Is there a typical failure mode for losing 5th gear?

Y

ymz

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I know it's a silly question, but... (that's never stopped me before...)


When one loses 5th gear, is it usually something specific, such as stripping out of the splines in the gear shaft or actual gear or something breaking in the internal linkage to the shift fork, or... is each instance different? (I know I should take the cover off and have a look, but... I'm not sure what I'll be looking at... and as John Muir once said... to play with these you need to be in practice, and... I don't like to practice that much...



Y.
 
jokila

jokila

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When I had to work on a Beetle with a 5th gear failure it ended up being the shift fork pawls were worn.
 
oilhammer

oilhammer

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outside St Louis, MO
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There are just too many to list....
I would say it is a 50/50 split between the selector fork nubs (Volkswagen calls these a "shift segment") and the gears themselves. I have only seen a couple where the output shaft itself was damaged to the point it needed replacement.

And I still feel like, as always, the root cause for ANYTHING worn out in the 5th gear side housing area is from running the gearbox low on oil for too long, and it likely does not take much.

I always OVER fill the gearbox on these, by removing the roll mount bolts against the subframe and cranking the drivetrain UP in the front with a screw jack allowing me to squeeze another half liter of juice in. That way you know the 5th gear area has plenty of lubricant. You'd be amazed how many 02A/02J gearboxes I get in are a little low already. Gear oil seeps out a tiny bit over a long period of time, and doesn't necessarily make much of a mess and goes without notice, especially when we are talking cars that regularly pile up 300k+ miles like Volkswagens do.
 
Growler

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When 5th gear went out on Growler back in the day, my selector ring splines and the splined on the large 5th gear were what wore out. Failure mode was that it would pop out of gear and need to be held in 5th gear.

http://forums.tdiclub.com/showthread.php?t=126650&highlight=Beetle+pops Thread I started when it was happening.

The only way we could completely fix it was by replacing not only the 5th gear set, but also the large outer selector ring that moves to lock it into gear. My shift fork fingers were not worn out at all.

The car only had 74k on it when this happened. The car still has the .681 5th gear set in it now at 290k miles. My dad bought it back a year ago rom the guy I sold it to 13 years ago..
 
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AndyBees

AndyBees

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What Oilhammer said up there ^^^^^

And, here are a couple of pics from the tranny in my formerly owned 2000 Jetta at roughly 291k miles ...... with no obvious warning, just popped out of gear driving along about 45 mph. After that incident, it would not stay in gear for one second...

Worn hub below...


And below, obviously, from the looks of the pic below there was water contamination (too much pressure washing in the area of the vent on top of transmission:D) (Note: the oil was original, no obvious leaks but it was low, confirming Oilhammer's observations...)



Below, is a tranny at approximately 200k miles with no oil contamination ..


I installed a good used 5th gear set, flushed the tranny out by changing the oil about four or five times over about 5k miles with regular gear lube non-synthetic and then filled with OE spec oil. Almost 100k miles later, it shifts fine!
 
Matt-98AHU

Matt-98AHU

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3 failure modes, two of which I've seen repeatedly.

The first mode, which I haven't personally encountered yet but know people who have, teeth on the gear itself stripped off.

I have replaced a few transmissions for the splines on the output gear and shaft stripping, so the output gear just spins on the shaft, but the shaft doesn't get driven by the gear.

The last mode is what Growler and AndyBees have described. The symptoms are different, though. Where the above two failures the selector goes into gear and stays there, it just doesn't actually propel the car, whereas with the selector wear issue, it will pop out of gear when under load. The lever will literally pop right back to center the second you squeeze on the throttle. If you hold it into gear, it can actually temporarily work, but definitely not ideal. Replacing the selector and sometimes the gear itself are the fix there.
 
Y

ymz

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Thanks, guys... I'm still not sure I want to dive into the tranny - although I do have a used transmission (with a worn shifter tower) sitting around... the car has over 980,000 km... and my back isn't up to doing too much heavy mechanicing...


Y.
 
Y

ymz

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P2B said:
You are not allowed to park it at that mileage, might have to drive the next 20K in 4th ;)

Simon
Click to expand...
oh, it's being driven... (this just happened yesterday as my wife was driving to Montreal... I haven't seen the car since...)

Y.
 
AndyBees

AndyBees

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While looking for an OE 5th gear, I installed the 5th gear out of that nice clean gasser transmission in the pic above... I drove it that way for about 5k miles!:D
 
Matt-98AHU

Matt-98AHU

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AndyBees said:
While looking for an OE 5th gear, I installed the 5th gear out of that nice clean gasser transmission in the pic above... I drove it that way for about 5k miles!:D
Click to expand...
Was that like having two 4th gears? lol
 
Y

ymz

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Joined
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2003 Jetta TDI Wagon, 2003 Jetta TDI Wagon
Matt-98AHU said:
3 failure modes, two of which I've seen repeatedly.

The first mode, which I haven't personally encountered yet but know people who have, teeth on the gear itself stripped off.

I have replaced a few transmissions for the splines on the output gear and shaft stripping, so the output gear just spins on the shaft, but the shaft doesn't get driven by the gear.

The last mode is what Growler and AndyBees have described. The symptoms are different, though. Where the above two failures the selector goes into gear and stays there, it just doesn't actually propel the car, whereas with the selector wear issue, it will pop out of gear when under load. The lever will literally pop right back to center the second you squeeze on the throttle. If you hold it into gear, it can actually temporarily work, but definitely not ideal. Replacing the selector and sometimes the gear itself are the fix there.
Click to expand...
Well, the failure mode here is definitely not the 3rd... so... I guess the possibility's there that the splines on the gear and/or output shaft have stripped... which is not an easy repair... so... either we'll drive it in 4th or if my back recovers, perhaps I'll swap in that spare transmission I have - and try to swap over the shift tower... wish there was someone local who's familiar with tearing these units apart...



Yuri
 
turbocharged798

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oilhammer said:
I would say it is a 50/50 split between the selector fork nubs (Volkswagen calls these a "shift segment") and the gears themselves. I have only seen a couple where the output shaft itself was damaged to the point it needed replacement.

And I still feel like, as always, the root cause for ANYTHING worn out in the 5th gear side housing area is from running the gearbox low on oil for too long, and it likely does not take much.

I always OVER fill the gearbox on these, by removing the roll mount bolts against the subframe and cranking the drivetrain UP in the front with a screw jack allowing me to squeeze another half liter of juice in. That way you know the 5th gear area has plenty of lubricant. You'd be amazed how many 02A/02J gearboxes I get in are a little low already. Gear oil seeps out a tiny bit over a long period of time, and doesn't necessarily make much of a mess and goes without notice, especially when we are talking cars that regularly pile up 300k+ miles like Volkswagens do.
Click to expand...
I used to do that but found that the overfilled fluid would cause the trans to shift bad and fluid to turn dark quickly. Best I can figure its that its overworking the fluid and burning it up. I think the better practice is just to check your trans fluid on a regular basis like engine oil and keep it at the proper level.
 
jokila

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turbocharged798 said:
I used to do that but found that the overfilled fluid would cause the trans to shift bad and fluid to turn dark quickly. Best I can figure its that its overworking the fluid and burning it up. I think the better practice is just to check your trans fluid on a regular basis like engine oil and keep it at the proper level.
Click to expand...

My SOP is to change out gear oil every timing belt change unless leakage evident.
 
AndyBees

AndyBees

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Matt-98AHU said:
Was that like having two 4th gears? lol
Click to expand...
Matt, the ratio of the Gasser 5th gear is about half way between 4th and 5th in the TDI transmission. So, it was much better than driving around in 4th gear.:D

BTW, 4th gear in my Vanagon with the ALH is about the same as 4th gear in the TDI trans on the ground (consideration given for the R&P as well as tire size) ...... 3000 RPMs = about 70 mph.
 
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