TC Lock Question

[Giachino]

Guys,



See sig for truck details. When the 3-TC Lock-4 shift occurs (maybe its the TC Lock in 4th?) in the 48re (not in tow/haul), it locks the TC, RMP's drop about 200rpm for a second, then drop several hundred rpm... . I dont remember the first rpm drop happening before? Dont know if I explained this well enough but any thoughts... or can you explain what your's does during the overdrive shift... .



Thanks in advance!

 

[BHolm]

I'll admit I am a little confused by your description but I'll ramble for a minute anyway. It really depends on the conditions. Empty, light throttle acceleration will behave differently than empty moderate accel or hard accel. With T/H off it should go third unlocked, third locked, fourth unlocked, fourth locked. In T/H it will shift third locked to fourth locked. I suspect you are just feeling the locking of the TC. There are so many variables that it is hard to pin it down to a specific shift schedule.

 

[cerberusiam]

The first rpm drop is the shift to OD the second is the TC locking up. The TC locks immediately after the shift so unless you are under a load it is pretty easy to miss events.



Shift lockup for normal mode is: 1-2-3-lock TC-4-lock TC



Shift/lockup for TH mode is: 1-2-lock TC-3-Lock TC-4-Lock TC



Manual shift is the same as TH.



The trans DOES NOT do a locked-to-locked shift. A locked-to-locked shift would be very bad news for a trans that is severely under rated for the engine in front of it. The TC lockup in OD is pretty fast so unless you are listening for it or under a load it is easy to miss.

 

[GaryCarter]

Nope, I'm afraid there is no TC lock in second with the selector in "D", whether you use TH or not. I got that from the service manual.



I have observed that the lock in third is consistent in TH mode.



When not in TH under light throttle there is no lock in third, it goes 1-2-3-4-lock. The 3-4 shift happens and then the TC lock immediately after. This is what the original poster describes.

Under heavier load & throttle, mine will go 1-2-3-lock-4-lock.



Gary

 

[cerberusiam]

Nope, I'm afraid there is no TC lock in second with the selector in "D", whether you use TH or not. I got that from the service manual.

Yep, thats what it says all right. Been told the same thing by several techs also. All sources are still wrong, the TC can and does lock in 2nd in tow/haul.



Furthermore, I highly suspect it is capable of locking in 2nd normal mode also. Remember the discussions a while back about the funky 1-2 2-1 shifts under light throttle? I am thinking what is actually happening is the TC is locking in 2nd and pulling the rpm's low enough the ECU does not like the combination of apps position, rpm, and speed and it kicks the trans back to 1st.



In stock form it is almost impossible to feel the locks and shifts under light throttle. I have 5 months and 24k on the my truck now and it is loosened up a bit. In addition I lost the muffler and have RokTek crank sensor on it. The combination makes it much easier to hear the engine when things happen. There is no SOP feel but the sound changing and the flutter in the tach at the same time is a pretty good indication of what is happening.



There are obvious differences in the 04 and 04. 5 models and it would not surprise me a bit if there are differences in the MY05 ECU's also.

 

[GaryCarter]

Yeah, I would not be at all surprised if different flashes shifted differently.

Ford is notorious for that. They've got as many releases out for their trucks as Microsoft does patches for Windows.



Gary