Using lower gear going down steep grades

[AlabamaDan]

Where I live there are lots of hills, mountains to some. One stretch of road in particular is a steep downhill grade about 1 mile long. In lieu of riding my breaks down the hill, I've been pulling the shifter out of D into 3 and letting it coast. At the top I'm at 40mph and at the bottom I'm just under 50mph. So, the lower gear holds me back. Speed limit is 45. Works great - am I doing any harm to the transmission?

[elwesso]

No thats probably better than using the brakes. The only real "damage" you could be doing is just by shifting that one extra time, which over the course of a million shifts is a drop in the bucket.

If you were to break down the cost, its probably cheaper to do that than trash the brakes.

[Q45tech]

$4000 transmission/150,000 miles ~ 2.66 cents per mileBrakes pads plus prorated rotors on 150k [4 sets of rotors] 5 sets of pads + labor ~$5,000.

Probably a wash or weighted more toward using transmission as more economical. Except based on gasoline used which might favor wearing out brakes faster.

Editorial:

When you add transmission, tires and alignments and rotations/balancing, brakes you get about 8 cents per mile.

Not hard to see that the rest of car can consume another 7 cents to total 15 cents per mile

For some reason members seem to have a hard time wrapping their brains around the prorated logic of total costs to operate. Monthly payments mentality without any thought that the rest of expense usually equal or exceed the payment. With new cars the deprecaition eats you up and then the repairs for the depreciation.

[Jesda]

Transmission might be safer too. Would certainly be a pisser if you ran out of braking ability in the middle of a mountain pass.

[Rex]

The only thing I see missing from Q45tech's math is that you can (and probably do) the labor on your brakes, the transmission isn't very DIY.

[jamesmost]

Danny what up - sent u an e-mail - jAMES

[maxnix]

No thats probably better than using the brakes.

I'll disagree. Brakes are a lot cheaper than trqnsmissions. The wear on the transmission is accelerated when using it as a brake, whereas brakes are designed specifically to turn enrgy (momentum) into heat.

Do you hvae the auxiliary ATF cooler? Running OEM, Brembo, or other rotors? DOT 4?

[elwesso]

How does the trans wear out more when you're just coasting in gear?

[Q45tech]

Transmissions are speced and tested by number of shifts ............100,000 shift cycles. Same with lockup clutch only so much material which get worn during engagement and disengagement. How many shifts per mile is the life factor.

Heck same with gear shift and electrical assemblies talking to TCU...........not many manually shift each gear.

[AlabamaDan]

I'm running all OEM.

I don't have a trans cooler (yet), so I didn't think about it getting too hot. I may just start using brakes instead as they're easier to change than a trans.

[maxnix]

How does the trans wear out more when you're just coasting in gear?

He's not coasting, he's engine breaking via the transmission. About the same stress and wear as accelerating I would think.

[Skibane]

There will be some ATF heat buildup, since the torque converter is still loaded against the engine's compression braking - and heat tends to shorten the transmission's lifespan.

I use compression braking quite a bit on my motorhome - On long downgrades, 14,000 pounds is a lot for the service brakes to handle by themselves! Going downhill, the ATF temperature gauge never shows the fluid getting as hot when it was when ascending the hill, but it still warms up significantly.

IMO, a little extra ATF heat (and shift wear) is probably preferable to overheated brakes - which makes compression braking suitable for long, steep downgrades only. OTOH, downshifting at every stoplight just to save your brake pads is penny-wise and pound-foolish.

[maxnix]

IMO, a little extra ATF heat (and shift wear) is probably preferable to overheated brakes - which makes compression braking suitable for long, steep downgrades only. OTOH, downshifting at every stoplight just to save your brake pads is penny-wise and pound-foolish.

True, it is about margins of reserve performance. Cheaper to acheive reliably in brakes than in transimissions over the long term.

[AlabamaDan]

Ok. Sounds like we're in agreement that riding the brakes isn't good. Neither is downshifting and letting the transmission do the braking.

Here's how I handled the hill today. I left the car in "D" and coasted. When I reached 50mph I would press the brakes for a second or two until I'm at 40mpg then coast again. I had to press the brakes 5 times coming down this one mile stretch.

Think this might be best? Of course if the guy in front of me just a brake rider it might not work so well.

[maxnix]

Yes, it is best to gently apply the brakes then let them cool by traveling without further application.. The worst thing to do is to use them hard then stop at the bottom and let the built up heat cook the fluid.

IMPORTANT NOTE:

Spoke with Joe today, remanufactured transmissions are still $2,200 + shipping less $400 core exchange + shipping.

Wonder what my wife would say with 3 transmisions in crates in the garage?
Modified by maxnix at 10:33 AM 11/27/2007

[elwesso]

Yes, it is best to gently apply the brakes tehn let them cool. The worst thing to do is to use them hard then stop at the bottom and let the built up heat cook the fluid.

IMPORTANT NOTE:

Spoke with Joe today, remanufactured transmissions are still $2,200 + shipping less $400 core exchange + shipping.

Wonder what my wife would say with 3 transmisions in crates in the garage?

any how long that price will be good for?

[Q45tech]

I forgot to post about RE4R03A transmission prices: we still pay $1850 wholesale delivered to our shop...........they pick up old core at same time.

There was some confusioning posts in past about some price increases.

We don't markup up to MSRP just use~~25%= $2350 +$600 labor + new rear main seal + new transmission mount + aux heat interchanger/cooler .$3200 + sales tax.

We know these Nissans remanns last 100k so remember to allocate 3.5 cents per mile for the next one...............plus 5-7 years of price inflation.

Not too many trannies are sold these days as the charges are worth more than the Q. People usually bring in their own junkyard units and pay extra labor...............One Q got swapped 3 times until the customer found a decent unit..................that extra labor would have brought a Nissan remanned