were my car, I would take the transmission apart for a thorough inspection.

[nene]

Thank you Steve.

Serge

[Walt Fricke]

Worse - it looks to be from the toothed part which is pressed into the gear.

You can see these teeth on two gears, with the slider which goes back and forth and engages one gear or the other. The slider is kind of hidden behind the brass part (which is what moves the slider back and forth), and the slider is in the neutral position, not engaged with either gear.



You can see that these engagement teeth stick out a fair amount, so are more subject to breaking off (though I've not done that, I've just worn the teeth down to nubs which don't work well).

The slider teeth are much more strongly supported, being cut into a ring rather than sticking out, and their problem is wear.

With a broken engagement tooth, the whole assembly is apt to break sooner rather than later, as in the picture below. This releases the synchro band, as well as the giant circlip-like piece which holds things in place, and some hard parts inside which would really do a number on your whole transmission - like bend shafts and crack the case - if they got into the mesh of two gears.



Steve is being his usual polite and diplomatic self when he suggests inspection. I wouldn't drive another mile on that box. All the torque of the engine passes through those teeth. You can probably do with one less tooth, but, from the looks of it, it wasn't just the tip which broke off. It broke back into the machined ring part, which means that was weakened.

It is just possible that this tooth is from a previous disaster, before the rebuild, and somehow wasn't cleaned out. That doesn't seem likely - who would ignore this sitting in the magnetic plug? And when you take the transmission case parts off there really isn't anywhere for something of this size to hide. But it could be.

A shop with a borescope might be able, by draining the oil and removing the plate on the bottom which is held on with four bolts, to inspect each of the four engagement teeth inside the transmission without taking it out and disassembling it to see if any teeth are missing.

However, 5th gear has similar teeth, and I can't think of how you could get a borescope into that compartment short of having the kind of equipment the surgeons use and can manipulate (and even that would be iffy). But I have never tried.

[Spenny_b]

Hi Walt, Steve,

Thankfully I have no transmission worries, just a curiosity, as I've never stripped a gearbox before....with the scenario here, what do you guys reckon the OP's exposure is financially, to open the box for a look/see?....Is it pretty straightforward to unbolt the various sections of the housing? Just a case of replacing a few gaskets and the oil, if there aren't any obvious problems?

For a quick inspection, are any specialist tools required to dismantle?

Cheers
Spencer

[Matt Monson]

$2500, parts and labor, do do it right. Lots of pms sent behind the scenes here with R&S b grade synchros and sliders sold at 80 cents on the dollar and discounted labor on top of it.
The days of a cheap 915 rebuild are over. Still guys offering them but their 12 month warranty is worth about 13 months.
You want a 5-10 year box? Pay Steve or someone similar to remanufacture (not "rebuild") it short term. Too many IB cars got cheapo rebuilds over the last 10 years.

[DSPTurtle]

Opening the box to do an inspection on the synchros is pretty straight forward. You will need a decent impact gun to zip off the big nut but other than that I've never needed anything "special" to replace synchros.

[nene]

Great dialogue here, but getting even more confused.

Serge

[nene]

Well, I have had the car for more than a year and have put over a thousand miles on it, wouldn't it stand to reason that the syncro would have broken by now (just my thinking)?

So, if I understand it correctly, once I drain the tranny oil and remove the bottom plate with the four bolts, the gears are visible from there?

Serge

[MetalDoc]

To do an inspection I don't think you'll be able to drop the plate and look inside. I think you'll need to drop the transmission and take off the housings to see everything.

[Steve@Rennsport]

Originally Posted by nene

Well, I have had the car for more than a year and have put over a thousand miles on it, wouldn't it stand to reason that the syncro would have broken by now (just my thinking)?

So, if I understand it correctly, once I drain the tranny oil and remove the bottom plate with the four bolts, the gears are visible from there?

Serge

Hi Serge,

The only way to inspect these transmissions is by removing the end cover and the gear case from the differential case and disassembling everything.

Only then, will you really know what you have and what parts will be required to rebuild it properly.

[Matt Monson]

What Steve said.
You can get a general idea of overall condition by pulling the plate on the bottom and by removing the CVs and pulling the sidecover off. Then you can inspect the differential and ring and pinion assembly.
But when you find loose teeth they ALWAYS need to be stripped and replaced. Eventually more teeth break, the synchro peels off and then you've got a $5000 rebuild on your hand.

Are you feeling lucky?

[VFR750]

Having broken a transmission in the past year, I can speak with relevant advice.

It is not if, it is when, you will hurry a shift and destroy the insides.

I too drained the box in the spring of 2013. Put fresh swepco 201 in it. No evidence of broken teeth.

Fall 2013, casual drive to work. Synchro band came off and I trashed the box.

All are trying to say: you are lucky. You are seeing the first stages of transmission failure. You should get it properly repaired now, when it is not broken. If you wait and break it, it will cost a lot more to make right. And you will likely be stranded when it does break.

It kinda sucks to be into the car for only one year, and now this. I understand that. This just one of those things.