Genia and Mike's Walmart Frolic Gone Wrong

[MikeyP]

So there we were on our way to the nearby Walmart store in West Lafayette, Indiana. After searching through the store for some specific items, we proceeded to head to the mall. As we got into the van, we were cracking jokes and having a good time. Genia shifts into reverse.

The van struggles for a second, and I can feel the clutch moving slightly in and slightly out of gear as she give it gas. Shortly following the application of gas, I can hear a steel tooth from the reverse gear get sheared off. Instantly thinking 'oh crap!', I tell her to put the van into park, and then slowly put it into reverse again and slowly release the brake. (I was hoping we could at least back out of the parking spot half way because we were boxed in.) Immediately, in about 2 seconds, I heard ever single tooth on the reverse gear get sheared off and the engine rev up. So, reverse gear is dead.

We got lucky at that time. As we had the van in park and were discussing the options, a family that parked in front of us was leaving. Good, we can drive out of here possibly and make it to an open area to call a tow truck. Genia then put the van into drive very slowly and slowly released the brake and let the clutch pull the van out of the parking spot and turn left, to leave the parking lot. The transmission made it a heroic 50 feet before, in one swift action, every tooth on the transmission was sheared off by the other teeth inside. So there we were, stuck in front of the store that has everything, except new transmissions and a garage. We then had to call her parents to give me a ride back to my dorm and call leave her dad to call a tow truck.

So, I basically got about half an hour or so to hang out with Genia and plot the next plan to take over the world whilst the van sat back and died peacefully after an inspirational fight to make it out of the Walmart parking lot.

[Eugenia Gabrielov]

Man. My car breaks down, and the first people we tell is Chief.

I'd like to thank Mike publicly and profusely for not freaking out when I started to do so. Had it not been for the guy's knowledge of cars and gears and other stuff I would just kinda panickified.

And to think, all I wanted was some brownies...and shoes...but that's for another time.

Any comments guys?

And does anybody wanna explain the whole "clutch" vs "transmission" concept to me while we're discussing it?

- Genia

[Jay H 237]

Sounds like one of the Chrysler minivans to me.

[Eugenia Gabrielov]

It's actaully a 2-wheel drive 1996 Dodge Caravan. We had the transmission fixed a few months ago and paid a pretty penny for it, so I'm very sad that it broke down again.

[dubious elise]

Aha, frolic-ing with Genia I see!
Not that I can really help you in the car department, but I must say, you aren't alone on this one. Thankfully, I don't drive stick, but if I did, I would have done the exact same thing!

In the mean time, I know of one sweet, magenta, two-door, automatic '96 Dodge Neon that you could take off of my hands

[Pat McCarthy]

I am quite nearly speechless (good thing I'm typing)

Yeah, I'd probably end up doing something like that if I had a manual tranny too! Will the van be getting repaired or will it be junked?

[Eugenia Gabrielov]

It's automatic...but I thinik it's 2 wheel-drive...no...maybe it's front-wheel drive...god I'm so confused.

I don't understand my car, and I don't know what we're gonna do wtih it now.

[Pat McCarthy]

Originally Posted by Eugenia Gabrielov

It's automatic...but I thinik it's 2 wheel-drive...no...maybe it's front-wheel drive...god I'm so confused.

I don't understand my car, and I don't know what we're gonna do wtih it now.

Wait! Automatics don't have clutches. (that i know of) how's that work? Please explain the initial conditions and shifts in more detail.
Hey, I'm the engineering type, I'm interested if it was material defectiveness, or someone not using it in the correct manner.

[Eugenia Gabrielov]

I wasn't sure if there was a problem when I was driving around before hand, so I was careful with it. I put on the brakes to shift gears, and Mike and I heard a really wierd sound, which he later described as the reverse gear teeth being sheared. I dunno what that means, but it makes sense. So I oh so slowly put it back in park and tried again, and then it died. With much aplomb.

We then shifted into Drive, praying that it would go forward. I made a wide turn nearing the front of the parking lot, and slow as it was, that amount of torque seemed just enough to let the dead teeth kill the other teeth.

And that's what happened as interpreted.

Usage wise, we haven't had this problem before, not when I've driven at least, so it seems to be either a structural or material defect. Maybe I'm wrong.

Edit: To clarify, I was never moving while shifting the gear thingy by the steering wheel.

- Genia

[MikeyP]

automatics do have clutches. they are actually clutch packs, that work just like the clutch in a manual transmission car, except they are controlled by passages in the transmission itself. refer to http://auto.howstuffworks.com/automa...smission11.htm for more info.

Mike

[Tristan Lall]

Originally Posted by Jay H 237

Sounds like one of the Chrysler minivans to me.

The early-1990s Chrysler (and family) automatics tended to fail with regularity, but this deficiency has supposedly been corrected in later models. (So I hope...I had a '92 with no transmission issues over nine years, and the '00 seems to be holding up so far--it's got the heavy-duty transmission cooler, which can only help matters.)

Many of those problems were, however, attributable to the use of the wrong transmission fluid, or not draining and refilling fluid occasionally, or not replacing the transmission fluid filter. Your first step should be to figure out if any of those things were changed when the transmission was serviced. Did the shop use Dexron fluid? If they did, you might consider blaming them. The transmission needs ATF+3, and has been widely reported to die horribly if it isn't supplied.

As for the automatic vs. manual thing, the "P" position is a giveaway (the manual wouldn't have it), as is the "slowly released the brake" portion of the anecdote (manuals don't creep like automatics, thanks to their lack of a torque converter). But the clutch packs in an automatic (which engage gearsets, rather than the engine output) work a little differently than you might suspect; they basically lock planetaries together to change the gear ratio at the driveshaft (or in this case, the front axle).

By the way, Eugenia, FWD is 2WD, which is what you've got. You'd easily be able to tell if it were an AWD version by the decals on the tailgate (in addition to the obvious mechanical differences, like a driveshaft sprouting from the transaxle, or the smaller gas tank).

Edit: I just realized, you could also have a 3-speed, in which case, some of this may not apply; all my experience is with the 4-speed automatic.

[Pat McCarthy]

Originally Posted by MikeFrom71

automatics do have clutches. they are actually clutch packs, that work just like the clutch in a manual transmission car, except they are controlled by passages in the transmission itself. refer to http://auto.howstuffworks.com/automa...smission11.htm for more info.

Mike

Yeah, I didn't really know all that much about car tranny's to this point. Just the very basics. Thanks! *Rep*

[tkwetzel]

Here goes some of my hard-earned (and expensive) education (I took two transmission classes last semester):

Tristan has given the best and most complete answer so far. Clutch packs are used to lock planetary gears which control the output ratio and rotational direction of the tranny. There are also bands in the transmission that have more control than the clutch packs (there are usually 3-4 bands and 1-2 clutch packs in a 3 or 4 speed automatic). The bands wrap around a large drum that is connected to part of the planetary set. The bands are tightened to lock a certain drum and therefore lock a certain gear in the planetary.

I would highly doubt that the gears in a automatic sheered off. The bands and clutches should slip before the integrity of a gear is compromised. And there is not much room inside the tranny, especially where the planetaries are, so if one tooth breaks, it doesn't have room to move and would affect the other teeth greatly.

There is no reverse gear in an automatic transmission. Reverse is achieved by locking one of the planetaries in a way such that it reverses the direction of rotation (usually locking a sun gear). The movement is transferred through multiple planetaries in most automatic transmissions until it reaches the higher gears. The same planetary set used for reverse would also be used for first gear and would affect the driving accordingly.

From what was described, I would guess that your problem is in the differential and not the transmission, but it could be either. The differential on FWD cars is technically part of the transmission, but acts separately.

If anything I said didn't make sense, feel free to ask questions.

[KenWittlief]

Oh man I cant believe you fell for that one

"The car wont go- guess were stuck here"

"oH no - were out of gas......"

"I think the flux capacitor is clogged"

or back 150 years ago, "sorry dear, the horse has come down with a bad case of the jitters, we better stop here for a while"

:^)

[sanddrag]

If the van is FWD then there is no transfer case. Have you tried putting it in 2nd and driving it?