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Can a lockup torque converter causd rumble/vibration?

This us a follow-up to my previous post about an '89 Dodge B250 with a rumble/vibration problem that begins at 40 mph and grows steadily worse with speed. The strangr thing is, it depends totally on engine load. When I lift off the gas at highway speed, the rumble/vibe instantly disappears. Get back on the gas, and it immediately reappears.

The reason for this new posting is that I just found the owners manual and read it. The manual says “some models” have a lockup torque converter with an electronic clutch that kicks in at 40 mph under light load…which is the exact conditn where I started hearing/feeling the vibe rumble. And if I interpret the manual correctly, it means the lockup disengages when the load is released…exactly what happens when I lift off the gas and the rumble/vibe disappears.

So the question is, could it possibly be a problem with the lockup torque converter? I’m hoping a tranny expert like transman will tell me no, because obviously I’d rather have it be some bad U- joints. But it seems beyond coincidental that the symptoms appear exactly when the lockup ( if it’s in there) should be kicking in.

By the way, it’s an A500 trans, if that helps.

Yes. Torque convertor shudder often occurs at 40 to 45 MPH when the torque convertor clutch is failing. Proper fluid is required for smooth torque convertor engagement but if the pronblem is that severe new fluid isn’t going to help.

When the vibration occurs maitain the same throttle position but apply the brake pedal just enough to turn on the brake lights. This will send a signal to the PCM to disengage the torque convertor lock up. See if this has an effect.

Dadgum it! What’s a new/ rebuilt torque converter clutch going to cost me?

PS–thanks for the tip about brake disengagement. I’ll try that.

And here’s another question…since the lockup is electrically activated, could I just disconnect the wires that power the lockup mechanism and call it a day? I’m not going to be driving this thing much except for a few road trips this summer, and the fuel economy probably is already bad, so getting a 10% improvement in hwy mpg from the lockup mechanism isn’t going to do me much good…if I save a grand by not fixing the lockup, that’s an extra 250 gallons of gas I can afford to buy instead, for at least 2500-3000 miles of driving, and there’s no way in heck that fixing this lockup is going to save me anywhere near 250 gallons of gas.

So can I just unplug the lockup and call it good enough?

Disconnecting the torque convertor solenoid would be asking for trouble. An unlocked torque convertor generates heat and an already failing torque convertor clutch may one day come apart when it is inconvenient.

IF you don’t replace it in time the valve body will become plugged with torque convertor clutch material and the transmission won’t engage anymore. If you can do it yourself, a reman. torque convertor seals, filter and fluid, about $200.

Is there any chance a drain/fill, or flush, with the correct fluid might solve it? I’d be willing to spend $100 if there was some possibility it could avert a $500 rebuild, say. (Not something I want to attempt myself, so I’m going to have to pay for labor, too.)

I just read on a Dodge forum where a guy with an A500 had the same symptoms, and he said it was caused by previous owner using Dexron instead of ATF +4.

““And if I interpret the manual correctly, it means the lockup disengages when the load is released…exactly what happens when I lift off the gas and the rumble/vibe disappears.””

I don’t think you interptet the manual correctly. The lockup doesn’t disengage when the load is released.
Did you make sure that the muffler/exhaust system was not making the sound/feel that you experience?

You might try adding this http://www.midwayautosupply.com/p-12145-lubegard-dr-trannys-instant-shudder-fixx-2-oz-19610.aspx to the tranny fluid to see if it gets rid of the TCC shudder.

Tester

Elly, yes, definitely not muffler/exhaust. I can rev the engine in park or in lower gears/speeds, and there’s no hint of the problem. If it were exhaust/muffler related, I should be able to reproduce it just by revving the engine, and I can’t.

I will try Nevada’s suggestion to tap the brakes and see if that disengages the lockup and makes the shudder go away.

It is possible that replacing the fluid may help but if you are experiencing a continous shudder not just a shudder on initial engagement I’m not optimistic about the results.

Tester, you may just have saved my very expensive bacon. Never heard of the Dr Tranny’s Instant Shudder Fix, but I just read 22 reviews of the stuff on Amazon, and 21 of those raved about it. Only one guy said it didn’t work for him. I buy a lot of stuff from Amazon and have found that reading a bunch of reviews gives me a pretty accurate idea of the product…so if 95% of the reviewers are raving about it and saying it was the best $8 auto repair they ever bought, you bet I’m going to plunk down my $8.

Tester, if this works, I’d buy you a steak dinner if I knew how to mail it to you…

It won’t cost mush to remove the transmission pan and check for exessive debris. If it looks ok at least you’ll have 4 new quarts of fluid and a filter in it when finished.

Nevada, yes, I will have the pan dropped and the filter and fluid changed too, thanks.

Well, that’s strange…I took the van in for a state inspection ths morning, and on the way there I tried Nevada’s method of tapping the brake to disengage the lockup…but the shudder has almost completely disappeared. There’s just a little drivetrain vibration now that’s probably a bad tire or slightly worn U-joint, but it’s nothing like the horrendous shuddering that I got when I first drove the van home after buying it.

I’m convinced it was TCC shudder; the mystery is why it suddenly disappeared. The van hadn’t been driven on the highway for at least a year, maybe longer, before I bought it. So perhaps the lockup clutch wasn’t working quite right from lack of exercise, and it took some driving to get it working again.

Anyway, the good news is I won’t need a TC rebuild. Thanks for all the suggestions, especially the Dr Tranny additive. I’m still going to throw that in, just to see what happens.

And here’s another question…since the lockup is electrically activated, could I just disconnect the wires that power the lockup mechanism and call it a day? I’m not going to be driving this thing much except for a few road trips this summer, and the fuel economy probably is already bad, so getting a 10% improvement in hwy mpg from the lockup mechanism isn’t going to do me much good

Let me relate my personal experience in the event your shudder re-appears. I bought a well used '88 K2500 that had experienced severe tranny abuse. Best I could ascertain, it had done duty on farms in Kansas. The doors had those giant trailer mirrors and were full of dirt dust I discovered when I had to fix one of the window regulators, the bumper was all bent out of shape from the hitch they used and it had the big helper springs and stops on the back. This thing lived a tough first life on a farm.

The fluid was nasty brown color, the TC had similar shudder to yours. Looking for a beater truck to do some hauling/plowing I didn’t invest much and didn’t care if it died and I had to put in a rebuilt transmission some day. I replaced the fluid and disconnected the TCC connector. I had heard all kinds of dire predictions about heat related failures due to no lockup function but figured I’d run auto trannies many years prior to lockups, we’d see what happened.

In short, that truck ran like that for the better part of 8 years before I basically gave it away (it was still going strong). I plowed, towed boats and trailers all over the place. It saw harsh duty. Three years before I got rid of it, it hauled over 8,000 lbs of trailer and gear from WI to MA in one trip!

Thanks, Turbo, good to hear some personal experience on the subject. I am curious to see how this Dr Tranny stuff would work if the shudder comes back…but if all else fails, I’ll just pull the plug like you did…

Remember, that stuff is just a band aid. If it works, great but dont EXPECT it to work. DO NOT disconnect the converter clutch. The transmission will run hotter and will overheat. You either have a trashed converter or a little too much wear in the valve body, or both.

transman

Transman, is it plausible that this WAS a TCC shudder problem caused by lack of highway driving for a year or more, and that driving at highway speeds eventually got the clutch working properly again?

Twin-Turbo just said that he disconnected the TTC and drove it 8 years longer. If you drive around town all day, the tcc doesn’t lockup any way and that doesn’t seem to burn up a transmission. I would not be afraid to try it.

jesmed, you said …I took the van in for a state inspection ths morning, and on the way there I tried Nevada’s method of tapping the brake to disengage the lockup…but the shudder has almost completely disappeared.
I have had experience with a '94 Dodge 1500, a '96 B-2500, and a '99 Durango and tapping the brake petal does not release the TCC. Now it did in my '99 and 2001 S-10.