Turbo / Exhaust Brake Problem...

[EdGarcia]

Ok, so I have a 2012 Ram 3500 with only 14k miles on it. When I first bought my Ram, the diesel exhaust brake worked awesome and kicked in/slowed me down as it was advertised and I used it all the time for daily driving, without the tow/haul mode activated. Again, it worked great!



Now, the exhause brake doesn't seem to be working/kicking in as it has. It no longer slows me as it had before. Going down slight grade hills or any grade hill for that matter... the exhaust brake does not kick in or slow me down at all. However, it will if I activate my tow/haul mode button... but as mentioned before, I never used the tow/haul mode feature for daily driving before.



I have scheduled an appointment at my dealers for this coming friday for a 15k maint service & oil change and have asked them to look into this issue. Has anyone experienced this before or have thoughts on what might have happened? Or have any thought on what I should have the service techs look at???



I don't want to go to the dealers and have them tell me that they have looked at it and everthing is fine, when I know how it drove/responded before. Any insight from you guys would be appreciated.

 

[Surefire89]

At first I thought you might have a dirty turbo which would be hindering it from operating and moving properly. But now I think it may just be a wiring issue or in the computer due to it being fully operational in tow/haul mode. Good luck

 

[Hoefler]

When not in tow/haul, the exhaust brake only works in the highest gear achieved and the road speed has to be fairly high, don't remember the exact speed. When using the exhaust brake with tow/haul, it is a totaly different animal. Can be aggressive, will down shift and work all the way down to 2nd gear, and when used with light brake pedal pressure, can be very aggressive and works mjuch better.

 

[rwitt]

Can you tell if the torque converter is locking while not in tow/haul? The ebrake will not activate if the torque converter is unlocked. Just thinking that for some reason the torque converter isn't locking while not in tow/haul mode. On my truck with 3. 73 gears, when not in tow/haul, the ebrake will engage at slightly over 30mph, 3rd gear or higher.
Rich

 

[EdGarcia]

Can you tell if the torque converter is locking while not in tow/haul? The ebrake will not activate if the torque converter is unlocked. Just thinking that for some reason the torque converter isn't locking while not in tow/haul mode. On my truck with 3. 73 gears, when not in tow/haul, the ebrake will engage at slightly over 30mph, 3rd gear or higher.
Rich

Ok rwitt, I drive this truck almost every day ... . how do I notice if the torque converter is locking? And if it isn't... how bad of a problem can that be if not addressed? I'm taking the truck in this Friday and still under full warranty... is this something the techs would also check without being asked to?? Just curious cause I'd like as much info to properly explain what is happening in the hopes the dealer/techs are experienced enough to know what to look for... .

 

[rwitt]

Have you ever noticed when you are using your ebrake and your speed drops below 20mph, that your ebrake quits working? Its like the transmission goes into free wheel mode. Thats the torque converter unlocking, and without it being locked the ebrake does not work. Lets say you are driving a steady speed in 4th gear, if the torque converter is unlocked, and you give it a little throttle the engine rpm's will increase 200 to 300 rpm's. Also when you let off the throttle, if it is unlocked the rpm's will drop considerably. When the converter locks up it can feel like another gear shift. A locked converter is like driving a manual transmission, the engine rpm's will go up or down as your speed increases or decreases in a gear because you have a direct connection between the engine and transmission.

I don't know if this is your trucks problem or not, just throwing this out there. Maybe someone else here can explain torque converter lockup better than I can. I'm sure the dealer tech will be able to diagnose this if it works in one mode, but not the other.

Rich

 

[Hoefler]

If not using tow/haul, the torque convertor only locks in the highest gear achieved. Exhaust brake will not engage unless the convertor is locked. I always use tow/haul and exhaust brake together and all the time. I have done this in my 08 and my current 2010.

 

[EdGarcia]

Here's another thing I just thought of... would increasing the tire size effect the way the exhaust brake works? I swapped out my stock 265/70/R17's for a bigger sized tire and went with 285/75/R17's Toyo Mt's. When I went to the larger tires, I had my dealer recalibrate my speedo for the larger tires. Would this effect the transmission shifting points/RPM's enough to throw the exhaust brake out of whack so to speak... and can that be calibrated as well?

 

[HBarlow]

Bingo! You have changed the truck's effective final drive ratio, probably significantly. Your truck probably has 3. 73 gears, possibly even 3. 42. Larger tires have effectively changed gearing to a much higher gear ratio. When you consider a 60% overdrive in top gear multiplied times 3. 73 or 3. 42 and then an additional percentage multiplier you may have a final drive ratio of 2:1 or 1. 5:1.

 

[EdGarcia]

Bingo! You have changed the truck's effective final drive ratio, probably significantly. Your truck probably has 3. 73 gears, possibly even 3. 42. Larger tires have effectively changed gearing to a much higher gear ratio. When you consider a 60% overdrive in top gear multiplied times 3. 73 or 3. 42 and then an additional percentage multiplier you may have a final drive ratio of 2:1 or 1. 5:1.

HBarlow... ok, so your response sounds certain the larger tires I am running may be my issue. Here's my question then. Is this something than can be addressed by some sort of calibrating via the trucks computer... or is this now the new norm for the way my truck's exhaust brake will work with these new tires?



And again, just to clarify... . this minor issue is only experienced when I run with the exhaust brake on by itself. The exhaust brake runs fine when used with the tow/haul mode activated.



And again... to all of you guys out there... I appreciate your insight and experience... . Thanks much!

 

[RonD]

If your not in TH mode it will do as you are saying, that is normal, the exhaust brake and down shifting is for slowing the rig down on down hils, if your empty, and not in TH why would you even want that, as far as the tire size, I can't answer it , so trp driving the truck at highway speed say 65 mph, decend on a long grade and take your foot off, and see what it does, then do it again same place etc in TH, I think you will get the idea.

Ok, so I have a 2012 Ram 3500 with only 14k miles on it. When I first bought my Ram, the diesel exhaust brake worked awesome and kicked in/slowed me down as it was advertised and I used it all the time for daily driving, without the tow/haul mode activated. Again, it worked great!

Now, the exhause brake doesn't seem to be working/kicking in as it has. It no longer slows me as it had before. Going down slight grade hills or any grade hill for that matter... the exhaust brake does not kick in or slow me down at all. However, it will if I activate my tow/haul mode button... but as mentioned before, I never used the tow/haul mode feature for daily driving before.

I have scheduled an appointment at my dealers for this coming friday for a 15k maint service & oil change and have asked them to look into this issue. Has anyone experienced this before or have thoughts on what might have happened? Or have any thought on what I should have the service techs look at???

I don't want to go to the dealers and have them tell me that they have looked at it and everthing is fine, when I know how it drove/responded before. Any insight from you guys would be appreciated.

 

[Scrappy]

Here's another thing I just thought of... would increasing the tire size effect the way the exhaust brake works? I swapped out my stock 265/70/R17's for a bigger sized tire and went with 285/75/R17's Toyo Mt's. When I went to the larger tires, I had my dealer recalibrate my speedo for the larger tires. Would this effect the transmission shifting points/RPM's enough to throw the exhaust brake out of whack so to speak... and can that be calibrated as well?

Bingo! You have changed the truck's effective final drive ratio, probably significantly. Your truck probably has 3. 73 gears, possibly even 3. 42. Larger tires have effectively changed gearing to a much higher gear ratio. When you consider a 60% overdrive in top gear multiplied times 3. 73 or 3. 42 and then an additional percentage multiplier you may have a final drive ratio of 2:1 or 1. 5:1.

the tire size change is NOT the source of the problem. the size difference is only ~4%. I had 37's with 3. 73's (14% difference from stock) and that was significant but the exhaust brake still was VERY noticeable and still very effective.

 

[HBarlow]

the tire size change is NOT the source of the problem. the size difference is only ~4%. I had 37's with 3. 73's (14% difference from stock) and that was significant but the exhaust brake still was VERY noticeable and still very effective.

You're entitled to your opinion.

I couldn't find a 285/75/R17 tire on Tire Rack's website to compare the diameters and rotations per mile of the two sizes the op mentioned but even if the change is only 4% as you claim that is still the equivalent of shifting up one more gear. That will definitely reduce effectiveness of the exhaust brake just as there is a difference between retarding force between 6th and 5th or 5th and 4th.

I was only guessing when I wrote the earlier post because I didn't have a calculator handy but final drive of op's truck with OEM tires is 2. 31 and even with a 4% change created by larger tires the final drive ratio becomes 2. 22.

 

[HBarlow]

HBarlow... ok, so your response sounds certain the larger tires I am running may be my issue. Here's my question then. Is this something than can be addressed by some sort of calibrating via the trucks computer... or is this now the new norm for the way my truck's exhaust brake will work with these new tires?

And again, just to clarify... . this minor issue is only experienced when I run with the exhaust brake on by itself. The exhaust brake runs fine when used with the tow/haul mode activated.

And again... to all of you guys out there... I appreciate your insight and experience... . Thanks much!

Ed,

A gearing change cannot be recalibrated away. The speedometer read out can be reprogrammed to indicate a different road speed for a change in tire size but changes in final drive ratio as explained in post #13 are hard facts that create changes in truck performance.

Larger tires also reduce load startability to some degree and effective gear ratio in each gear from first through sixth.

I know the guys who love big wheels and tires don't like to acknowledge the trade-offs but they are indisputable fact. I can understand that the larger wheels and tires may provide increased traction in off road situations but I think most of them are added for the look not for function.

 

[EdGarcia]

Harvey, thanks much for the assist and clarification... it is much appreciated. I have a better understaning of the issue now. And in my specific case... you are correct sir, I specifically went for look and not function with these tires. The OEM tires in my opinion just didn't give my truck the look I wanted and the 285's did.

 

[Scrappy]

You're entitled to your opinion.



I couldn't find a 285/75/R17 tire on Tire Rack's website to compare the diameters and rotations per mile of the two sizes the op mentioned but even if the change is only 4% as you claim that is still the equivalent of shifting up one more gear. That will definitely reduce effectiveness of the exhaust brake just as there is a difference between retarding force between 6th and 5th or 5th and 4th.



I was only guessing when I wrote the earlier post because I didn't have a calculator handy but final drive of op's truck with OEM tires is 2. 31 and even with a 4% change created by larger tires the final drive ratio becomes 2. 22.

It is basically an inch(at MOST) difference in height. and at 60 mph the difference between them is only 2. 4 mph. that is NOT the same as another gear. the point is the change is so small in the overall scheme of things, it is not even noticeable from a power/driveability standpoint. the tire size change is not the culprit of this issue and it will still have the same problem with the stock tires.

 

[HBarlow]

Where is the spec sheet on that larger tire? How do you know its only a one inch and 2. 4 mph difference?

Ed says something changed in the way his truck operates. The only thing he has done to the truck according to his own statement is change the tires to a larger size.

ECM programming doesn't change and the physical characteristics of the VNT don't change. If the sliding nozzle was not closing fully, not providing full exhaust braking he would have a CEL and codes set identifying a severe problem.

The bigger tires definitely change the overall gearing and definitely reduce engine exhaust braking by the VNT. The only question is how much and is the op feeling the change.

 

[EdGarcia]

Harvey... you are correct. I have done absolutely no modifications at all to my new truck, except for the new tires. I even used the stock rims.



As mentioned earlier... I am taking my rig in tomorrow for the scheduled 15k service + oil change. While there, I'm going to mention this to the techs and have them inspect the exhaust brake, switch or whatever needs to be looked at.



Hopefully, they will have an answer... emphasis on hopefully.



Ed

 

[EdGarcia]

Well, here's an update on my recent visit to the dealers. They told me my exhaust brake was working as meant to. I don't buy it... it is not working like it was the first 11 months I've owned this truck. I'm going to do some research on this issue and keep you folks posted.

 

[Bob4x4]

265's are 658 31. 7"
285's are 635 32. 3''