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Transmission Shudder and How to Fix It

The Scenario:

You are cruising along somewhere between 40 and 60 MPH and all of a sudden you feel you car or truck shake badly. It feels like you ran over rumble strips, a washboard, or those divots on the side of the highway. The feeling only lasts two to three seconds and it definitely got your attention. You consider what just happened and you know there were no rumble strips or a washboard in the road and you were definitely in your lane. What could that shaking have been?

Torque converter shudder, that is what.

Crap. How much is this going to cost?

The Reality:

To paraphrase a plumber on a 1990’s sitcom: “It may cost you a little, it may cost you a lot, but it will cost you.

Let us consider what is going on before we jump to conclusions.

A torque converter is a mechanical device that is driven by hydraulic fluid. It is found only in vehicles with an automatic transmission. The converter transfers the power from the engine to the transmission. The shudder occurs when the transmission fluid can no longer perform or when the converter fails mechanically. There may be a mechanical issue or a fluid issue. Consequently, one may lead to the other.

Considering what causes the failure will determine how much it will take to repair the vehicle.

Start with a change of the transmission fluid. This is the easiest and cheapest method. Not necessarily the cleanest. Changing the transmission fluid can be a messy job. The ENTIRE amount of fluid must be drained from the transmission pan AND torque converter. This is hugely important. The torque converter holds about 30%-50% of the fluid that goes into the trans. If this is not drained, or as on some models not serviceable i.e. no drain plug, changing the fluid and screen by taking the pan off is a waste of time, especially if done more than once. Change the transmission screen while you have the pan removed if you can drain the torque converter for a complete service.

If the torque converter cannot be drained, you may need to try a transmission flush at a repair shop. The flush pushes the old fluid out with the new fluid and actually does a decent job of it. I have used BG and MOC brand machines. They are easy to use and perform well. The last I heard a transmission flush was in the range of $100-$120. You may find coupons for this service in the local VAL-PAK or Sunday paper. Be aware that the shop may want to sell you an additive packet, usually there is a flushing chemical and then an additive that goes in after the flush. I have no evidence that these chemicals help. Snake oil? You decide. Just be ready for that pitch if the situation arises.

It’s flushed. Now What?

You will need to drive your vehicle as you normally would after you have the fluid and screen replaced. Remember, the flush was the cheapest and easiest attempt. The shudder may not be eliminated.

If the shudder is still present you will most likely need to replace your torque converter. For that, I would recommend a professional. If you have considerable mechanical experience, read on…

I would say the job is not always easy to do and may be completed in the driveway–with the right tools and help. Sound scary? If you have never done it you should be scared. It is a big job. The transmission is VERY heavy and would require the use of a jack and maybe another set of hands to remove. Moreover, replacing the torque converter is more about physical labor than mechanical technicalities. This is the point at which you should consider the time vs. money situation.

To sum up:

  • If you cannot drain the torque converter, try a complete transmission flush at a repair shop.
  • If you did drain both the pan and torque converter already or previously flushed the transmission and still feel the shudder, you most likely need to replace the torque converter. Changing all the fluid again is a long shot.
  • If you changed the fluid and the screen but did not drain the torque converter, find out if it has a drain plug. If it does change ALL the fluid and screen again.
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