Got the tranny checked, got good news and bad news

[mzarifkar]

Background:
I had a coupon for a free diagnostic service so i went out full of optimism to see what was causing my lack of reverse gear (slipping really, it will still go)
I was always hoping that it was fluid related and that the trans was low on fluid causing this along with pendulum shifting. Another sympton leading me to believe that it was fluid related was that whenever cold, reverse worked better. And after a sudden stop, the car would be in neutral and then suddenly lurch into gear. Anyone have anything on this...

On to the diagnostics:

The good news: The fluid was not burnt and up to level

The bad news: I cant blame the fluid

sooo.... that kinda eliminates the easy fix...

I did have one question for the Trans wizards among us. The BMW dealer wont check fluid unless its cold, the AAMCO guy said it didnt matter ( he checked it with after i drove over there for 20min on highway, so it was up to temp) who is right? what to do

M

Edit: I do have a functioning first gear, and engine braking too

[calmloki]

Well... just did a tranny service on my '93 525i, using these directions from Pelican - same model trans as mine. Checked when up to temp. Dunno if fluid would show lower (fluid up in the system, not drained back down) or higher (fluid expanded due to heat).
http://www.pelicanparts.com/bmw/tech...Fluid_Auto.htm
HTH, Tom Walrod

[632 Regal]

check it yourself, do you have a dip stick or have to go under the trans? I do believe that it has to be warm to the touch, not burn your hand but be quite warm to the touch for proper temps. And YES it has to be running, go through each gear before checking with the brake on.

[F4Phantom]

after just having got my trans serviced, i buzzed the guy about it all. Aparently you need the car running because thats the only situation where the torque converter is in its "natural" state putting correct pressures through the auto system. When you replace the fluid you are ovbiously only replacing around half of it as the other half is in the TC. If you find the fluid is burned (they put an additive in it to react to heat to turn it a darker colour I belive it does not actually burn) then you get them to do a trans flush which changes 100% of the fluid while flushing it with engine running, costs $100 more over here. Also burnt fluid is not the cause it's usually a symptom of the actual problem so replace it and it will likley happen again untill the problem is fixed.

[wingman]

Cold??? sheesh! Every auto car I've ever owned from a '71 LC Torana (Go Brocky), To my wife's current Subaru has said to check the fluid level at 'running temperature' with the car running and in neutral.

[wingman]

Further, On page 68 of my E34 manual it clearly states that the car must be at operating temperature (80c) and be in either Park or Neutral to check. Can I suggest that the stealer needs to get the car cold so they can warm it up on their time and charge you at Au$150 per hour to warm it up.... Cynical? Who me???

[DanDombrowski]

The reason they won't check the fluid cold is because they would have to work on it right away. If it has to be cold, it gives them an excuse to have it for at least a few hours and get to it when they feel like it. (Ok, I'm kidding on that, but it might not be far off).

As for the slipping - Its probably because the transmission is missing a pedal to the left of the brake. If its missing the pedal, it ususally exhibits problems.

Ok, now that I've wasted your time twice, I can't say I have much good news for you. Most of the time people get slipping autos in reverse, they end up being told the trans needs to be rebuilt. Whether or not this is a correct diagnosis is true, I don't know, because people usually junk the car after that and buy a new one

[tim]

Dan- you're on a roll today!


Regarding the temp issue:
The reason for the temp spec is that ATF increases in volume as a function of temperature. A non-dipstick car that was filled at operating temperature would almost certainly be underfilled, since the difference in volume in a typical 12liter capacity system between cold and warm is over a liter of volume. The dealer was right, in the sense that to do it properly, you have to start with a cold tranny, and run it until it reaches spec temperature using a modic reader or a thermogun. Spec temperature (30c-50c) should be lukewarm to hot soup. If you can't comfortably have your hand in it, its too hot.

Regarding no reverse: I'm unclear on whether you have all forward gears and no reverse, or only first gear and no reverse. If its just no reverse, then in all likelihood you have a valve body issue. You can get a rebuilt one swapped out for your core (search on "Kirt"). A common problem of ZF 5speeds was that a little check ball in the VB would wear away and get lodged in the pressure relief bowl for the reverse clutch pressure line. Thus an otherwise functioning tranny would lose the ability to shift into reverse.

[Bill R.]

dealer is correct this time.. For me in arizona the temp of the fluid is not much above the ambient temp in the summer to have it at the ideal temp for checking..There's a lot of expansion in this fluid as the temp goes up so if its too warm when you check it it will be inaccurate and the fluid level will be too low. Here's a chart from the older ones like yours when they still had a dipstick , you can see how much the level changes due to small temp changes. I did a 528 not too long ago that was hesitating going into forward gears and reverse and slipping when coming to a stop and taking off. I changed the filter and fluid and filled it up right when the fluid temp was on the low side of the scale 30C, worked fine after that.

[632 Regal]

dipsticks are cheating.