Hi guys, I've got an oddball '88 SWB with the M5OD transmission. Since I've had it (about a year now), its always required a lot of gas to get it rolling without it stalling after sitting overnight or during the day at work, especially putting it in reverse for the first time. The shifts have always been a little choppy/jerky/grabby/whatever you want to call it, too. Mostly going into first from a stop, but you can feel it other gears too, especially if you're not flooring it.

Anyway, it seems to have gotten worse and I'm getting to the point where I'm looking at a cause. One thought I had was oil contamination on the clutch discs, I know this will make a clutch feel "grabby". There is some sludge accumulation between the trans and engine, and it appears I may have a very slow leak there.

I have to change the trans fluid this weekend and am wondering if there's anything I should inspect while I'm at it -- I don't know a whole lot about the clutch system on this van and there's next to no information on it. Frankly, I don't even know if its hydraulic or cable, so any information is appreciated.

Thanks!

 

The sludge accumulation between the trans and engine is probably from a leak in the rear engine seal. One of the things that can happen is the leaking oil can get onto the clutch, causing grabby or jerky engagements.

I don't recall if the van uses a hydraulic clutch linkage, but a common problem with that is a leak that prevents the clutch from fully disengaging.

With a cable clutch linkage, sometimes its automatic adjuster can get sloppy, also interfering with disengagement.

 

This is more or less what I was kind of suspecting, but I wasn't sure if it was entirely possible/made sense. I believe it is a hydraulic clutch, but I'm having a hard time finding a good diagram of the clutch setup, I'm assuming because the 5spd/3.0 models were relatively rare. I'll keep digging!

 

You can tell if it's a hydraulic clutch by looking on the firewall to see if you have 2 master cylinders. But since I know that area is pretty tight, so there's probably no space for 2 MC's, I'm guessing it's a cable clutch. Again you can check under the dash by looking to see what's connected to the clutch pedal; a metal rod or a cable.

 

I thought you might be right about it being a cable clutch, because I found the clutch cable, but now I'm reading that the M5OD used an INTERNAL slave clutch... so I'm wondering if that could be causing the problem? I changed the trans fluid (it needed it anyway) and didn't notice much if any improvement.

https://en.wikipedia.org/wiki/Mazda_M5OD_transmission

 

According to docs I saw, your M5OD has a hydraulic clutch. So another cause of hard shifting may be that the hydraulics are leaking, and you cannot fully release the clutch. The leaks usually come from either the master or slave cylinder, as they are the only parts that have moving seals. You can look around the MC at the firewall for wet spots. I'm not sure of the layout of the transmission, but I would also look for fluid leaks around there.

 

The MC looks really rough, but no visible wet spot. One thing I did notice is the MC cap (just replaced last year) was wet around most of the lower lip. Fluid was very sightly down from last top off a week or so ago. I know it's losing fluid but not sure where... Does a wet cap mean anything?

 

Wet cap just means that the gasket in the cap is leaking.

What I would be concerned with is if the level got low enough at some point to allow air to get into the line. If so, the line needs to be bled, or the clutch may not disengage even when you push the pedal to the floor.

 

My thinking too... time to bleed the clutch master cylinder? I'm pretty curious how it's done with an internal slave... Hopefully it's pretty obvious.

 

This is what I show for a 92, I can't go back to 88 for procedure:


Section 08-00: Clutch General Service
1992 Aerostar/Ranger/Explorer Workshop Manual


ADJUSTMENTS

Bleed Procedure



Under normal conditions, disconnecting the clutch coupling will not introduce air into the system. However, if there appears to be air in the system (spongy pedal, or insufficient bearing travel) the system must be bled. The following procedure is used with the hydraulic system installed on the vehicle. The largest portion of bleeding is carried out by gravity.

1. Clean dirt and grease from around the reservoir cap.

1. Remove cap and diaphragm and fill reservoir to the step with Heavy Duty Brake Fluid C6AZ-19542-AA or -BA (ESA-M6C25-A) or equivalent. Brake fluid must be certified to DOT 3 Specification.

1. Loosen bleed screw (located in the slave cylinder body) next the the inlet connection.

1. Fluid will now begin to flow from the master cylinder, down the black tube and into the slave cylinder. NOTE: The reservoir must be kept full at all times to ensure that there will be no additional introduction of air into the system.

1. It should be noted at this point that bubbles will appear at the bleed screw outlet. This means that air is being expelled. When the slave cylinder is full, a steady flow of fluid will come from the slave cylinder outlet. Tighten the bleed screw.

1. Slowly depress clutch pedal to the floor and hold. Loosen bleed screw to allow air and excess fluid to be expelled. Retighten bleed screw when fluid flow stops.

1. Cycle pedal slowly five times with a two second dwell at the top of each stoke.

1. Refill reservoir to level at step. If evidence of air still exists, repeat Steps 6 and 7.

1. The hydraulic system should now be fully bled and should properly release the clutch. Check clutch reserve per the instructions in this section

 

Upper pic: Hydraulic clutch.

Lower (lower) pic: Parts catalog says page 7 for 1988/89 Aerostar, but there is no page 7, so here's 1986/87.

 

Perfect! I think I've got a good handle on what I'm doing now between you guys and the folks over at The Ranger Station. Lots of M5OD info over there. I discovered the clutch master cylinder is indeed tucked up under the cowel in line with the steering wheel more or less. Totally missed it the first time I looked. Doesn't appear to be leaking, or if it is its very very slow. Fluid was maybe down an ounce or two, and I've never topped it off.

 

Just wanted to check back in with an update in case anyone else has issues like this in the future.

First thing I did was change the trans fluid. The old stuff was pretty well used but not terrible... did a minor flush and then a day later realized I used Dex/Merc LV. The shifting, however, was a bit better.

So, then I did the same again with the factory recommended old STP Dex/Merc III a day or two later. The shifting got substantially worse, oddly enough.

I snooped around on The Ranger Station's transmission forum and posted there, and got a helpful reply from a guy that has rebuilt these transmissions to try Redline ATF D4. $50 a jug, but it was a hail Mary and cheaper than a new transmission. Changed the trans fluid again and low and behold, the best shifting yet, but not great.

Now, today I finally got my *** in gear to bleed the clutch. Fluid level was perfect starting off, BUT, I didn't realize the fluid was BLACK. There was actually a lot of sludge build up in the resevoir. I hooked up my homemade bleeder kit and pushed nearly a whole bottle of Dot 3 thru. When I was done you could see a clear line in the 10ft hose where the new, clear fluid was and the old, black fluid was.

I then topped it off and followed the above bleed procedure and lo and behold the clutch feels MUCH lighter, the gear shifts feel MUCH less notchy, the clutch is less "grabby" at low speeds. I got zero grinding, and I didn't have to try 2 or 3 times to get into second on a down shift, either.

So, thank you for all the help, I feel much, much better now. I'm guessing the black sludge was the diaphragm disintigrating over time, so I will be on the hunt for a new cap/diaphragm.

 

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how many 50 dollar jugs did it require?