'03 Automatic Transmission Shudder and Other Qs

Sorry for the open-ended question that follows, but I am not very knowledgeable about A/Ts in general, nor Tacomas. But I'm comfortable working on most things and I'm a quick learner.

Vehicle: 2003 Tacoma, 4WD, 2.7L, A/T. About 200k miles. I bought this used (private sale) and it didn't do the shudder on the test drive. Lucky me, it started doing it after I paid cash and started the long drive home. I have no maintenance history on the vehicle.

Symptom: Occasionally shudders under light load in top gear. If I'm cruising and 55 and begin up an incline, at times it will shudder (maybe 1/3 of the time). The same thing can happen if I gently increase the accelerator while cruising in top gear. However if I give it some gas to force it to down shift, it never shudders in lower gears at any load. There are no transmission dash warning lights or codes that I can tell. It works flawlessly otherwise.

Clarifications needed: what gear is top gear? As I count it, this A/T has five "gears". I believe the transmission is a 340E or 340F. I'm not sure how to tell which. Is the top (fifth) "gear" a torque converter lock-up mechanism? If so that is where the problem is manifesting. As I said it works perfectly.

I found this great high-level thread:
https://www.tacomaworld.com/threads...sions-write-up-your-4-speed-automatic.325531/

But I'm too new to the subject matter to make a lot of progress.

Last bit of clarifying info: I checked the A/T fluid level (hot, while running) and it's overfull. So I assume I'm going to have to drain fluid.

Last question: I dislike A/Ts immensely. But I wanted the 2.7L 4WD and this was the only worthwhile one, so I bought it. If the A/T dies at some point in the future is it possible to bolt the 2003 Tacoma manual transmission into this pickup? The 2.7s did come with manual transmissions...

 

Hey Hoopy. Not to divert from the transmission, but I had a very similar issue on my '03 3.4 automatic. I realize yours is a 4 cyl so it could be totally different. My truck was shuttering like what you mentioned above, and I would have bet my life on it that it was the transmission. No check engine light either. Took it to the dealer and it turned out to be a cracked spark plug.
Again, just a thought since you may not know the history of this one.
Good luck

 

Wow, really? You'd think a spark plug issue would show up in any gear. Or at least I would, but I've been known to be wrong Easy enough to take a look at 'em. Thanks!

 

I agree with you. Was only bucking and shuttering when going up an incline.

 

Gently tapping the brake pedal when you feel the vibration will tell you if your issue is a torque converter problem or an engine misfire problem .
Take the truck for a drive , wait for the shuddering / vibration to start . Gently tap the brake pedal with your left foot but keep your right foot on the gas pedal maintaining your speed . You are not actually hitting the brakes ,you are manipulating the brake switch under the brake pedal . Did the vibration go away for a couple seconds ?
By switching the brake switch with your foot , you are essentially turning the torque converter clutch on and off

The A340 series transmission is a 4 speed with converter lock up . The converter lock up makes it feel like you have a 5th gear.
When you are driving at highway speeds , the transmission will shift from 3rd gear ( direct drive ) into (overdrive )4th gear .
Now that the truck has shifted into 4th gear , the computer commands the torque converter clutch to lock basically locking your engine power directly to the transmission . With the engine locked directly to the trans , bad spark plugs will make the truck shudder . When was you last tune up ?

If its time for spark plugs , might as well do your throttle body as well
How to for 2.7 http://www.tacomaworld.com/forum/1s...o-throttle-body-intake-manifold-cleaning.html

Transmission swap thread https://www.tacomaworld.com/threads/transmission-swap-write-up-s.384303/

 

Gearcruncher, that is amazing! I will conduct this test as soon as I can. Once I've diagnosed one way or the other I'll post and update with any interesting additional info.

And thank you so much for the links! I have a lot of homework to do

 

I have 2.7L AT

Mine is 4 speed automatic. Not 5 speed.

There is no shudder in mine. Only axle wrap at lights.