Need help with drive line failure

[fbech]

Regarding my 1987 Tercel 4wd wagon, manual transmission with about 225,000 miles on it.

Was coasting with clutch disengaged down hill on gravel road so I could hear on cell phone. Coasted to a stop sign. When I tried to go nothing happened. The connection from engine to wheels is missing. Clutch pedal feels normal. Shifting transmission lever and 4wd lever feel normal. No connection in any gear or position of these levers. New clutch installed about 72,000 miles ago.

Anyone have any ideas about what failed or how to test to pinpoint the cause? I would like to minimize what I have to take apart to find and fix the problem. But, I need this car to get around as winter approaches.

I'll be grateful for any ideas.

[dlb]

first problem: talking on cell phone while driving. don't distract yourself from piloting the battering ram you have in your control.

first thing i would look at is CV's. if one of your CV's is completely blown apart and unable to turn its respective wheel, the other side will not work either. if that is the case you should be able to drive it in 4WD using just the rear wheels, and then replace the CV which isn't a big deal.

[Petros]

Welcome to the list!

Sorry to hear about your trouble. I do not see how CV would cause that, without any other symptoms. Could be a clutch failure, or an input shaft failure. Typically when there is an internal failure of the trans you get a lot of crunching noise. but occasionally if the shift linkage is worn it can pop our of engagement and the lever does nothing. I have seen clutch failures where the diaphragm spring breaks and than there is no pressure on the disk, so it just spins around.

Most likely you will have to drop the trans to determine if it is clutch or trans related, it has to come out anyway. But before you do that remove the center console, than remove (4) 10mm bolts that hold the lever boot, and than remove the cover over the shift linage and remove the lever It is tight clearance but it can be done to expose the shift linkage, if you have to you can unbolt the rear cross member and lower the trans). See if you can move the shift rods by hand to get it to engage, if it does, than you likely just need to replace the lever or some bushings. If that is a no go, than it is likely in the trans or clutch and it is time to pull the trans.

If the clutch failed, that is a fairly straightforward replacement. IF the main shaft on the trans failed, than that will be a much more involved and costly repair. You might have to find a replacement trans.

Good luck.

[dlb]

i had a CV completely fail on me in my FWD passat and it caused the exact same symptoms as fbech mentions: clutch and shifter feeling normal but no power to either of the wheels. i had a lot of clunking in the week building up to it, though. not sure why the other CV would not continue to turn its wheel, maybe someone here can explain that to me.

[Petros]

i had a CV completely fail on me in my FWD passat .... not sure why the other CV would not continue to turn its wheel, maybe someone here can explain that to me.

IT is called a differential. The design of the diff is intended to allow the wheels to turn at different speeds in a turn, but the effect is that power will go to the side with the least amount of traction. If you break one, it will spin freely and not allow the other axle to get any power since it has to pass through the spider gears. If you have 4wd (not AWD), the rear wheels will still drive you. So an quick way to check if it is a blown CV (which usually makes a lot of racket before it fails, and after too), is to put the Tercel in 4wd and see if it drives. If not it has to be in the clutch or input side of the trans.

see this: http://www.youtube.com/watch?v=K4JhruinbWc

or this: http://www.youtube.com/watch?v=gIGvhvOh ... re=related

[dlb]

ahhhhhh. i've seen that first video before but didn't think of how it could apply to my situation. makes sense now, thanks.

[splatterdog]

When coasting with the clutch pedal in, was the trans still in gear? And if so what gear? Big no-no if you were. Never seen it personally but I've read about coasting down hill blowing up clutches and it makes perfect sense. The lower gears are worse for this. What can happen is when the trans is in gear, clutch pedal in, coasting, it is being driven by the wheels. Motion from output going in makes the trans into a gear multiplier. This can spin the clutch at very high rpm's without the clamping force of the pressure plate to help hold it together against centrifugal force. Sometimes it can be violent and parts exit the bellhousing. You didn't mention any loud noises so yours may not have grenaded. You may have just lost the friction material which could be causing the problem.

If the pedal,cable, fork check out, not much to do but pull it apart I'm afraid.

I doubt it's bad CV's. No mention of horrible noises for a few months. The rarely give out without warning or different bad noises when the let go. Hopefully I'm wrong as that would be a lot easier.

[splatterdog]

Oops, double post.

[Petros]

one of my collage professors was a big car buff, when he was in collage he raced a Cunningham (2 seat sports car) in club slaloms. He described to me how he grenades the clutch when he over-reved to 12,000 rpm. He said there was only about 3 fragments of the bell housing left holding the trans to the engine. Lots of flying metal, much violence.

I have never seen it either, except when the material came off an oil soaked clutch. It did not take high rpm to cause that so nothing else was damaged and I just replaced the clutch disk.

[Petros]

One other thing, if you drop the trans and find the clutch oil damaged, you should replace the rear main seal and the trans input shaft seal while you are there replacing the clutch. It the input shaft is failed it can actually be replaced easy without having to pull the trans apart, you just pull off the access panel on the back of the bell housing and slip it out, install the replacement.

[dlb]

When coasting with the clutch pedal in, was the trans still in gear? And if so what gear? Big no-no if you were. Never seen it personally but I've read about coasting down hill blowing up clutches and it makes perfect sense. The lower gears are worse for this. What can happen is when the trans is in gear, clutch pedal in, coasting, it is being driven by the wheels. Motion from output going in makes the trans into a gear multiplier. This can spin the clutch at very high rpm's without the clamping force of the pressure plate to help hold it together against centrifugal force. Sometimes it can be violent and parts exit the bellhousing.

old thread revival. i've been messing around with some hypermiling lately but this particular post of SD's has been nagging at me. took me a while to find it again, wowee.

my question is: which method of coasting is safest for the clutch and trans? i understand the above explanation so i assume the shifter should always be in the neutral position when coasting, but should the clutch be engaged or disengaged? does it make much difference? it seems like when the clutch is engaged, it will spin the input shaft and its bearing, and when it is disengaged, the pilot and throwout bearings will spin. it seems like the pilot and throwout bearings are more prone to wearing out than the input shaft bearing but i'm not really sure. is this a case of six of one, half dozen of the other?

[marlinh]

I believe that if you are coasting you would want to be in neutral with your foot off the clutch. Like what was mentioned earlier the pressure plate holds the clutch in place and prevents catastrophic failure. The clutch is not designed to spin freely for long periods of time at high rpms. It is just meant to provide a convenient means of shifting gears. Otherwise, you have to match engine rpms and road speed (I believe) to shift without a clutch. Starting from a stop is the tricky one, but I've done it before when I have lost the linkage to the clutch whether it be hydraulic or mechanical.

[Petros]

I think you have it correct, the more immediate concern would be wearing out the T/O bearing and pilot bearing when holding the clutch down. You save the drag of the trans mainshaft, but put more wear on the T/O and pilot bearings. Consider however that the axles will turn the main shaft when costing anyway, the only savings is the little bit of extra drag from the other half of the main shaft that the engine has to turn when it is idling. So the savings if very minimal.

Put the trans in neutral when coasting. Keep your foot off the clutch as much as possible, and keep your hand off the shift lever, both will put wear on the clutch/trans parts, and will increase the drag slightly too.