Cold shift problem

[mazdab40004x4]

I dropped this on the Official A4LD Problems thread last week, but since I didn't get any response I figured I'd try a fresh post.

I have a 1994 Mazda B4000 (4.0 V6 with A4LD and 4x4) with a problem shifting when cold. It drops into gear (forward and reverse) just fine when first started. But it will not shift from first to second gear when cold unless I manually start in 1 and shift up to 2. Once I shift manually a handful of times through the gears and the engine warms up a bit, things will work OK if I drop it into D. Fluid looks perfect -- the right amount, the right color, and not burnt. Any ideas? It's been freezing down here in GA the past few weeks and its a pain in the rear to shift the darn thing manually!

I just bought this truck a few weeks ago and don't know any history on it. It's got at least 240,000 on it but the odometer is busted so I don't know exactly. Looks like it's had 'some' work done on the tranny and 4WD before -- it has a relatively new pan on there and some interesting wiring on the transfer case motor. But both seem to work OK when things warm up.

Thanks for your help -- Jeff

 

[Earl43P]

http://www.explorerforum.com/forums/showthread.php?t=252142

http://www.explorerforum.com/forums/showthread.php?t=137972

http://www.dolphintransmissions.com/transmission.htm

says "These three components are important in the non-computerized transmissions. They provide the inputs that tell the transmission when to shift. The Governor is connected to the output shaft and regulates hydraulic pressure based on vehicle speed. It accomplishes this using centrifugal force to spin a pair of hinged weights against pull-back springs. As the weights pull further out against the springs, more oil pressure is allowed past the governor to act on the shift valves that are in the valve body which then signal the appropriate shifts.

Of course, vehicle speed is not the only thing that controls when a transmission should shift, the load that the engine is under is also important. The more load you place on the engine, the longer the transmission will hold a gear before shifting to the next one.

There are two types of devices that serve the purpose of monitoring the engine load: the Throttle Cable and the Vacuum Modulator. A transmission will use one or the other but generally not both of these devices. Each works in a different way to monitor engine load.
The Throttle Cable simply monitors the position of the gas pedal through a cable that runs from the gas pedal to the throttle valve in the valve body.
The Vacuum Modulator monitors engine vacuum by a rubber vacuum hose which is connected to the engine. Engine vacuum reacts very accurately to engine load with high vacuum produced when the engine is under light load and diminishing down to zero vacuum when the engine is under a heavy load. The modulator is attached to the outside of the transmission case and has a shaft which passes through the case and attaches to the throttle valve in the valve body. When an engine is under a light load or no load, high vacuum acts on the modulator which moves the throttle valve in one direction to allow the transmission to shift early and soft. As the engine load increases, vacuum is diminished which moves the valve in the other direction causing the transmission to shift later and more firmly."

In your case, I'd try a new Modulator valve (external of trans with a vacuum hose) or clean up the governor (have to remove rear DS and tailshaft). Could still be the valve body or an engine vacuum problem.

Welcome to The Ranger Station!


http://www.explorerforum.com/forums/showthread.php?t=299004&highlight=governor

 

[mazdab40004x4]

Thanks for the reply Earl.

I've been looking through this site and the explorerforum for the last few weeks trying to see if anyone else was seeing this issue. I didn't see any posts that looked exactly the same, but I do remember coming across several that dealt with replacing the vacuum modulator. If I remember -- FRAM had the part that was referenced in a few posts. I went to their site -- and they don't seem to have one listed for the 1994 Mazda B4000. Only the 1995-96. Do you know why? As far as I can tell the 94 Ranger 4.0 is exactly the same as the 94 B4000 -- and that part is listed as OK for the 94 Ranger (FM2336).

 

[strvger]

might try www.lmctruck.com
they have auto tranny modules listed on page 112 of their rbv catalog for model years 1983 thru 1994. however some of their parts numbers do extend on up to 1996 model years. good luck.
and Welcome to TRS !!!!

EDIT: just double checked my catalog and it is the Spring 2010 issue. i'm sure they still have them, but it might be on a different page number now. sorry for the confusion.

 

[Bruce]

Check the vacuum hose and tube from the engine to the modulator, i have seen these get plugged a little bit then condensation gets in there and freezes in cold weather and plugs the vacuum line till it warms up...also might want to change modulator also.

 

[mazdab40004x4]

OK, I've been looking around and I have found a few places that sell a modulator for the 94. So I think I'm good there. Now I just have to figure out the best method to get it changed.

Thanks for the suggestion on the vacuum hose Bruce. What is the best way to clear this line? Compressed air? Or should I just run a new line when I change the modulator? Haven't exactly figured out the route that line takes yet -- it's way too cold to be messing around outside right now.

 

[tonyjklh]

my transmision had the EXACT same problem. wasnt to long before the transmision went out. hopefully the same thing wont happen to you.

 

[mazdab40004x4]

Yes, I am also hopeful that I don't lose the tranny anytime soon -- that would be bad

Hoping to get a look at that modulator this weekend. It's at least supposed to be above freezing. Thanks!