I've been downshifting a little - trying to save some brake wear...

But it occurs to me that the sudden rev increase and clearly louder engine noise is due to the rev matching "feature"...

Right?

So one can assume that any brake wear would be easily offset by reduced mileage over time, by constant up-reving of the engine. Right?

 

I'm not sure how much the rev-matching affects gas mileage, but I can't imagine it would be noticable. But don't you love the it!

And besides, do any of us really by the G for the gas mileage? It's too fun to drive to worry about the difference between 20 and 22 mpg. I would have bought a Prius if mpg was a big concern.

 

dont put too much strain on the tranny and do that everytime. whats cheaper? tranny or brake pads?

 

i had a friend who had the same philosophy. needless to say his tranny went in under 80k. brakes are going to wear out. they are also not expensive if you can or know someone that can put them on. but constantly downshifting an AT is prob not the best thing to do. i dont even want to know how much a tranny for our car cost if needed to be replaced.

 

Your friend has a G? Downshifting using manumatic to do engine brake/slow down is bad for tranny. Automatic doesn't have the clutch to take the abuse, thus it hurts your tranny. Downshifting to immediately accelerate won't be a problem. When you leave it in D and you step on the gas it downshifts to immediately accelerate, same concept.

 

Lots of opinions here.

Owners manual discusses using the engine/transmission for engine braking - so occasional use must be within the parameters of the unit's design.

I believe it would also depend on at what point you were engaging the lower gear. Downshifting at the appropriate point would create one measurable load on the tranny, downshifting to a lower gear at higher speeds would create another.

I use my transmission in much the same way as I would a manual - downshifting and applying brakes to slow the car. I don't, however, engage the lower at a point which would lock the rear wheels if you know what I mean.

The rev-matching downshifts were built into this tranny for a reason - to be used. If someone ate their tranny in only 80,000 miles, I wonder what technique he was using and what else he was doing to it while he wasn't downshifting. Aggressive launches maybe? Constantly upshifting at redline? Power braking? Lots of things go into the mix..

Use it how you see fit.

 

I've always been of the philosophy that the engine should drive the wheels, the reverse is true when down shifting...the wheels are actually driving the engine.

I've been told that on air cooled general aviation aircraft engines this is BAD. Supposedly it causes piston ring problems and in general causes internal parts to wear more since they are being put under loads that are opposite or different from what they see in normal operation.

I'm not sure that this is an accurate correlation, I do know that aircraft engines are not made with close tolerances, but I still think that brakes are cheaper than engine and drive train components.

 

I asked this question about a year and a half ago. Some of the more informed members related that that torque converter had viscous coupling, so there is no mechanical parts to wear/stress. However, if there was any concern, it was the stress on the crankshaft and engine. I don't think that there would be an excessive amount of stress on the rods unless you were downshifting bringing the rpms near redline (if that is even allowed in the manual shift mode).

g4ian

 

Engine braking to save pad wear to n-t-s (not too smart). An engine is a terrible thing to waste. Pads & rotors are cheap. Engine braking is for 18-wheelers and long Rocky Mountain decents, not for your stop-n-go.

 

Today as I'm driving home I'm manually shifting from gear to gear. I run through 1st, then 2nd, then 3rd. A car pulls out in front of me a bit ahead that causes me to slow. I ease throttle and then release it completely to wait for the guy to clear the lane (he's turning now...) As I do this I feel the tranny/engine load as I slow in 3rd.

As I do this I think of this thread. What I'm doing is no different than using the engine to slow the car while downshifting.

For those that say downshifting is bad for the auto tranny, what would you do under these circumstances? Upshift to 4th to reduce load? Seems unreasonable to me. I cite the owners manual for the 05s - refer to bold:

Shift ranges up or down one by one as
follows:
1M
,
+
2M
,
+
3M
,
+
4M
,
+
5M
5M (5th):
Use this position for all normal forward
driving.
4M (4th):
For driving up or down long slopes where
engine braking would be advantageous.
3M (3rd) and 2M (2nd):
Use for hill climbing or engine braking on
downhill grades.
1M (1st):
Use this position when climbing steep
hills slowly or driving slowly through
deep snow, sand or mud, or for maximum
engine braking on steep downhill grades.

But what do they know? Right?

 

Ok I asked the question to get this good feedback...

The issue of abuse to the engine / transmission is valid - but a bit mitigated by the fact that I will not own the vehicle in 7 years. I am leasing - but there is a remote possibility I might buy and re-sell at the end of the lease. (I know someone who is already thinking of buying it from me if the conditions are right) So since he is a friend - and the 25% likelihood that we go through with it - I obviously do not want to abuse a vehicle that he might end up buying.

It's a shame - the "manumatic" is of such little use to me now