koogala

I've seen something like what you're talking about in the Jegs catalog. They have a rather small diesel section in there (3 or 4 pages) It is exactly what you are talking about: a electronic switch that locks up the tc. theres 2 of'em in there they're like 250-300 bucks

bigdav160

I think you're misunderstanding the purpose of the "lock-up" function of the torque converter. Think of the torque converter as two fans (it actually has three). The one fan driven by the engine blows fluid on the other fan connected to the input shaft of the transmission. Since the two fans don't touch you can idle at a stop light without disconnecting the transmission from the engine (ala clutch pedal).

The difference in rpm between the two fans is converted to heat.(the reason for the automatic transmission needing a cooler system) In "overdrive" the potential speed differential between the two fans is so great that A/T fluid would be scorched. So to prevent this the two fans are "locked up". This prevents fluid overheating but doesn't allow "torque multiplication" (the reason for the third fan). All overdrive automatic transmissions need the lock-up function in high gear to reduce fluid heat.

If the torque converter is "locked-up" while coming to a stop the vehicle would stall just like trying to drive a stickshift without touching the clutch pedal. Likewise the torque converter is not locked up while decellerating. It is released.

no_6_oh_no

I don't know if it is a big difference between the 2 but the 06 feels like it has a more aggressive downshift program. My 05 does a lot better than any other truck I have had when it comes to slowing down but without an EB neither of them have what I would call a lot of engine braking. The TH on the 05 seems to be more of a acceleration improver but it works pretty well on deceleration also. Mine will downshift to D and 2nd and lock the converter with no problems. The downshift speeds are lower than I would like but I can override that easily enough. When your in OD and want engine braking just let off the throttle and cycle the TH switch and it should drop into drive and lock the TC almost immediately. As long as you don't touch the throttle it should drop into 2nd and lock the TC at some point also. If I want more braking I just pull it into 2nd and let it slow down on its own. It will initially go to drive and lock the TC then about 47 mph it will drop into 2nd and lock the TC.

As far as flashing the ECU to work like an 06 I wouldn't hold my breath for that. DC doesn't seem to feel the need to support the 05 autos with the EB features. When it gets here I will rejoice but until then the latest version for the ECU doesn't work too bad and coupled with an exhaust brake it will work quite well.

bluesurf

No 6 that is what I was looking for. thanks. I will in the near future be buying an exhaust brake for this truck. I know the 05 are not APPROVED for one but there has to be something you can do. I'm sure pac brake or banks has something. But I was curious as if there was a big difference between 05 06. My cousin owns a tranny shop and I can have the tranny built any which way I wish but it will void my warranty so I was looking for alternatives. My other question is why do they not have more of a lock up feature since it seems to help control loads and saves the tranny if I'm not mistaken. As far as stalling the truck w/tc lock some companies have it unlock once the truck reaches 20mph or so. PLease keep the replies coming as someone might have helpful ideas. Thanks

bigdav160

The 48RE/47Re simply do not have the hydraulic oil available in 1st gear. It is cut off on purpose to prevent stalling in case the solenoid shorted. ( A lesson learned from GM products). Are ya'll sure the torque converter is staying locked up on decelleration? I don't have a DRB 2 or 3 yet so I can't verify. I doubt it is the case as the effect would be subtle on decell. More likely it is the clutches locking up the sprags/roller clutches inside the transmission in tow/haul.

no_6_oh_no

An EB works fine on the 05 trucks as long as you pay attention to what you are doing. Keep the rpm's up while the brake is on and it will be fine. Essentially thats what the 06 setup does is make sure the EB only engages when there is enough pressure to keep things locked and makes sure the downshifts happen when there are enough revs to make pressure. Keep the revs up around 1800-2000 and you should be fine using the EB.

The TV pressure is ECU controlled on the 05's and as long as there is enough speed to warrant it will stay high enough. You can't use the power lok type systems on these trucks to insure high pressure and the ECU doesn't have the cappability to do it but you can manually control it to make things work. The reason DC doesn't want to warranty it on the 05's is too many people don't have the slightest idea how make it work manually and they couldn't get the 05 program to work like it was supposed to automatically.

It doesn't make a lot of sense to lock the TC in 1st as the speed is usually pretty low. In 2nd down to 35 is about all that engine braking is going to any good. Comparing the 47RE and 48RE is about like comparing the TH350 to the TH400. The 48RE has a larger volume pump and heavier parts to handle the TC lock.The only changes for the 06 trans was the addition of programming for the EB otherwise they are the same unit.

I can't speak for other's trucks, but, mine will lock the TC in drive and 2nd on deceleration and acceleration when the TH is engaged or I manually shift it. I have wore out several 46/47 series transmissions that didn't lock up correctly and there is a world of difference between them and the 05 48/RE. Without a locked TC a diesel engine just doesn't provide much braking.

Cheers.

bigdav160

Before I went into the education business I was a 12 year GM Master Transmission Technician. Comparing the TH350 and TH400 is more like comparing a F150 and Toyota Tundra. To the untrained eye they look somewhat alike but no parts interchange. Not even close in their design.

From what I've seen and heard I'll agree. The basic design goes back to the earliest Chrylser automatic transmissions of the 1950's.

You've piqued my interest and I'll certainly find out if it is true but I do not see any purpose in locking the torque converter on decell. Locking the one-way sprag and roller clutches is a must. There can be no engine braking when driving through a one-way clutch. There is a reason the gear selector has "manual ranges". It allows for engine braking by bringing on extra bands and clutches to lock up those one-way clutches.