[Tatertot]

15 Feb 2013

I have a 1998 Caravan with a 3.3V6 and the 41TE transaxle and about 178k miles on the van. Last summer the transmission went out and I got a used one to put in it. I’ve put about 12 thousand miles on it since then, we put about 500 miles a week on it, almost all of which are highway miles.

I try to make a habit of checking all the fluids, but a couple of weeks ago it started acting up, and when I checked the fluid, it was not registering on the stick. I put almost a quart and a half to get it back up to level. So now to the real issue. When we are driving, usually with the cruise control on, the engine surges. Actually, the speedometer drops and the engine RPMs increase to compensate for the speed loss. Only there is no real speed loss. I’ve noticed this more when we are on an incline and it requires more power. It has gotten more frequent and it happens without the cruise control when I hold the throttle steady.

I worry about two things. First is, I have no clue where the fluid went to. I have been watching it like a hawk, and found no leaks and the level has not dropped in the last 600 miles or so. The fluid does not smell burned, but I’m wondering if changing the fluid will help or make a difference.

The second is that while I don’t know all the intricacies of the 41TE, I do know there are two speed sensors, the input and output. It seems I’ve read they caused similar problems for others, and I’m hoping to get some suggestions on what I should do. I see a few options:

1. Pull the sensors out one at a time, clean them off and put them back in, see if that makes a difference.

2. Change the fluid and filter, then clean the sensors.

1. Change the fluid and filter, then swap the sensors from the old transmission.

1. Change the fluid and filter, and purchase a new sensor, or sensors.

You guys really helped me when I swapped the transmission, and I want to thank you all in advance for any advice you may have now.
Thanks. Clay

 

[ImperialCrown]

Definitely change the fluid and filter. Use ATF+4 only. Dropping the pan will give you a look at how much or what kind of debris is at the bottom of the pan. Hopefully the varying tach and speedometer aren't signs of slipping converter or transaxle clutches.
Check the magnetic tips of the speed sensors for iron filings. This can distort the TCM's sense of true input or output speeds.
If you are sure that the fluid loss isn't from an external leak, then check the radiator for a possible ATF cooler leak into the antifreeze?

 

[Tatertot]

I only use ATF +4. Is there an appreciable difference between brands? Say Valvoline?
I'm not sure I understand the difference between the Input and the Output sensors. I have noticed when the cruise control is off and I hold the throttle steady, the speed fluctuates, but not the RPM. Sometimes it is a small drop, from 70 to 60 or so, and sometimes it goes down to 40.

So fluid and filter on the schedule for this weekend. Thanks.

 

[ImperialCrown]

As long as it meets Chrysler MS-9602, it is ATF+4.
http://www.valvoline.com/pdf/atf_+4.pdf
The input speed sensor is next to the dipstick tube. The output speed sensor is the one that drives the speedometer and is the one on the drivers side, front of the transaxle.

 

[Tatertot]

The weather cooperated this weekend, and I got under the van. Dropped the pan and there was a film of very fine stuff on the magnet, but nothing large enough to see as an individual piece. The fluid didn't smell burned but looked just a little off. So I changed the filter and the fluid.
Then I started checking the lines to the cooler, and I found a nick in the one of the lines, so I replaced that as well. The nick was over the output speed sensor, so I took the clip off and cleaned it as well. It had a lot of fluid on and around it. I did not take either of the sensors out. Perhaps I should have, we shall see.

I'm thinking the nick was pretty far forward, and would explain some of the fluid I found on things, that could not have blown there while driving. It leaking while I was driving and perhaps shorting the output sensor or interferring with it, would explain the gauge fluctuation after I had driven 40 miles or so, and then the increased incidents as I drove more.

So I wiped everything down, cleaned things off, replaced the fluid and filter, and the one line. Was going to replace the second line also, but it looked preformed and not just flexible line. So Tuesday when I go back to work, I'll see how it acts on the road, and check for leaks. I didn't see anything in the radiator to suggest an internal leak.

Thanks again.