Automatic Transmission High RPM Shifting

[NovceGuru]

Hello gurus.

93' (9/92) bmw 525iA m50tu here. My driveway is located at the bottom of a blind hill and being how I like to baby my car, I hate reving out to 3500-4000RPM to shift when everything is cold in the morning. (More so in the winter than summer, summer is 2900-3200 RPM) I have read this is done to warm the drivetrain up but that seems a little high. I accidentally have found that if you slip down into sport mode then back into drive before speeding up on the road, it shifts like its warmed up. Is this bad to do? If not then maybe somebody else with the same problem can use this trick. I like being able to moderately accelerate @ 2500rpm (like a grandma). Thanks

NovceGuru

[Yiorgos]

I leave my car to idle for 2 minutes or so (I watch my clock tick 2 mins after whatever time it displayed when I start my car) while it is parked and handbrake on. I'm not sure if there are any ill-effects in doing this, but I find the car shifts a lot better after this, rather than taking it to 4000rpm before shuddering as it changes to 2nd!

[genphreak]

Dunno how many will reply to this thread... I am no guru, I break more than I mend. Many others like me here... though some have a lifetime's BMW experience in comparison to us So JIC few others do, here's my 2c:

Hello gurus. I accidentally have found that if you slip down into sport mode then back into drive before speeding up on the road, it shifts like its warmed up. Is this bad to do? If not then maybe somebody else with the same problem can use this trick. I like being able to moderately accelerate @ 2500rpm (like a grandma). Thanks NovceGuru

Have you ever stopped to wonder why it shifts at higher points when cold? Is your car not telling you something?

The biggest danger to a cold engine is LOAD. Revs are not your enemy, it is far better to maintain low load at higher revs than use low-end torque. That is why BMW increase the shift points when the engine is cold.

If your tranny bangs through the gears, fix it- it will shock the engine and when cold cause a lot more wear.

Of course moderation is a good thing, so you don't over-rev the engine.

Best way to treat the car when cold is to avoid parking at the bottom of hills; as this means driving back up them when cold (leave it up the street perhaps ?). Each day doing this will add more wear on your engine- as you probably know 80% of its wear is when cold, putting it under heavy load when starting out adds to this ratio.

Driveways that go down steep hills are designed by architects rather than engineers

[pingu]

I thought the manuals said to drive off as soon as the engine is running (but keep the revs below 4000 until warmed up). I suspect that idling for 2 mins on a cold day will increase cylinder wear as the extra fuel (due to the "choke" being on) will wash away the lubricating oil from the top of the cylinder/psiton. Or something like that.

[pingu]

Just curious as to why load should be worse than revs for a cold engine? Any ideas anyone?

[Blitzkrieg Bob]

it's all ICV man....

I 'd check my trans fluid level, low level can make the trans act odd until it heats up and expands to capacity.

[genphreak]

Just curious as to why load should be worse than revs for a cold engine? Any ideas anyone?

Oil is very thick when cool. Pressure cannot be relied on to ensure good lubrication (the system doesn't work as efficiently as it does within normal operational temperatures). I think the most critical points are the main bearings and cylinder walls/piston rings, as the top-end is easy to get a good squirt across- it just takes longer to flow back to the sump Nick

[pingu]

I think the DME uses the coolant temp to perform the same function as a choke (I guess by squirting extra fuel through the injectors) - I've also heard that a faulty temperature sender can reduce m.p.g. as it fools the DME into thinking that the engine is not warming up.