Two Auto Trans questions - separation anxiety and test drives
07-25-2012, 12:44 PM
#1
Rennlist Member
Thread Starter
Two Auto Trans questions - separation anxiety and test drives
Two topics actually, not closely related.
First question: A seller has told me his car (which I have not seen yet) experiences drain back from the torque converter after it sits undriven for several days. This drain back leads to some piddling of tranny fluid on the floor. As a former owner of Labs and Weimaraners, this sounds like separation anxiety to me.
This separation anxiety is evidently a known and recognized phenomenon - https://rennlist.com/forums/showthre...errerid=100405 - and relatively benign. I also expect evidence of the leak to be around the fluid tank and plumbing. My question is whether fluid from separation anxiety is apt to travel and thereby mask other less benign leaks.
Second question: I have been advised that a proper test drive of an AT car should include downshifting before coming to a stop to trick the trans into leaving the stopped position in first. I don't really understand this. Flooring he accelerator with the engine off and key in run to listen for the solenoid makes sense and is something I do, but this downshift thing eludes me.
Also, two AT cars I have driven but did not buy had decidedly balky shift mechanisms that would manually downshift while the car was in motion but were a bitch to shift up to the highest range while driving. Is this likely a combination of driver error and the fact that both cars had "floating" T - handles or is there something about these auto boxes that I don't know?
Thanks for your advice and assistance. This forum is simply awesome.
First question: A seller has told me his car (which I have not seen yet) experiences drain back from the torque converter after it sits undriven for several days. This drain back leads to some piddling of tranny fluid on the floor. As a former owner of Labs and Weimaraners, this sounds like separation anxiety to me.
This separation anxiety is evidently a known and recognized phenomenon - https://rennlist.com/forums/showthre...errerid=100405 - and relatively benign. I also expect evidence of the leak to be around the fluid tank and plumbing. My question is whether fluid from separation anxiety is apt to travel and thereby mask other less benign leaks.
Second question: I have been advised that a proper test drive of an AT car should include downshifting before coming to a stop to trick the trans into leaving the stopped position in first. I don't really understand this. Flooring he accelerator with the engine off and key in run to listen for the solenoid makes sense and is something I do, but this downshift thing eludes me.
Also, two AT cars I have driven but did not buy had decidedly balky shift mechanisms that would manually downshift while the car was in motion but were a bitch to shift up to the highest range while driving. Is this likely a combination of driver error and the fact that both cars had "floating" T - handles or is there something about these auto boxes that I don't know?
Thanks for your advice and assistance. This forum is simply awesome.
07-25-2012, 01:19 PM
#2
Under the Lift
Lifetime Rennlist
Member
Lifetime Rennlist
Member
Overfilling of the reservoir is perfectly normal for an AT on sitting for a while. There is a check valve somewhere in the system to limit drainback from the TC, but even with that, the reservoir level will be above the filler opening on sitting. Still, when the reservoir overfills on sitting, leaking and puddling under the tranny is not normal. That means either the cap on the reservoir is loose, has a defective or missing seal or the overflow hose is loose/off/missing/split. Or the pan gasket may not be sealing if the leak is from tha pan, which also fills above the gasket level on sitting.
At some point around 88, Porsche changed the shift program so unless you pulled the shifter down to the "2" position at a stop or mashed the throttle, the car would start out in 2nd gear. When driving with the shifter in the "2" position, the tranny should drop into 1st at about 6 MPH as you slow down to make a stop. This downshift is usually a rather noticeable "clunk". At any higher speed it should stay in 2nd gear, again, unless you mash the throttle. At one point my car developed a sticky 1-2 shift valve and stopped dropping into 1st under any conditions. Fluid change and some trans additive eliminated that problem and it has not come back for 5 years or so.
I'm not quite sure from your description why the tranny would not "upshift" as easily as downshift other than the Bowden cable may be maladjusted. Also, if the shifter felt different in that direction, the cable may be frayed or the sheath end fitting could have come off its bracket. Downshifting pulls on the cable while upshifting pushes.
At some point around 88, Porsche changed the shift program so unless you pulled the shifter down to the "2" position at a stop or mashed the throttle, the car would start out in 2nd gear. When driving with the shifter in the "2" position, the tranny should drop into 1st at about 6 MPH as you slow down to make a stop. This downshift is usually a rather noticeable "clunk". At any higher speed it should stay in 2nd gear, again, unless you mash the throttle. At one point my car developed a sticky 1-2 shift valve and stopped dropping into 1st under any conditions. Fluid change and some trans additive eliminated that problem and it has not come back for 5 years or so.
I'm not quite sure from your description why the tranny would not "upshift" as easily as downshift other than the Bowden cable may be maladjusted. Also, if the shifter felt different in that direction, the cable may be frayed or the sheath end fitting could have come off its bracket. Downshifting pulls on the cable while upshifting pushes.