Ford Ranger 3.0 L 4x4 Manual, brief intermittent grinding noise

Ford Ranger 3.0 Litre Turbodiesel Manual Transmission, 4x4.

Ford Ranger made a single brief spontaneous grinding noise while already engaged in 3rd gear without any action applied to the clutch or gear lever. Vehicle was accelerating up a mild slope.

The same occurrence happened in 5th gear after completing an incline as the slope flattened and I eased off the throttle. Torque was still moderately applied as I heard the same grinding noise twice. No interaction was made with the gear lever and clutch during noise.

Additional information:
I very recently bought the vehicle second hand.
The transmission is patched up with gasket sealant.
Transmission and rear diff oil levels are full, but oil is old.
Vehicle is 4x4.
During idling, a squeaky rubbing noise originates from the bell housing. Noise disappears when slightly disengaging the clutch.
Also consider the grinding noise to come from sources beyond the gearbox.

What could be the cause of the above grinding noise observed during 3rd and 5th gear?

That could be an early sign of a worn out slave cylinder/throw-out bearing.

Tester

Thanks, you’ve got me on the right track with the throwout bearing. I checked out some videos and this confidently explains the squeaky noise during idling coming from the bell housing.

Would a bad slave cylinder cause the brief hard and loud grinding noises when driving at speed? It sounds almost like trying to force the car into gear without using the clutch, though in my case it happens spontaneously.

The grinding noise could possibly be the 4wd hubs trying to lock. I believe they operate on vacuum (they do on some of the newer Ford trucks at least). Cresting the hill would be a low vacuum situation, hubs may operate off vacuum, so that’s what got me thinking that.

Something to investigate, anyway.

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older fords too. like my 2003. when they lose vacuum it tries to go into 4 wheel drive and grind. you would think it should be the opposite. when you lose vacuum it would stay in 2 wheel drive so you do not ruin something. but I guess that would be too smart. but what do I know. lol

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A problematic rear axle shaft end-spline could cause this symptom. Where it mates with the differential side gear. The key to the solution is finding where the noise is coming from. First step, try to figure out a way to determine if the noise is coming from the rear or the front part of the truck.

In the early 1970’s I was a passenger in a station wagon (American car) which had that problem, noticed while on a 300+ mile drive in the middle of Wyoming. We stopped at a shop in a very small town, and the mechanics there figured it out right away. No replacement axle-shaft available locally though. So they pulled the problematic shaft from the differential, and were able to machine/file the splines enough so we could continue the trip. I always wondered how they figured it out so quickly, and were able to do the repair in only about 1 1/2 hours.

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Just some food for thought, but what about the possibility of a rattling exhaust heat shield? Those can come across as grinding.

With a mallet or by wrapping the tail pipe at the outlet in a rag, try whacking the tail pipe and note if you hear anything.

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Thanks for all the suggestions and advice, I’m currently investigating all the possible causes mentioned.

Considering the faulty vacuum locking system, I’ve found the following video that describes the system on my vehicle:

I will check the vacuum and actuator soon.

Considering the damaged spline theory, if the splines were damaged, the amount of torque I could deliver would be limited as the splines would slip above a certain threshold torque, yet I am able to deliver full torque without the grinding noise. I’m still keeping this in mind.

Considering the rattling exhaust noise. It’s hard to describe thr sound I’ve heard. It’s a solid grinding sound that passes through the whole structure of the vehicle. Almost like how you would hear your entire jaw bone/skull vibrating if a dentist would drill your teeth. I’ve heard some bad resonating rattling exhausts before. On my experience it’s different. Yet I will keep this in mind next time I hear the sound.

this is for f-150 but should be the same.

Ford F150 4X4 Diagnosis No Tools Required - YouTube

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This seems helpful, I’ll let you know the results.