Is there a problem with forced downshifts?

[boatmax]

I have a great friend, who is a second generation auto mechanic, and he told me that for every forced downshift, it is damaging the transmission at the rate of losing 2 upshifts, due to transmission valves and fluid pressure. This was a general statement, and not Sprinter specific, and I wanted to hear back from the hard core mechanical guys on this forum. I have only had my 2004 Sprinter MB Cruiser RV for 6 months, but have enjoyed the downshifts instead of hard braking. His response was that I could replace a lot of brakes for the price of a transmission rebuild.
The OTHER Max

[Aqua Puttana]

I'm not hard core mechanical, but I'll give my opinion. I don't necessarily agree with the one downshift equaling 2 upshift formula. I do agree that regular downshifting to slow your vehicle is harder on the transmission and potentially a more expensive route than using your brakes.

I personally shift down before steep inclines especially when heavily loaded or towing my trailer. I do not regularly downshift to slow down in any vehicle unless I'm heading down a steep incline and want to control a heavy load. FWIW. vic

[aljimenez]

I have downshifted every vehicle I have driven (I'm 67 now), both manual and automatic. I have heard this suggestion that an automatic transmission is more expensive and why not simply lean on the brakes instead since they are cheaper. Well, most of the people I know replace brakes at least twice as often as I do, and I have yet to have needed any transmission rebuild in all the years I have been driving downshifting. Not an endorsement nor based on any scientific data, I am just sharing my own data... Al

[Mrdi]

Downshifting for me is to keep the RPM between 2000-2600 when the RPM drops as a result of incline or even on the flat when the trans shifts to 5th when my speed is only 40 mph. I also downshift on steep decline in the mountains and still keep the RPM below 3000.
I would not downshift to slow my speed when coming to a stop in traffic, that is what the brakes are for and it would seem to me that would be abusive use of the tranny.
All my vehicles before the Sprinter (VW,BMW,Porsche, Miata) have been manual, and downshifting when in traffic to slo the vehicle seems abusive even with a manual.

[sailquik]

I do not think that a manual downshift causes any issues for the Sprinter NAG1 transmission at all.
If you downshifted through all 5 gears (5th/4th/3rd/2nd/1st) every time you came to a stop sign or
coasted up to a stop light, you might wear the shift linkage switches out, but I do not believe you
would hurt the transmission.
Actually, a Sprinter with the NAG1 Transmission will downshift itself if you are running along in cruise
control and start down a hill that is too steep for the engine to control your speed in the gear you are
in.
My '06 T1N 3500 downshifts all by itself on a particular downgrade I travel on my way home from work.
I let off the throttle, the LOD goes to 0% (zero), the fuel use goes to 0 (zero) GPH, and about half way down
the hill the trans shifts from 5th to 4th.
I make a hard RH turn at the bottom of this hill and I will downshift another gear (manually) as there is a fairly
steep grade leading up the road I turn on from this intersection, so being in 3rd gear gets me going, keeps the
% LOD down for good mileage, and gets me back up to speed pretty quickly.
Since the ECM and TCM are programmed so you cannot downshift and over rev the engine, I do not believe the
fluid in the torque converter really cares if you downshift. It just churns the oil/fluid in the torque convertor
a bit.
Just my opinion... 100K miles.... no serious RSN and no know transmission issues..... even from running in 4th
gear, loaded to around 10-11K lbs. (van and 14ft x 7 ft cargo trailer) all day long into a 20 knot head wind.
Roger

[Doug]

The Sprinter is designed to downshift for you to provide engine braking. If you have the cruise on and you start down a hill and your speed increases over your set speed by 3 MPH it will down shift for you, the same as it will downshift if you drop 3 MPH below set speed. Even if you are not on cruise it will also down shift thinking you need braking when speed climbs with little to no throttle. I see no problem down shifting for engine braking when you want it. There are times when I have to force a up shift to over ride the downshift when I do not want the engine braking. The higher the rpms the more engine braking you will get. I have seen 10 PSI of boost at 4200-4300 RPMs giving more engine braking.

Doug
04 Topless 140 3500

[talkinghorse43]

I'm wondering if downshifting might even be good for the NAG1. Maybe it leads to more balanced wear since forces on clutches are reversed 180 degrees when using engine braking?

[Diamondsea]

I only downshift for 3 reasons. First is on long mountain downgrades to save brake wear and avoid possible brake fade due to overheating. I only downshift 1 or 2 gears so I am still using the brakes intermittently. The second instance is to help slow down when making a "panic" stop. The third reason is on long curvy upgrades if the transmission seems to be "hunting" between gears as I slow for the sharp curves then accelerate then slow again. In this case I keep it in the lower of the 2 gears to avoid the "hunting" back and forth. I do believe that excessive downshifting will shorten tranny life and, yes, brakes are far cheaper.

[NelsonSprinter]

I remember 1 user on here snapping a camshaft by forcing a downshift to above 3500rpm, so I never downshift above 2200RPM, I brake to usually 2000RPM then downshift when going down a long hill, resulting in a new RPM of 3000 .

[Doug]

There had to be a problem with the camshaft to have that happen. Plus you can not force a downshift, you can only suggest to the ECU you want to change gears, the ECU has the last word on downshifting. Before I changed to taller tires the ECU on it own would downshift above 3500 because of the high RPMs at highway speeds due to the shorter tires. So even the ECU will downshift to above 3500 RPMs.

Doug
04 Topless 140 3500
Now with 29.4" tires on 15" wheels