48RE 3rd Gear Lockup ?

[DWestfall]

My friends 2003 HO goes into lock up at 2000 RPM in 3rd. Letting off the accelerator it unlocks immediately under 2000 RPM Under 50. The problem he has is that when towing a load at 45 MPH the transmission unlocks and he can watch his transmission temp rise. My 47 re will stay locked up all the way down to 40 MPH. Is this normal for a 48 RE? He only has 35k on it. Any help is appreciated. Thank You.

 

[bagd99dak]

my 05 with 48re only locks up 4th. however in tow/haul mode it will lock up in 3rd as well. when excelerating it locks up around 40mph. when coasting it will stay locked up down to 30-35 mph.

 

[BHolm]

Has he tried running with the "O/D off" button engaged? Maybe that will get the convertor to stay locked? Otherwise, depending on the load, he may be using too much throttle for the convertor to stay locked and the trans is trying not to lug the engine, which can produce high egts.

 

[DWestfall]

48re 3rd gear lockup?

His TQ unlocks even with the O/D button set to od off (under 50mph) and the truck coasting, empty. My friend's TQ will stay locked up in 4th, coasting or working under load (light throttle) down to about 45mph, but in tow/haul 3rd gear it will not stay locked up when coasting under 2000 rpm. It has done this since day one, but only a bother when towing a load under 50mph

 

[PGreenleaf]

Thats normal for the 03 to function like that. 04s function the same way . Its a 4th gear lockout. In normal mode TC locks in 4th . With 4th locked out TC locks in third. But when trottle is let up TC unlocks . 05 is a total different setup. 05 has NO 4th lockout. But is capable of 2nd ,3rd, and 4th gear TC lockup in tow haul mode. Also has TC lockup for downhill motor brakeing in 4th,-3rd, and 2nd. 06 is the most desirable so far. 06 has 3 modes -normal- tow haul- and 4th lockout. My 06 appears to go into TC lockup in 2nd gear when accelerating in tow haul with load And stays locked through 3rd and into 4th. Works great. Also downshifts by self for downhill motor brakeing through 3rd and 2nd with TC locked.

 

[Tinman]

What the 06 doesn't do is keep the TC locked in O/D lockout like it does in tow/haul. This drives me crazy since I prefer to drive with overdrive locked out a lot. But I can't stand the unlocking of the TC in 3rd O/D off. TC lockup in Tow/haul is great, but it will shifts into 4th at about 47mph. So, does anyone have any idea if there is a way to lockout 4th in tow/haul? I was trying to figure out if I could put a toggle switch in the O/D lockout circuit but I am not having any luck thus far.

 

[FDrake]

lockup?

Maybe I misunderstand the Tow/Haul switch. I thought it was to keep the transmission unlocked when towing. Mine drops out of OD when I engage it. Am I wrong? Is the transmission locked up then? I wasn't sure.



Also, I have read numerous times about the "mystery switch" and the need to be sure it is off when you stop. Has any one tried to use a "momentary" switch for that so the switch is normally off? That way it will cause the transmission to lock up but will allow it to release since it is normally OPEN. Once the transmission is locked, will it remain locked while under pressure?

Frank

 

[PGreenleaf]

Maybe I misunderstand the Tow/Haul switch. I thought it was to keep the transmission unlocked when towing. Mine drops out of OD when I engage it. Am I wrong? Is the transmission locked up then? I wasn't sure.



Also, I have read numerous times about the "mystery switch" and the need to be sure it is off when you stop. Has any one tried to use a "momentary" switch for that so the switch is normally off? That way it will cause the transmission to lock up but will allow it to release since it is normally OPEN. Once the transmission is locked, will it remain locked while under pressure?

Frank

If you got a 04 Drake, your switch reading is decieving. You dont have tow haul as it states. You push your button you lockout 4th just like all the older diesels. Your trans will downshift to 3rd and then go into 3rd TC lockup.

 

[FDrake]

I thought so.............

PGreenleaf,

Thats what it feels like so I thought I would ask. It does retard when towing as I wanted it to do. If I set the cruise control and go downhill, the transmission DOES downshift to help slow me down without the Tow/Hual pushed in. But as soon as I hit the brakes to slow down more, it disengages the cruise, so I need to reset it each time. I guess it works as designed so I will not worry over it. Thanks for the input.

Frank