48RE + Exhaust Brake: Current Status

[JRG]

Carlton,



I also am not trying to be confrontational, just trying to learn.



As I understand your post, the problems arise when the converter is unlocked, and can't relock itself without throttle input. As I read, the braking H. P. of an exhaust braked Cummins is much grater than a "intake-throttle"(gas) engine. You are the first I have read that has explained "fluid shear". As you explained it I can see how the fluid can build heat, BUT would not that fluid build heat in a gas application even if the gas engines rpm went up to say 1200-1400 rpm. Or would that rpm be enough to circulate the fluid through the cooler? In otherwords if you had two trucks one gas one exhaust braked diesel at the top of a hill and were going the same speed when you let off the throttle, the diesel would slow faster due to the braking H. P. not letting the engine gain any rpm. Although the gas engine would gain some rpm and circulate some fluid eventhough the converter is unlocked in both trucks. This sounds great and would explain why you would have to have the converter locked at all times.



OOPS... one small problem, please correct me if I'm wrong. If I were going down that hill, exhaust brake on, and had my converter unlock due to slow enough speed, my rpms should drop to an idle. Now I am creating fluid shear. If I were to flip off the brake, my rpms would come up and circulate/cool the fluid. Well if my converter is unlocked w/out exhaust brake on my rpms DON'T come up, and how is that any different than having an exhaust brake in the first place?



It seems to me that there is a better argument that the thrust washer problem is due to the extra back pressure ("6x") created when the converter is locked on decel.



As I said before, I can flip my brake on and off with the converter unlocked and see NO DIFFERENCE in the way the engine interacts with the transmission. Fluid shear would happen weather the exhaust brake was on or not. The only possible problem I could conceive would be back pressure against the engine itself, an Cummins has a max already set for that.



PLEASE don't get me wrong, I am just trying to learn and your willingness to respond is VERY much appreciated.



Thank you for your time,



JRG

 

[ACerf]

Exhaust Brake

I am in agreement with the rest of the TDR members. I think DC owes us something for this problem. Once they get the problem figured out they should have a Re-Call making the changes to the transmission! All in favor of this say "I"

 

[Carlton Bale]

Originally posted by JRG

It seems to me that there is a better argument that the thrust washer problem is due to the extra back pressure ("6x") created when the converter is locked on decel.

Yes, you are absolutely correct. The thrust washer wear is due to large reverse torque levels when the converter is locked during braking. This is completely different from the no lockup / fluid overheat condition.

If I were going down that hill, exhaust brake on, and had my converter unlock due to slow enough speed, my rpms should drop to an idle. Now I am creating fluid shear. Well if my converter is unlocked w/out exhaust brake on my rpms DON'T come up, and how is that any different than having an exhaust brake in the first place?

Sorry, I did not explained this very well previously. Obviously, to get the full exhaust brake power, the transmission needs to be in lockup. If it is not trying to lock-up, the RPMs will drop to idle speed and there will be no braking. This is not the condition that is causing overheat. The problem was when MY03 test software was modified to cause lockup during braking, the lockup signal was sent but the trans never locked even though it was trying -- the brake was providing too much reverse torque and that prevented lockup.



The problem was that MY03 vehicles had no way of detecting that actual lockup was achieved. If it wasn't, the fluid overheat condition I described earlier occurred. Because one computer controlled the engine and a different one controlled the transmission, there wasn't any way to detect that lockup was achieved with the brake off before turning it on after lockup.



An ideal situation for the computer controlling everything would be the following:



*Driving in third gear, trans unlocked, engine powered

*Lift the throttle pedal

*Before turning brake on, send lockup signal to transmission because it can't achieve lockup if brake is already on.

*Monitor transmission for lockup

*Once trans is locked, turn brake on



At some point in the future, this feature will be available and will address the "can't relock when brake is on causing overheat" concern. The other concern of the thrust washer will also need to be addressed separately.



Hopefully I've explained the situation a little better this time. Let me know if you have questions.

 

[DPelletier]

Carlton,

That's a pretty good explanation because I think I actually understood it!



Thanks for the information



Dave

 

[JRG]

I. . I. . I. . I. . I. . !!!!!



Carlton,



First off, if I am being a pain please let me know.



I am learning much from your post and I hope others are as well.



You stated that when the converter is unlocked, it can not lock if the brake is engaged due to too much reverse torque.



You stated that the lockup signal was sent when the throttle was lifted ( I am assuming that the 48re has that ability and it might be turned off at the present time) Is this in only 3rd gear or 2nd and 4th as well?



I am not a exhaust brake engineer, but if the aftermarket was able to delay brake engagement until a lockup signal was present would not that go a long way to helping the problem? So in other words the brake would need to see 2 signals, zero throttle, AND converter lockup. If one of those signals is interrupted the brake disengages.

If it is not trying to lock-up, the RPMs will drop to idle speed and there will be no braking. This is not the condition that is causing overheat

If I understand, if the lockup ability was there, the rpms would come up automaticlly and lock the converter if no brake was engaged. It is when the rpms are up with no lockup that causes fluid shear, but if the engine is at an idle it does'n.



If you and others figure out how to make this work, can my ECM/PCM be reprogrammed to work as orig. intended?



Will the 48re be able to "down shift" like the Ford and Chevy trannies can?



Has the thrust washer problem been resolved in the 04. 5 trucks? If not , any idea of how to resolve the problem?



Thanks in advance,



JRG

 

[NC_Mog]

JRG,



If you read Carlton's post, he said that you CAN'T detect a TC lockup via the controlling computer. Yes if you could get a confirmation signal that it had happened, then it would be easy.



Combine that with the issue of the TC not being able to lockup if the brake is engaged, and you have a scenerio of a manufacturer wanting to limit his liability or exposure during everyone's warranty period.



Now I have to ask a question of people wanting a "recall" or have DC answer for this issue... where did it say in the Owner's Manual or sales literature that we could use the auto with an exhaust brake? I'm not talking about a salesman telling you something, but official DC literature. I'm as disappointed as the next guy about not having the ability to use an e-brake on my '03, but no one every promised it to me. I figure once the transmission goes, I'll get an built one capable of handling an e-brake if I use it intelligently.

 

[JRG]

The problem was that MY03 vehicles had no way of detecting that actual lockup was achieved. If it wasn't, the fluid overheat condition I described earlier occurred. Because one computer controlled the engine and a different one controlled the transmission, there wasn't any way to detect that lockup was achieved with the brake off before turning it on after lockup

I admit I did not read careful enough.

Now I have to ask a question of people wanting a "recall" or have DC answer for this issue...

I don't think that DC would answer 100% to this issue. I do think that a truck rated this high should have an exhaust brake out of the box, no assembly required, but you're right nothing is in ink. Do I think that there was at least some deception with the "new better" transmission, maybe.

I will say, that if my fleet mgr. is told something by DC and then relays that to a customer as a "company representative" that is something implied.

Bottom line, if DC did there homework 1st we would be much happier. So now we are left out and the PROPER thing to do would offer your customers some kind of... ... . something. We will just have to wait an see.



P. S. Mogs are cool! Would love to have a set of those axles under my 'cruiser. Keep the greasy side down.



JRG

 

[jrobinson2]

From page 1

Below is the information that was sent to Cummins Distributors. We tried, but couldn't get warranty approval for the MY03. 5 48RE. We will be working hard to get a brake approved for the MY04 or MY04. 5 48RE. I won't be able to give any details on what is changing until after the 04 product is launched but I'll let you know as soon as I can.

Carlton gave us all a big hint something was changing in MY04. 5 (Cummins 600) and nobody even noticed



I remember reading about replacing the thrust washers with bearings in high performance automatic transmissions in the early '80s, I'm sure most of the diesel trans shops have been doing this for some time now.



Jared

 

[Carlton Bale]

Update 5-Feb-2004:

Cummins is still working closely with the 48RE transmission group to make the 48RE compatible with the exhaust brake. One hardware change went into transmission in January and another is planned for February. We are also working on a second round of software changes that require extensive testing. I would like to say that I am confident that this is all that is required to get warranty approval, but I won't make any promises. We've encountered several unexpected issues along the way and there could be more. I'll post as soon as I have more information.

 

[Big MAK]

<top>

 

[thejeepdude]

Originally posted by Carlton Bale

Update 5-Feb-2004:

One hardware change went into transmission in January and another is planned for February. We are also working on a second round of software changes that require extensive testing. I would like to say that I am confident that this is all that is required to get warranty approval, but I won't make any promises.

So... any truck built after February should have the required hardware for the EB and any software changes should be flashable at a later date? Please keep us posted, as I plan to order a truck soon, but wouldn't mind waiting until this is resolved if we're close!

 

[Carlton Bale]

At this point, I would say any truck built after February could have the required hardware for the EB. We may find something else. However, at this point in time, the February trans change and the "later this year" software change are what is planned for compatibility. I'll post as I know more.

 

[klenger]

Even though I am not in the market for a auto/e-brake, it is very refreshing to see a representative of a manufacturer posting accurate information about our trucks. Thank you. You will be rewarded in diesel heaven.

 

[MojaveJoe]

Now that's what I like to hear... something positive for us 48RE owners.



Thanx Carlton and keep us posted.



Regards,

Joe

 

[ACerf]

Exhaust Brake

Food for thought; If you were a company that had transmission problems way back when. Than you brought out a new trans that worked well with engines availble at the time. And than you decided to bring out a bigger and better engine, but you still had the same trans. Wouldn't you think that maybe a new trans that could handle larger HP, and an exhaust brake be a great idea! I think most of us can see the hand writing on the wall! Plus the fact that the other big players have a 5 speed auto behind their diesels! I give DC another year at the most and you will see a new trans. When I talked to a friend of mine that works for DC about this subject he quickly changed the subject, very strange! This is about being the top dog of pickups and to stay top dog you have to beat the other dogs at there own game. The Dodges have the looks and now the braun, but not the brains! Mark my words; Brains are on there way!



Thanks Carlton for all the updates. I am sure that DC will do something. I would not mind having an E-brake but so far I have not really found a big need for it. I have gone down some very steep grades with just the OD off, and never got over 55mph. My fiver weights in at about 11,000lbs with no ill effects of excessive pushing!

 

[RMcCulloch]

Could this have something to do with it?

There's another thread running (this one ) that seems to throw a different light on the Thrust Washer problem.



Could the lubrication problem described in the other thread have any bearing [pun intended ) on the Exhaust Brake issue?

 

[Carlton Bale]

Originally posted by RMcCulloch

There's another thread running (this one ) that seems to throw a different light on the Thrust Washer problem.

I quickly read through the other thread. This is not the same thrust washer; the thread is referring to one that is loaded during positive power, not braking.

 

[FJfonda]

Oh well...

Just got my build date... 2/28. Looks like it'll be a coin toss whether or not the upgrades will be available in time. Going with the auto was a big decision for me and exhaust brake compatibility was an important part of the decision. I'm considering canceling the order and reordering with the 6 speed.

 

[Dean Upson]

If you don't mind the shfting, you will love the NV 5600.



Dean

 

[thejeepdude]

Re: Oh well...

Originally posted by FJfonda

Just got my build date... 2/28. Looks like it'll be a coin toss whether or not the upgrades will be available in time. Going with the auto was a big decision for me and exhaust brake compatibility was an important part of the decision. I'm considering canceling the order and reordering with the 6 speed.

Stick with the auto. The TC sucks anyways, so when you have the TC and VB upgraded, just have them take care of the thrust washer problem at the same time. Then you'll have a rock solid transmission, and no need to row...