Dodge Caravan transmission lock-up - Page 3 - Fuel Economy, Hypermiling, EcoModding News and Forum

Christ · 06-22-2009, 10:17 PM

In the case where you have a pump on the output of the transmission, no.

In the case with almost every automatic transmission since the 60's or so, yes.

Try it for 1/2 a mile or so... you'll either smell fluid burning, or you'll just kill your transmission with no warning.

elhigh · 06-23-2009, 09:12 AM

Quote:

Originally Posted by Southcross

the drawback with Autotransmission-"coasting" (not sure if that is the case any more...) is that the hydraulic pumps only work with the car in drive. Coasting in neutral, the tranny fluid isn't being circulated/cooled and the tranny overheats/burns up.

If the engine is still running, then both ends of the tranny are still turning, so whichever side the lube pump is on, it's still getting the job done.

Some autos you don't dare EOC, but I do engine-on neutral coasting all the time, in every vehicle I drive from a Subie Forester all the way up to a 16ft Fuso cargo van. No worries.

-edit- (reads further in thread) Okay, somebody else said it too. Uh, ditto!

orange4boy · 09-05-2009, 03:47 AM

I'm thinking about installing a TC lockup switch in my Previa. Were would one find the solenoid (It's not in the wiring diagram or Haynes manual I have)

Since I may forget to switch it off, what is the effect of having the TC locked up in gears lower than 3+4? Does it stall out if you try to stop? Why not lock up at lower speeds?

I live in hilly country with a low speed limit and I am hoping that TC lockup will help FE on those steep hills and the flats we do have. I'm always in 2+3 and it rarely locks up.

Christ · 09-05-2009, 04:23 AM

Quote:

Originally Posted by orange4boy

I'm thinking about installing a TC lockup switch in my Previa. Were would one find the solenoid (It's not in the wiring diagram or Haynes manual I have)

Since I may forget to switch it off, what is the effect of having the TC locked up in gears lower than 3+4? Does it stall out if you try to stop? Why not lock up at lower speeds?

I live in hilly country with a low speed limit and I am hoping that TC lockup will help FE on those steep hills and the flats we do have. I'm always in 2+3 and it rarely locks up.

If it's not in the wiring diagram, and you don't have an electronically controlled transmission, it's a fluid circuit inside the transmission. For more information on that, you'd have to contact the mfr of a shift kit for your transmission, who would know a bit more about it than I would.

I just found out the other day that mine isn't controlled by the PCM like I thought it was, so I can't use this idea anyway, unless I modify my valve body to allow for an external valve.

I can't imagine there being a problem with lockup at lower speeds, except if you stop, it will stall you out. (or break/slip the lockup clutch in the TC).

Basically, if you can wire in a switch, you'll have to remember to wire in a circuit so that it's unlocked when you're using the brakes, or after you're below a certain speed, if you were so inclined.

orange4boy · 09-05-2009, 02:37 PM

The repair guide says it's an ECT and there is a an ECT solenoid in the diagram but not specifically a TC lock solenoid. I should look online at another site for a different wiring diagram or ask at a Toyota site. Why don't they set TC lockup at lower speeds and higher loads? My guess is engine knock under high load/low speed.

Thanks for the info. A brake switch is within my current skill set as opposed to a speed sensitive switch.I had also thought of a pressure sensitive throttle switch so it would lock up only under a certain load.

Now that I think about it , my fantastic digital vacuum gauge from Vtec-e, has two output signals which can be set to any vac number. I could set it for on at say, 18 inches so it would be off at idle.

One reason I want to do this is that it would make P+G much more do-able the other reason is the hill climbing issue.

Thanks Christ

Christ · 09-05-2009, 06:10 PM

Selective lockup helps you with engine braking. You probably won't want it on the throttle, as it would then unlock as soon as you let off the accelerator.

I'm not sure why they don't allow it to lock sooner, as other manufacturers more recently have allowed lockup in all gears for faster/smoother acceleration and better economy. I can't see it having anything to do with damage to the clutch, since lower speed = less load on the clutch.

orange4boy · 09-05-2009, 06:34 PM

Quote:

I'm not sure why they don't allow it to lock sooner

Add this to my tinfoil hat theory that cars are built as oil consuming machines.

Christ · 09-05-2009, 06:45 PM

Loosen the neck tie... your hat will fit better :P

At times, I agree... at other times, not so much. It depends on my mood.

micondie · 09-08-2009, 09:31 AM

I agree that you should check for a better wiring diagram. I have the two volume factory set for my Caravan and most of the second book is wiring diagrams. I my case the lockup is accomplished by grounding a lead from the transmission and I will have to wire it so the computer still sees voltage or it will think the solenoid is burnt out and set a code. In Mass I can't pass inspection with the check engine light on. The brake light switch sounds like the best option for unlock but I would suggest a bright RED light as a visual reminder. It shouldn't take long for you to get into the habit of unlocking, when was the last time you forgot to put in the clutch while driving a standard?

orange4boy · 09-08-2009, 12:39 PM

I have now installed an on demand TC lock up switch on my Toyota Previa.

It was simple. For now I have a momentary switch and I will install a parallel toggle and a big red light. In my case, in order to trick the ecu, a 15 ohm, 25w resistor needs to be installed from the ECU TC wire to the ground. I have not done this yet but I don't have to worry about codes.

My thread is here: Freezing the Slushbox. Torque Converter on-demand lockup switch.

Thanks for the thread.