My first torque converter failure

[Tim_K]

Here's a story about my first torque converter failure. Be prepared for some serious rambling here.

The car: 1971 Plymouth Valiant 4 door, my daily driver. 225, 904, 2.76 open 8-3/4" axle. 106,000 miles on the car and torque converter (stock converter), 33,000 on the 904, which had been rebuilt by someone else a few years before I got it - and sat unused 'till I put it in my car, and 165,000 on the 225, which came from an identical '72 Valiant 4 door I had owned prior to this one, but a 4 speed car.

The story: I had been using this car as the general daily driver. The 904 I had put in it had a nice shift kit and a 3.8 kickdown lever. It would bang the 1-2 shift pretty good. 2-3 was a little better than stock, but not as hard as 1-2. No, it didn't bark the tires on the 1-2 change. Maybe with a 360, but not a Slant Six. After 40,000 miles of abuse between me and my younger brother, who owned the car before me, the stock 7-1/4" rear was starting to go. Failing the left wheel bearing. That makes 5 7-1/4's behind /6's I've blown up one way or another. I had put in my A-body 8-3/4" axle 2 weeks before, with 3.23 gears. Soon after, changed them to 2.76's. The slant six was tach'ed up around 3,000 rpm to go about 65 mph, I needed more speed than this. And yes, the speedometer was right on. I'm the kind of person who thinks a 1% speedometer error is too much. I had thought the car responded to gear changes better with the 8-3/4", possibly due to it not flexing as much as the old 7-1/4 might have been.

The failure: So I'm leaving my friends house one night, right? Cruised down the alley to the main road, and hit the gas pretty good to squeal tire as I turned onto the main road. 15 minutes before South Park comes on TV, and 5 miles to go to get home. As I started up the hill, I had the gas pedal down about 80% to 90% of full throttle. The Slant Six wound up to about 3500 or so (wasn't watching the tach) and the 904 banged its 1-2 shift good and hard, just like always. And then...

About a quarter or half-second after the 1-2 shift (wasn't looking at my watch in the dark) there was some kind of dull BUMP noise down by the floor, in the general area of the transmission. Also a couple of sounds like metal moving around where it shouldn't be. The /6 was revving a little too high now, so I took my foot off the gas. Silence. Pressed the gas gently and heard sounds like fluid going around in the trans. (like when you pull it to manual low around 25 mph with the motor idling). Off and on the gas a couple times, worked the shifter from Neutral to Low, now even the fluid sounds are fading. The car is coasting uphill and slowing down fast, despite my best efforts to make it go. I'm gonna miss South Park if it doesn't fix itself immediately. I got it off to the side of the road as best I could, seeing as how there was this wall of rock in the way. Snapped on the 4-ways, and put the shifter in Park, which still worked. Got out with the flashlight, and looked underneath. No parts hanging out, no fluid dripping. The engine was still idling, and there were no unusual noises. While standing there thinking "WTF is going on here ?!?!?!" My friend and a neighbor pulled up behind me. They had been watching me go up the hill, as I had only made it about a quarter-mile from his house.

Now What? Well, we waited for all the Shivvys and Phords to get out of our way, then I put it in Neutral and coasted the car backwards down the hill, on the wrong side of the road. The other two were given the job of pushing my Mopar back down the alley to his house, while I drove (tough job, but someone's gotta do it). Rolled it into the back yard, his dad came out, then some other neighbors came over, so I had to tell the whole story about three times in ten minutes. Got a ride home from him. Missed South Park. Park and five Neutral positions. no drive in any gear. Period.

A few days later, I procured another 904 and changed it. Car runs ok, but since this other converter stalls at 1750 instead of 2000 like the old one, burnouts are history. Also since the replacement trans. upshifts at 4300 instead of 3800 like the old one, I'm losing 2 to 3 tenths in the quarter mile (now getting 18.9 to 19.2). Stupid transmission.

The diagnosis: My friend's dad insisted the pump was bad. I disagreed. I claimed mechanical failure, like stripping splines off the planetary gears or something. After tearing down the trans. and finding NOTHING wrong with it, (clean fluid, no metal shavings, no broken parts) I didn't know what to think, except his dad was crazy, It ran great to the last shift, COULDN'T have been the pump. Took apart the pump, just in case. Everything was good there, too. I called a few converter places, (B&M, Dynamic) and told them what happened. They didn't know, aside from a few guesses I'd already eliminated. Asked at a local trans. shop. Talked to their 'Chrysler guy'. He said check out the torque converter. Now, the two notches in the converter's drive tube both had a crack in their lower corner. One was broken far enough you could easily flex it with one finger. But that couldn't account for the sudden failure with no warning. Finally, checked the splines inside the torque converter. A-HAH!!! The splines that drive the input shaft were TOTALLY STRIPPED OFF inside! I could see where the splines were still good, way down in past where the input shaft splines engaged them. Rounded them off nice and smooth, just like that. Wow. Have never heard of that happening, even on drag race cars.

So the question is : Have any of you ever heard of this happening? Or had it happen yourself? I'm planning to build an all new 904 someday, and I'd like to avoid this if possible. I'm leaning towards Dynamic for a converter. B&M and GER are out of the question.

Well, there you have the story. Like I said, some serious rambling, right? I like getting into all the little details when describing a situation like this.

[Hoov]

I grenaded a converter the same way about 9 years ago in my 79 904 Volare. I had just left home when I heard it. I did an imediate 180 to get back home. I just made home and had to coast into the drive way. Nothing from the outside I could see. Anyway I removed the tranny the next day and took it to the shop and they said it was the converter. They recomended a tear down because of metal shavings making it to the rest of the tranny. 300 bucks and two days later, I was back on the road.

[DartGT66]

The craks in the pump drive is pretty common to the 904's. This will result in a front seal leak and afer that pump and front bearing failure. I have the same problem with my /6 904; it shifts to second gear at way too high rpm, the engine doesn't like to take that much rpm. And the shift is slow; I'll try to tighten the kickdown band 1/2 turns and see if that will help. Never run a full 1/4 with the slant six, but 1/8 mile time was 12.006 and the speed 60 mph. The start was very sluggish; the 360 converters stall speed was only 1300 rpm. Now with a 1800 stall converter I think it would ET a lot better.

[toolman]

Tim K I live for stories like the one you wrote! I just pulled this one up from the archives, and it's a doosey. What a crackup! Keep up the good work! Tim M. aka toolman ps. My girl says after reading over my shoulder "There isn't enough memory in there for the both of you."

[volare360]

i had a 79 aspen 318 904 and the converter locked, ie. like driving a standard with no clutch linkage.
That was interesting, rev engine, slam into gear.

[ChristianCuda]

I had a trans recently that had the rear clutches lock and weld together due to a bad drum. As soon as I installed it from the tranny shop it wanted to drive in Nuetral and Park just the parking brake kept it still. Not funny then but funny when you look at it I almost ran over my mom when I first started it up in nuetral revved it and the car lurched forward like in drive.

Drove it for awhile not realizing something was really wrong figured it was due to all the added stuff to the trans like the 5 disc front clutch added line pressure and B&M shift kit

i know now that i was wrong and should have had the trans rebuilt again. I did have it rebuilt recently and the guy even though it was over a year later rebuilt it for free but i had taken to him already out of the car.

Christian

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68 'Cuda 383 Working on adding EFI
69 'Cuda Race Parts Car
76 Duster 273 recent transplant
95 Neon 2.0 SOHC best of 16.96
84 Dodge Ram D50 transplanting 360

[Tim_K]

Toolman:
If you liked this story, do a search on my name and see some of the many, many (A little Commandant Lassard from Police Academy there) other topics I've written. "My first torque converter failure" was written less than a week after I found this place, and I've added a lot more wit and wisdom (A little Rush Limbaugh there) to this board since then. Try the articles "Speedometer Calibration" and "Sure-Grip rebuild" if nothing else. I'm glad I finally got a few more responses to this topic, seeing as how it took a lot of work to write properly. Gee, that only took five months, but I'm still happy to get input.

[Questions]

Tim

[Questions]

Tim K -

I always enjoy your "articles" - well written w/ a bit of humor and some good information. Thanks and keep them coming.

Ken

[toolman]

YA, I usually just see short quips or tech stuff, but when I came across this story I hit the jackpot. You should write for a Mopar Magazine! I can't wait to read your "other work". Thanks for the direction. And you definitly weren't rambling. By the way, which converter did you go with and how is it doing? I need one too, because the one I have is too loose, and I want to at least drive on the freeway once in a while. The one I have is from GER and out of principal(thier company sucks),I will never do business with them again. And if I am totally lucky, I won't ever have to do any warrantee work with them. Anyway I'll check you tomorrow, and thanks.

[Speedy#1]

Hay Tim that was a great story once again .I allway's got that feeling when i'm going about 35 and step on the gas the tranny shift's hard tires burning,ass end going sideways and BAM their go's anouther 71/4 set of spider gears so after about 4 rear end's i rip it out end and throw in a 81/4 rear end proublem salved ??? Now you gave me something else to worry about i guess i'll have to stay close to home when i do that .Can't you use a stall converter out of a stock 360 ,will that give you more stall speed real cheep? Not sure if it will bolt up i'll look it up tonight and see what i can find out.