48RE TC Lockup in 2nd Gear

[LEerkes]

48RE TC Lockup in 2nd from TSB 18-007-04

OK,



I'm confused. I see threads with people talking about TC lockup in 2nd. My 48RE won't do that. I seem to recall seeing a note in a TSB about adding 2nd gear lockup with a flash, I think it was in the 04. 5 hesitation/white smoke TSB.



Am I correct that the 48RE does not lockup in 2nd but that it can be added through a reflash?



I've talked with my local dealer a couple times, they always tell me they won't perform TSB's unless they see certain codes. I don't have a hesitation problem, guess I could claim poor mileage and white smoke at cold ambient temps - they can't check that until next winter around here.



If I'm correct about the TSB, is 2nd gear lockup available in another TSB?



On edit: Found it again in TSB 18-007-04 - "The new engine controller software also includes a change that allows automatic transmission equipped vehicles to lock the torque converter clutch when a manual 2nd gear downshift is selected. "



Guess I'll go try a manual 2nd gear downshift at lunch today and see what happens. I remember someone saying something about a speed of 27 or 28 MPH.

 

[RankRam]

I have an 03 but I may be able to help.



Do you place the gear selector in 2nd gear? My truck will lockup if I do this. It goes to lockup at around 28mph.



I hope this helps.

 

[LEerkes]

I'll try it at lunch today. I've tried before but don't recall the speed at which I gave up. 28 doesn't seem that quick for 2nd gear so I'm sure I got past that with no lockup. I've also seen other threads with complaints about the lack of 2nd gear lockup in the 48RE.



Did DC change something in the software over the past year?

 

[CIverson]

My 03 locks up in 2nd, but not always if it's cold out and the truck has sat overnight. I think the transmission needs to warm up a bit before it will lock up.

 

[LEerkes]

Nope...

Played with it a bit at lunch today. No lockup in 2nd gear at all, I read the owners manual again (that should be required reading at least once a month for the first 6 months of ownership) and noted that it claims lockup only in 3rd and 4th.



Anybody have a reflash done that gives lockup in 2nd? Does it really matter much... . I do some low speed towing, drag the trailer up some logging roads a few times a year. Steep hills and slow speeds.



Seems like it might be more beneficial going downhill to help slow things down just a little bit more.

 

[Big Rig]

TC lockup in 2nd???

Erk,



I also have an 04. 5, 3500 with 48RE. I do not believe this version of the 48RE has a lockup function in 1st or 2nd.

I went out & tried it a little while ago. The engine was fully warmed up. I started out in 2nd & ran it up to 40 mph. All I got was a high reving engine without the slightest hint of a drop in rpm's suggesting a TC lockup.

Next I went to my owner's manual which also convinced me that we don't have a lockup in 1st or 2nd.

On page 222 it says that the TC engages automatically at calibrated speeds, which doesn't really tell me a whole lot on this question.

On pages 219 & 220 it talks about using 1st & 2nd for going up & decending steep grades. After those instructions there is a note which reads as follows.

NOTE: "Use caution when operating a heavily loaded vehicle in "2" Second or "1" First gear selections in high ambients as torque converter slip can impose significant additional heat load on the cooling system. "

I think the part where it says "torque converter slip" really sums it all up. There is no slip in the TC if it is locked up. Since it is slipping THERE IS NO LOCKUP OF THE TC IN 1ST OR 2ND GEAR.

TC slip builds heat. That is why makers of exhaust brakes make devices to lock the TC to avoid overheating the transmission & shortening its life. Some exhaust brakes are made without the lockup but you are taking a chance of shortening the Trans life.

IMHO this is how it works. I can't speak for the 03's or the 04's, only the 04. 5's. If the 03's & 04's have a different pattern for locking the TC that could explain their seeming better miles per gallon. My TC locks at 50 mph. An earlier lock should provide better milage especially around town.

My . 03 cents worth.



Big Rig

 

[LEerkes]

Big Rig,



I read the same passages today. I think it is interesting that the TSB talks about adding TC lock in 2nd - that is a TSB that applies to 04. 5's. I think it was build dates through early February of '04.



Anybody with the TSB performed on an 04. 5 have TC lockup in 2nd now?

 

[Big Rig]

Where are TSB's???

Erk,



I went looking for the TSB you talked about on this site but their last update to the site was December of 2003, before our 04. 5's were built. Where are you seeing this TSB? I would like to go take a look. Thanks.



Big Rig

 

[XJSuperman]

Mine is an '04 305/555. It locks in 2nd gear.

 

[LEerkes]

Here's at least part of the TSB

Big Rig,



The other thread running on the reflash right now has a link posted by Afacey to what looks to be the first page of the TSB. At least that's all I seem to be able to see.



Here is the link:



http://www.maf.mesanetworks.net/



On the left hand side of that page you'll see a link to the TSB.