1990 ranger Major issue I can't resolve


Kash<(")

Forum Member

ASE Certified Tech
Joined
May 19, 2024
Messages
12
Points
101
City
Nevada
Vehicle Year
1990
Engine
4.0 V6
Transmission
Automatic
1990 Ford ranger with a major random issue. 4.0 4WD

First event we were at the boat ramp. I go to pull out of the water and it makes a very fast very ugly grinding sound in rapid a totaling of 3 times in about a 5 second span and puffs out white smoke. Check over everything. No issues found fired it up and drove home.- August 2025

- Went 3 weeks and it did it again switching from reverse to drive in a parking lot. Same nasty grinding sound and puffed out white smoke. Checked over everything and nothing.Drove home. Went and got a transmission flush and inspection. I changed the oil after this also. No concerns in either fluid. - August 2025

- Hasnt made the sound till yesterday. Got my new rims and tires installed and leaving the shop it did it 3 times. I shut down the truck and poped the hood everything checked okay. Refired and it happen to do it with the hood open and smoke rose out from under the intake but it didn't make the sound again after that. Drove it home @75mph.

I have 40k on the newer transmission. Engine mileage unknown. Either 300k-400k or 400k to 500k. It does this issue so fast and so inconsistent I cant figure out how to troubleshoot this. This weekend I'll be changing all the fluid in the truck besides the transmission due to it have 15k miles sense last change. Any ideas.i cannot take it to a shop due to not being able to replicate at all. I'm unsure what triggers this I know we are very slow speed or idling.

Rear diff new fluid and inspection October. New transmission 7-9-24. Transmission inspect and fluid/filter change 8-10-25. Oil change every 5k.

Only thing that hasn't really been inspected or changed is the transfer case but 4x4 works great .This will be looked at this weekend. I daily drive this and I'm a little concerned and confused. Any suggestions. Thanks.
1990 ranger Major issue I can't resolve
 
Check the vacuum hose running from the modulator valve on back of trans up to engine for trans fluid
 
That was good advice.

A busted diaphragm in the modulator lets ATF accumulate in the vac line. When enough gets in there, a big gulp of ATF gets sucked into the intake manifold. That'll make a huge cloud of white smoke.
 

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