Brand: Mazda B4000 shifts hard in lower gears only

  • Article by: PAUL BRAND
  • Updated: August 3, 2013 - 1:00 AM

Q: I have a 1997 Mazda B4000 with the 4.0-liter V6 engine and 5R55E 5-speed electronic transmission. It shifts hard in the lower gears only. I have replaced the valve body separator plate and gaskets and the blow-off solenoid valve. It now shifts better in the higher gears but still shifts hard in the lower gears. It gets worse as the transmission gets hotter. I have installed a cooler and have tried SeaFoam transmission additive with no significant improvement.

A: The Mazda transmission service literature in my ALLDATA database points to several possible causes for harsh shifts, including high idle speed, low fluid level, throttle position sensor (TPS) malfunction, worn transmission oil pump, worn transmission components like the reverse and high clutch, and/or intermediate band and control valve body malfunction.

The idle speed and TPS accuracy are the easiest to check first, so start there. If you don’t find any fault codes or electronic issues, the problem might be in the transmission’s internals. If it is, I think you’ve done everything reasonable and would suggest living with the issue by “breathing” the throttle back just a bit at each anticipated upshift. You might also try manually upshifting the lower gears at low engine rpm to encourage earlier and hopefully softer shifts.

I don’t think major transmission work is warranted until there’s a more significant symptom.

Q: I have a 2009 Ford Ranger with the 4-cylinder engine, automatic transmission, two-wheel drive and no A/C. When I park in the garage and turn it off, for about a minute I hear a sound like an owl hoot coming from under the vehicle. It is intermittent and sometimes seems to be associated with my movements as I get out of the vehicle. Any thoughts?

A: No A/C? A modern vehicle without air conditioning is a real rarity — unless of course it has failed! On a used car lot it would be a “lot queen”— difficult to sell.

The “hoot” sound is likely vacuum bleeding down from something. Primary suspects are the vacuum brake booster and check valve, the HVAC vacuum system. Less likely are emissions-related vacuum components including the EGR vacuum regulator solenoid, vacuum vent valve and manifold pressure/vacuum sensor.

You might be able to pinpoint the source yourself with these two simple tests. After shutting down the engine, wait for the noise to stop, then apply the brake pedal. There should be a “reserve” of vacuum in the brake booster to give you several power-assisted brake applications before the vacuum is “used up” and the pedal gets very hard. If there is no power assist on your first application after the noise has stopped, the leak is likely in the brake booster or check valve. This conceivably could cause a safety issue with a lack of power assist under certain driving situations.

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