Auto: prompt deceleration when off the gas

#1
Chaps,

Re 3500 Auto
I’ve noticed more recently that whilst driving in 3rd gear and then taking foot of the accelerator, the car decelerates significantly. If put into neutral it is much less so.


My ‘limited’ understanding was that being in Neutral or Drive should have a negligible effect on the distance the vehicle travels when the accelerator is not pressed because the torque converter disengages the engine below predetermined RPM levels.
Not being able to drive another P6 auto, I can’t make a comparison.
The auto box was reconditioned 17 years ago and 50k miles.
I appreciate the box and transmission won’t behave like a modern auto.
This deceleration feels like but isn’t the brakes dragging.
Is this a sign of wear or does the bw65 have this notable slowing down effect.
Up until now I have successfully avoided auto box concerns since the earlier work.
Fluid looks and smell ok.
Any discussion welcome

Thanks
Simon
 
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#3
Hi
Good point, potentially, but idle, neutral and general driving don’t appear to be an issue. Will check though.
General Mpg is a concern ( despite carbs and electrics in good tune, IMO) and I’m trying to confirm if an auto gearbox issue is a factor. I can’t recall the ‘ drag’ effect in want of a better term, when accel pedal released being so prominent.
Thanks
 
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mrtask

Well-Known Member
#4
Have you used your reserve fuel tap recently? Despite my Pet Res knob not smoothly returning properly all the way back to the centre console after a fill-up, I didn't twig that the tap was sticking, half open. At higher speeds there wasn't enough juice getting through! Doh!
 
#5
My reserve tap is not used due to using an electric pump.
It could be a delivery issue but the engine doesn’t feel starved of fuel.
I need to drive another p6 to compare.
Feels like driving with the brakes on
 

harveyp6

Well-Known Member
#6
The only selector position that gives engine braking is "1", there shouldn't be any in any other gear, and I can't think of anything wrong in the transmission that could cause the same thing while driving in TOP unless there were other problems.
 
#7
Tanks Harvey,

From your experience do you see or feel an appreciable engine braking effect when releasing foot of pedal in P6s. As mentioned, I have not been in another P6, thanks
 

harveyp6

Well-Known Member
#8
No, apart from in "1", other than that it should pretty much coast when you lift off the gas. That's why autos tend to wear out brake pads quicker than manual cars.
 
#9
Thanks again, that was always my understanding.
That may eliminate the auto box, and sounds like general rolling resistance is high.
Diff, prop shaft, UJ, even fuel delivery all under suspicion now.
Thanks for the comments
S
 

Demetris

Well-Known Member
#10
I cannot see how fuel delivery or anything engine related would be a likely cause. When you lift off the accelerator, does the engine return immediately to idle speed as it should?
 
#12
Hi.
Apologies for hijacking this thread, but my V8 auto BW 35 does not return to idle when releasing the accelerator whilst cruising, it just stays at normal cruising revs. Is this abnormal?
Thank you
Glen
 
#14
Unlike yours Rich and Demetris, mine doesn’t roll along, it slows down notably, but I do need to check if the road speed and engine revs fall at similar rates.
 
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