Quick OD question, and a few small transmission questions

[Guest imported_Fox W.]

Hello all, thanks again for the fantastic support offered in this forum, I think the general attitude here is remarkably mature with a high percentage of very intelligent people.

Anyway, sorry if I am wording this poorly, I'm certainly no mechanic. But is it normal that when you are above 50Mph and in OD and you take your foot fully off the throttle that the tranny falls out of over-drive? Mine always does unless I keep atleast a some pressure on the trottle, which I always do since I am paranoid about making the transmission do any more work than is nessisary.

Also when I am coming to a stop after having been at maybe 40MPH+ I notice a light (though varies in harshness) thud when I get to around 30,25MPH or less, I believe this is normal, right? But should it be able to be felt/heard?

Lastly, is it normal for reverse to be a bit harsher when putting it into gear than drive? Mine always has been, again it varies though, sometimes it's not bad at all, now and then it goes in pretty hard.

Like I said transmission issues scare me more than anything for some reason, so I wanted to ask about these things. No real issues so far, it shifts smoothly every time, never slips or anything, and I even had my ATF fluid professionally replaced at about 120k miles, which caused no new issues or improvement, just did it for good messure. (I've heard though it can sometimes be a bad thing for some high-milage cars.) Replaced the cooler lines at the same time since mine were rusted. Thanks again.

[Guest wally888]

Even tho you answer the question, I won't be able to provide an answer but:

When you are driving around 60 mph w/ foot on accelerator slightly, tranny in overdrive (rpm's?), then you lift foot (rpm's?)

May sound like a corelation w/ cruise, tapping the brake...............when overdrive disconnects, rpm's momentarily increase.

[2seater]

None of the issues you mention sound unusual. The torque converter clutch will unlock when you lift off the throttle, it is not shifting out of overdrive (4th gear). This is normal operation. The ECM sees the throttle is closed via the signal from the TPS and assumes you are slowing or stopping so the the engine doesn't stall as you come to a stop, analogous to coming to a stop with the clutch engaged on a standard transmission. The feel of the transmission shifting down to the next lower gear does vary some from car to car, but it usually is noticeable, particularly the shift to first gear around 14 mph. This may be related to the harshness of the reverse engagement also. The primary external item that affects shift feel is the vacuum modulator. It senses engine vacuum to determine the approximate load on the engine and uses this signal to vary the line pressure inside the transaxle, reducing it under high vacuum to soften and slow the shift, and raising it under low vacuum, like when accelerating, to speed the shift and firm up the clutch engagement to better absorb and handle the power applied. A defective modulator or a vacuum leak will make the shifts harder than normal. As for the reverse engagement specifically, I have seen articles about a modification to the servo to modify the engagement, but I have found that shifting into neutral first and then to reverse helps smooth the engagement sometimes.

[Guest imported_Fox W.]

That was very helpful and informative, thank you. It seems things are normal with my transmission then, only reverse has ever been what I would feel to be a little too harsh sometimes, and it's rare that it does that overal. I am first to admit that I am particuarly picky about everything being in order, smooth and quiet. Thanks for the info! Now if I could just find the mystery vibration that recently started that I hear when I go over bumps! (It's not the infamous brake rattle)

[DAVES89]

Over bumps? I would guess that your strut mount/bushings are starting to go bad. Just today replaced both front/rear struts and mount/bushings. All quiet on the western front.

[Guest imported_Fox W.]

I hope it's just that, that wouldn't be hard to locate then. It's weird though because I should mention that it isn't always just bumps, though it is 99% of the time. To explain, first off it's kinda variable, sometimes it seems like it takes more for it make noise, others it will happen if the engine surges just a litte to much, or if it's one of those times where the transmission gives a a bit more thump when going into reverse. Usually though it's bumps, but not big ones or hard ones, no it's usually most noticable when going over lots of small bumps or ripples in the road, so it likes high frequency vibrations. It's weird, and by ear I cannot even figure out where under the car it is coming from, I just know it's not heat shielding. This started after I had my steering rack, engine/mount/strut replaced (I forget which) and oil pain seal replaced. The rack had to be done several times (see my other post of that story) but I don't think thats the issue, it was installed very well, it's center and tight. So I guess the engine mount thing is my only lead. *shrug* I've been thinking of taking my car to a suspension/alignment/brake shop thats really good around here and having them go through the suspension and let me know what needs replacing and hope that they figure out where that noise is comnig from. Again I don't think it's loud, I have a hard time when pointing it out to passengers to get them to even notice it, I think I'm just sensitive to my car. I sware if my car has the slightest change I pick up on it. Thanks for your help.

[padgett]

Almost sounds like you need control arm bushings - has that ever been done or had them checked ?

[Guest imported_Fox W.]

Thanks for the reply, no I do not believe I have ever had those specifically checked. I've had all the struts/shocks done, and both front wheel bearings, usually if something else looks bad in that area my mechanic tells me, but I guess looks don't tell all with that sort of thing, right?

[Guest imported_Fox W.]

Founds that dang rattle, it turned out just to be a metal line that runs right along a heat sheild near the front, I don't know what the line is for but it was supposed to be snapped into a rubber restrainer that is there and wasn't, after doing that though it no longer could rattle against the heat sheild there. Before finding this I brought it to a pro alignment shop and they checked all the bushings and said it was in really excellent shape to their surprise.