QUESTION FOR CROSLEY

[PeterR]

Question relates to a 2004 460LE when towing.

My feelings are that it is better to tow in third gear rather than OD because it takes the load off the OD planetaries and clutches, also allows the engine to run a little faster.

However, if the convertor does not have lock up in third, then it will continue to churn and pump additional heat into the fluid.

So, the question is, does the convertor ever lock up in third (direct) gear?  I have run in third and definitely cannot feel a lock up and the tach starts to climb with even the tiniest increase in the gas pedal.

If the factory config does not provide this,
is there pressure available to the OD lock up valve when in third,
and if so, would it be feasible to tap into the external harness and activate the solenoid manually.

[Crosley.In.AZ]

I guess you are talking about a 4L60E transmission?

The factory programing has the converter clutch (TCC)  applied in 3rd gear. If you step  on the throttle enough the TCC is released.  Same happens if the brake is applied.


The  2004 strategy on the TCC is a Pulse Width Modulation , so the clutch is actually slipped for smoother application.

Yes; towing in 3rd gear is preferred. The converter should not over heat the fluid in 3rd gear.  Are you having an over heat issue?

Over drive in the 4L60E is a band.  Same band used for 2nd gear.

[PeterR]

I guess you are talking about a 4L60E transmission?

Yes, my late night typo.

Are you having an over heat issue?

So far I have only towed very light trailers that would not exceed 800lb a few miles from the hardware store with this particular car, and never had the slightest problem but I am planning to haul a 2500lb boat about 400miles and as the trans has done 125,000 miles I want to avoid punishing it.

The factory programing has the converter clutch (TCC)  applied in 3rd gear. If you step  on the throttle enough the TCC is released.

That is what I was expecting, however even if I gently feed in the throttle, the engine RPM starts to climb up before the vehicle speed responds suggesting the convertor is open all the time.   Is there any other simple test I can perform.

[Crosley.In.AZ]

Actually seeing an RPM slight jump before speed builds indicates to me the system is cancelling the lockup , then you see a speed increase.  Perhaps I misunderstand your statement?

The PCM detects load increase and will cancel lockup at different rate at different situations.

Is this vehicle equipped with a tow-haul mode?

[PeterR]

Is this vehicle equipped with a tow-haul mode?

No tow-haul mode

Actually seeing an RPM slight jump before speed builds indicates to me the system is cancelling the lockup , then you see a speed increase.  Perhaps I misunderstand your statement?

If the throttle is slowly applied while in third, there a smooth increase in RPM right from the moment the throttle starts to advance, no hesitation then jump as I would expect to see as the converter goes from lock up to open.   It behaves just like an older style trans without a lock-up.

There is a road close by that starts flat then becomes progressively steeper.  I will drive in third with constant throttle and watch if there is a blip in the RPM as the road becomes steeper and the engine starts to labour.

[PeterR]

Fresh test results.
Level freeway with almost no traffic.  
60mph in third gear for about half a mile, then very gently apply more throttle.  
The tach started to climb immediately then speed began to increase

60mph again, then gently lift throttle.  
Tach stared to fall immediately then the vehicle began to slow.

When repeated in OD, the RPM barely moves at first then jumps noticeably.