Clunk on brake release, and excess downshifting

[Climber76]

I have a nearly new 2009 double cab 4x4, automatic transmission, towing package. It has two quirks I don't like, and I was wondering if others had the same issues and/or if these indicate problems.

First, when I release the brakes, there is a clunking sound from the rear. Sometimes the clunk only happens on initial acceleration, not at the moment I release the brakes. It seems to happen mainly when I have stopped fairly quickly or on a downgrade. I suspect that what I'm hearing is the overload springs fetching up on the longer leaf springs as the axle shifts with torque. But seems like it shouldn't do that. Any other ideas of what could cause this? I have not had any of the other transmission/drive line issues others have described, other than that the transmission occasionally goes into lockup mode a bit harshly after I accelerate onto the freeway.

Second, when I go around corners around town, or go over a large speed bump, the transmission downshifts two gears and the engine races for a second when I begin to accelerate again. I'm driving very gently, trying to get the best mileage I can, so the transmission isn't responding to actual load. It seems to be anticipating a load that isn't there. Seems completely unnecessary and is very irritating. Is this normal? Dealer says yes, but I'm wondering if there's either a problem with an accelerometer, or a programming issue.

Otherwise I like the truck, though fuel economy could be better (getting 17 mpg average in Albuquerque in-town mix of freeway and street driving).

Thanks for any insights.

[Climber76]

Replying to my own post, got some info off the Tacoma world forum. Folks there are describing the downshifting issue as "transmission lag," and lots of people are complaining about it specifically with regard to the 2009s. They seem to have messed with the programming and quite a few people are unhappy with it. I'd like to see a fix for this.

The clunk or thud seems to fit symptoms others are attributing to axle wrap, thanks to the flimsy springs.

I'm gonna complain about both issues with the dealer, just to get it on record. I'll report back if they have anything helpful.

[Splicer]

I have not heard of either issue. It'll be interesting to hear what you learn about them.

[ffrda]

I have a 2009 double cab Tacoma and I have been experiencing the EXACT same problem.....there is a definite "lag" when I turn a corner, my engine races, and I have been wondering why.....glad to hear it's not just my truck, but look forward to hearing what Toyota says about it.

[05Moose]

Originally Posted by Splicer

I have not heard of either issue. It'll be interesting to hear what you learn about them.

People have been complaining about the axle wrap for years. Most say it was decreased when getting the TSB done. Others in the past installed helper springs backwards to reduce the axle wrap (Sharing the Wealth- Traction Mod - Toyota Forums :: Toyota Nation).

And yes there are a lot of complaints beginning with the '09s about acceleration lag (like what we experience on the highlander...major lag there!).

[Splicer]

Guess I was not paying close enough attention I have heard complaints of axle wrap but didn't make the connection by his posting of a clunk... and I have apparently totally missed the acceleration lag issue, probably didn't read the posts because it didn't concern me. I don't read 'em all, y'know...

[agjr200hp]

I have a 2006 Tacoma. i have had my truck in 3 or 4 times for a "clunk" when I hit the brakes. they are calling it "pad slap" and say it is coming from the front. Basically, the first time i hit the brakes in one direction, it makes the noise. When I switch directions, it does it again in that direction. It has been getting progressively worse since about 30,000 miles. I now have almost 40,000.

I would love to know what this TSB is and if you think it sounds like the same issue.

Thx.

[tammikm]

mine does the pad slap aswell, toyota told me it was normal, they said they could grease them but it will only come back after a bit, as the pads are a floating design.

[Jason.MZW20]

Might be the new transmission AI system causing the pre-emptive downshifts. You'll have to teach it some manners I suspect.

The 4-leaf springs will help the axle wrap a bit. It'll go away for a while, then when the new springs settle, it will come back, but it won't be as severe.

[dfense]

Glad to hear that the transmission problem is not just mine I will complain to the dealer to get on record.