Automatic Transmission "Downshift" Engine Braking - PeachParts Mercedes-Benz Forum

deerefanatic · #1 08-28-2005, 08:51 AM

Hi, I have my 82 300SD and was just scared crapless at the price of a full set of brakes (rotors, pads, caliper rebuilds all the way around.) I got them from Rusty though, so that saved me some cash....

Anyhow, I have found a way to save my brakes, when coming to a stop sign, corner, etc, I let off the gas pedal at the same time as normal, then after I hit about 50 mph, I kick the shift lever from D to S and allow engine braking to slow me. I then lightly apply brake to peal off about 10 mph of speed from 40 to about 28-30. I then kick shift all the way to L and apply brakes, bringing myself to a nice stop, without using the brakes to drag myself down.

My question is, is this hard on my Tranny? I wouldn't think that the engine braking itself would be, but does the "manual" downshifting used to accomplish this feat detrimental to the tranny's health? If so, I wont do this anymore as brakes are free compared to transmission costs.

Thanks guys!

Jim H · #2 08-28-2005, 09:00 AM

You will hear various opinions.

Mine:

It will cause some additional wear to the friction materials in the transmission, but your car will probably be scrapped or retired for some other reason, such as terminal rust or an accident, before you wear out the transmission.

Your mileage may vary...

Best Regards,
Jim

pawoSD · #3 08-28-2005, 10:14 AM

If it was me I'd much rather continue replacing front pads and rotors into the future than add all that wear to the tranny, it even says in the car's manual not to use the tranny as an engine brake, it causes additional wear and heat buildup. A tranny costs WAY more than brakes......pads are like $30 a set for the front....and the rotors maybe $50apeice? That should last years....a tranny is thousands.

I've had the same rotors and pads over a year now, I still have 60% of the pads, and probably 80% of the rotors left, and I brake a lot, mostly city driving, and at high speed (55mph), so I don't worry about it. Also, its only the front brakes that will wear out, the rear ones last forever.

All in all I'd just go by what the manual says and not use it for engine braking....

tangofox007 · #4 08-28-2005, 10:29 AM

You have, no doubt, heard the saying "Penny wise and pound foolish." Saving your brake pads could be a very expensive proposition.

Glinko · #5 08-28-2005, 10:45 AM

I used to downshift a lot when coming to a stop. I don't do it anymore, although I have no idea why I discontinued the practice....actually that just occurred to me.

Wes Bender · #6 08-28-2005, 12:17 PM

Unless something is wrong with your brakes, the usual cause of excessive brake pad/disk wear is driving style. If you want to get on it hard and brake hard, something has to wear, i.e. your brakes. Why not plan ahead and let the engine (in top gear) slow you down a bit and then only use the brakes for the final slow to stop? I wouldn't shift down to slow the car. That was normal before good brakes were available, but isn't really justifiable now.

Of course, if you prefer to drive aggressively, you get to pay the price.

My pads on the '82 300D last about 80k to 100k miles. (And I'm seldom late to an appointment either.....)

Wes

deerefanatic · #7 08-28-2005, 12:51 PM

No, I'm not an "agressive" driver really. I was only using the tranny to slow me because I thought "what the heck, if it is free braking, then might as well use it". BUT.........if it is hard on the tranny, I will discontinue the practice immediately. I'd like to keep this tranny in this car for good, and I plan on keeping this car unless a total-destruction wreck takes it from me. As it is my first car, I'd love to keep it and maybe restore it some day in the future, might make a great family heirloom.

thanks for the input!

pawoSD · #8 08-28-2005, 06:45 PM

These cars slow significantly just leaving them in the highest gear "D"....especially from speeds 45 or greater. If your driving 35 or below, just drive around all the time in "S" then it will slow you down even more when you let off the pedal. In residential areas of 25-35mph I often don't use overdrive, there's not really much point, plus the added drag/braking effect of being in third gear does help save on brake usage....

Our stupid minivan is a different story, if the surface is level or even a slight grade, its speed INCREASES as it rolls along, even if you don't touch the pedal, thus requiring braking on occassion, and complete brakes to slow from whatever speed. Needless to say, when its driven as a Daily Driver it eats a set of pads and rotors once every 1.5 years or so. Good thing its not a daily driver for us...

Oh yeah, check engine light on again too....

H-townbenzoboy · #9 08-28-2005, 07:15 PM

What I like about these cars is when you're in a traffic jam, you don't have to hit the brakes all of the time, just tap the accelerator pedal a tad, and let off and it'll slow down, when it moves, tap the accelerator again, and when it slows down, it starts slowing down like the brakes are on, in a gasser, I'd be constantly on the brakes. That's one way to save brakes. Another way is when I'm getting off of the freeway, I just let it coast down to speed, and when it coasts down to say, 45-40, I start braking. It works very well on those freeways that are depressed below ground and the offramp is an incline, in situations such as those, I'll just coast nearly all the way to the intersection and hit the brakes when it hits 30.

pawoSD · #10 08-28-2005, 08:52 PM

Quote:

Originally Posted by H-townbenzoboy

What I like about these cars is when you're in a traffic jam, you don't have to hit the brakes all of the time, just tap the accelerator pedal a tad, and let off and it'll slow down, when it moves, tap the accelerator again, and when it slows down, it starts slowing down like the brakes are on, in a gasser, I'd be constantly on the brakes. That's one way to save brakes. Another way is when I'm getting off of the freeway, I just let it coast down to speed, and when it coasts down to say, 45-40, I start braking. It works very well on those freeways that are depressed below ground and the offramp is an incline, in situations such as those, I'll just coast nearly all the way to the intersection and hit the brakes when it hits 30.

Same here! I love that feature.....our gasser van can go up those incline ramps and barely lose 10mph!!

Its very annoying....especially if I drive it and I've been driving mine a long time.

#11 08-29-2005, 03:02 AM

In the "How to Keep your Volkswagen Alive a Manual of Step by Step Prodecedures for the Complete Idiot" it specifically mentions this topic.

Even with auto tranny expensive mercedes, the idea still applies.

Brakes are WAY cheaper than almost ANY component of the drive train system.

My concern would not be with the transmission so much as the drivesaft rubber joints.

Those thing do not take abuse so well. (and they are SPENDY!)

I eat brakes up fast but ya know...I drive really fast and brakes a cheap and easy to replace

I figure its not worth shocking my engine at every stop sign.

Now when it comes to the occasional downshift for a hill or 100mph-0mph stop...then I will usually try to give the brakes a break rather than use them for all the load. After you drive a car with crap brakes you know when you are abusing them and just merely using them

Thread Tools
Show Printable Version Email this Page
Display Modes
Linear Mode Switch to Hybrid Mode Switch to Threaded Mode

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
FS 1982-300SD Engine & Transmission	jim16671836	Mercedes-Benz Used Parts For Sale & Wanted	3	06-03-2005 11:35 AM
300D non-turbo engine, transmission	Joseph Bauers	Mercedes-Benz Used Parts For Sale & Wanted	1	05-10-2004 01:21 PM
Automatic Transmission Fluid E230	BlackMB77B704XM	Tech Help	0	09-23-2003 10:32 PM
Is this true? Moisture and MBZ Automatic Transmission Shift Handle	haasman	Tech Help	6	05-30-2003 03:14 PM
M116 removal from 82 380SL	rstarkie	Tech Help	3	11-14-2002 07:03 AM