Hey guys,

I drove my Dak about 160 miles yesterday. I noticed something weird was happening though. I'd be cruising at like 70 mph (which is as quick as it'll go in it's final gear without downshifting) and sitting around 2200 rpm's and the rpm's would randomly drop to like 1800 about 5 or so minutes after. It was as if the transmission hadn't fully shifted into overdrive and it did this the whole way so it was definitely not that it was cold. So after it did that I'd be going like 70 mph at 1800 rpm and it would randomly kick the rpms back up to 2200 like it came back out of overdrive. And this was with no hills or anything. It had no reason to downshift. Any ideas what's going on?

It's got fresh fluid and a new filter and all else seems fine, it's just this weird little thing. I'd like to figure this out before I really screw something up... I'm at 143,000 on the original transmission, so I know I may be on borrowed time, but I don't have time or money to put a trans in it right now. Any help is appreciated. Thanks

 

If you were cruising at 2200, OD would drop it to ~1600 once the torque convertor locked up.

And oh by the way, I think it's the torque convertor unlocking. Which, is not exactly a good thing. Mine filled the entire trans with clutch dust and seized up all the solenoids. It could also be going into/out of OD with the TCC unlocked, which is not legal in the PCM, but could still happen by some fluke issue.

 

Yeah, it would only drop down to 1800, so maybe it wasn't even fully going into OD? I dunno, something is going on and I don't like it. Could it be a bad solenoid that's causing it? I don't understand why the tq convertor would be unlocking, why is that?

 

Not sure if yours has the same tranny as mine (45RFE) but I had a similar problem with the lock-up clutch unlocking and then relocking when driving at highway speeds. It turned out to be the Throttle Position Sensor. Either test it (I think there's a Sticky at the top of this section that explains how to do it) or just try a new one , they're not that expensive. Do it sooner rather than later as will eventually destroy the clutch.

 

It is probably in OD but it will then drop another few hundred RPM once the torque converter locks in. That's what Magnet was trying to say

 

Oh alright I see. Why would it take so long to lock in though? And then why would it downshift randomly back into 3rd?

 

Well as the terrain changes it will lock and unlock just like when it has to drop down a gear to go up hills. It should not do it constantly but on a flat straight away it should lock in and stay locked in. This is when you get your best fuel economy

 

Yeah, but the thing is it takes awhile to lock in and then randomly unlocks and downshifts on FLAT terrain. Maybe this is a part of my fuel mileage issue too... I've been getting like 13.5 all highway.

 

the problem is, he's saying it drops from 2200 to 1800. That's only 81% overdrive, and our transmissions are 69% OD. So if it went into OD and locked the TCC, the engine should be at 1600.

 

Bingo. Sorry if I'm being confusing guys. But yeah, it takes awhile to drop to 1800, but did not once drop to 1600 as you say it should be at (also, if it matters I have 31 inch tires and 3.55 gears). I'm just kind of clueless as to what to check first. I was thinking TPS maybe, but it seems like it could be a solenoid in the trans. I'm just not sure.