f 150 noisy 5th gear?

I'm sorry if this doesn't go here, I have always got good info here. I have a 1996 f 150, 302, 5 speed, 4x4. It has 88,000 miles on it. It runs good but when I shift into 5th gear the trans. is very noisy. It is quiet in all the other gears just 5th/over drive. Is this some think to worry about or is this a common problem? I have all ready changed the atf fluid that go in it. I also added a quart of Lucas trans treatment. Is it safe to drive it in 5th gear? Thanks Al

I suspect this is the 5 speed overdrive transmission that is produced by Mazda. We had one in a 1990 Ford pickup truck which was purchased new in 1990. Same set up with a 302 V-8 engine. The slave cylinder for the hydraulic clutch was inside the bell housing around the input shaft, rather than outside the transmission and could be serviced without dropping the transmission. The powertrain warranty did NOT cover the replacement of this slave cylinder. The heavy duty 5 speed with an external slave cylinder, this was covered. Anyway, ours might have had a bit north of 100k on the odometer. The truck was only used for pulling a 4 place snowmobile trailer less than a handful of times, a 16 foot ski boat about the same number of times, and a 20 foot travel trailer 8 times. No distance was any greater than 2 hours away. The fluid was serviced annually. It had started making some noise and shortly after blew out the seals in the transmission, and I think it may have also done the same to some or all of the gaskets. The transmission was removed from the truck. It has been nearly 20 years since that truck left our place, but I distinctly remember the transmission was completely torn down with all new bearings, seals, gaskets, and most likely some other parts. The total bill with labor was nearly $2000. I have been satisfied with most every brand of vehicle I have had from GM, Ford, and Chrysler. This truck had a few minor issues, but using that light duty transmission sourced from Mazda was not a very good idea in my opinion.

I had 2 vehicles, a 1987 Ranger and a 1988 Bronco II, with the 5 speed overdrive transmission built by Mitsubishi that started making noise in OD. Both had a cracked gear in the back of the tranny.

I have one with 400,000+ on it, it rattles and chatters a bit. Always had merc-V in it. It'll probably have kittens now that i talked about it though.

I have a 96 F150 with the 4.9 6 cyl. and the 5 speed. Rolled 233,000 today on it. I don't notice any noise in mine, but now that I say that it will probably start the noise tomorrow.

I've had 2 of these style trannys apart,but a long time ago.5th and rev are in the rear section,if I remember correctly.They are on the same throw on the shift lever,and share a shaft,I believe.So does it make noise in rev,maybe backing up a grade?If it does I would think a common bearing to both,or the shaft, is failing.If only 5th,then possibly the bearing under the gear.Mark

There was a heavy duty 5 speed available in heavier duty trucks. My experience with those? Seemed to be a good durable transmission.

Here is a Wikipedia website on that transmission produced by Mazda:

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