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Whiney Mazda transmission in grumbling Ford truck

My 90 F-150 has developped a habit of boiling over the clutch reservoir (losing clutch) when the transmission is overheated. At the start of a recent roadtrip MI to DE and back, I managed to run the trans dry and overheat it. I filled the case at a reststop and went on. 2,500 miles later it is still shifting and pulling nicely, but it makes a loud whine like a DC motor or a bad power steering pump. Have I just burned up the synchronizers, or did I ruin the bearings? How much harder would it be to put in a heavier ZF type trans than to replace the Mazda with a rebuilt unit?

I have never seen a manual transmission over heat and I have owned several and worked on many more. If the transmission oil leaked enough to make the transmission noisy the bearings are shot and it is now toast. If you can find a transmission complete with all the ancillaries that matches your blocks bolt pattern you can do the swap. There may be some details that require some attention but nothing tough.

What “boiled dry” the clutch or the trans? Frankly your description is tough to follow. Did the trans overheat and how did you know? Are you talking about a manual or an autotrans your message really is not clear. The clutch does not “boil Dry” That is a leak if you have a manual trans.

Sorry if my truck is confusing. The mazda 5 speed transmission in my F-150 has a concentric slave cylinder, the hydraulic cylinder which actuates the throwout bearing is mounted around the input shaft of the transmission rather than beside it. When I first overheated the transmission it was overfilled with atf and I was pulling around 7,000lbs of trailer in 5th gear at 65 mph, 4 mistakes at once, but it was pulling so well I couldn’t help myself. When the trans overheated a thick collumn of sweet smoke filled the cab through the then missing shifter boot, followed by the clutch failing, with evidence of dot 3 bubbling out of the clutch master cylinder.

Thanks, that is not the answer I wanted, but it is the answer I need.

Your manual transmission uses ATF and not gear oil? You could also go to a synthetic hydraulic fluid for the clutch with a higher DOT rating.

A 20 year old 1/2 ton P/U pulling a 7000 pound trailer at 65 MPH…Are we having fun yet??

It might be cheaper and easier just to buy a 20 year old 3/4 ton (F-250) which will come with a more robust power-train…Somewhere there will be a Ford Truck forum where the gear-heads will know every possible engine / transmission combination that is possible.

I remember our old International school bus…It had to climb a long, steep hill in second gear and the driver had no mercy for that bus…By the time it got to the top of the hill, gear oil was bubbling up from around the shift lever, stinking up the bus…

A lot of manual transmissions were switching to ATF around 1990. This was an attempt to reduce fuel mileage, since ATF is much thinner than AGL-4 gear lube. I think they were nuts. My wife’s 1990 Mazda Protege with the 5-speed manual was spec’ed for ATF Dextron III or AGL-4. It had ATF in it when I bought it used. I put AGL-4 in it when I changed the lube. I still got 35 MPG (highway) with it.

Transmission is fried. Time to find a replacement.

When Ford decided to use the Mazda transmission with ATF fluid and the hydraulic throwout bearing, the F-150 was off my purchase list. The hydraulic throwout bearing is a maintenance nightmare, and the plastic master cylinder and hydraulic lines are a joke.

To get a better transmission, comb the bone yards for an older F-150 with the more reliable T-5 or Tremec transmission. You may need to compare the flywheel, clutch, hydraulic master and slave cylinder arrangement, transmission mounts and cross member to compare to your truck. You can use the transmission and flywheel for this older truck, provided you replace the transmission seals and resurface the flywheel. I’d use the older truck specs to get a new clutch and new master and slave cylinder. Plan on some cutting and drilling. The master cylinder mounting hole will need to be modified for the new master cylinder. The transmission mount may need to be fabricated to fit the new transmission. And the driveshaft may need to be altered. Be sure to get the older truck driveshaft. The output shaft splines may be different.

I hope this helps.

I’ve never seen a transmission that was spec’ed for both ATF and 90W…That switch would make winter shifting almost impossible.

The heavier gear oil creates MORE friction and would get hotter still…

Sold my dead 20 year old 3/4 carcass to buy this luxury automobile. 98 percent of the time my towing is under 3,000lbs, but I do love trailer brakes and breakaway systems, even if Tand R don’t understand them. The 1/2 ton does let me “feel the road better” and uses less fuel, mostly because I am crawling under it with the engine off instead of idling at the drivethrough.

I tried running 90w in this trans for about 36 hours. Changed the clutch last fall and filled the case, not thinking Ford would call for ATF. I did the work in a warm garage and it drove home like a dream. Next morning the stuff was cold and stalled the engine every time I let out the clutch pedal. Won’t do that again.

Any good way to test a trans in a dead truck? Will disconnecting a U joint and turning the shaft by hand tell me anything? A freind’s grandson just broke three fingers replacing one dead Chevy trans with another dead Chevy trans.

When the cover is removed the shifter hubs/synchronizers, shift forks, shift rails and integrity of the gears and bearings can be checked. If everything looks good and turns smoothly and the hubs engage and disengage smoothly there is a good chance it is in good working order except for overdrive which I believe is in the tail piece. So far I have never been disappointed with a used transmission that passed the internal inspection. I don’t have much faith in any manual overdrive when pulling a heavy load, though.

And, DOT 3 has a boiling point in excess of 400*F. To get the slave cylinder that hot the internal temperature of the transmission would be at the flash point of the oil. And growing up working part time on a farm I have pushed a lot of equipment to the limit. Pick ups, tractors, Mack and IH flat beds, etc. With hay stacked 14 feet high on an IH 2 ton that would not pull beyond 3d in low range the transmission never seemed to overheat after an hour long drive. And I could see the transmission and the ground through the floor. I guess it could have been pushed harder but I don’t know how.

Thanks for the inspection protocol, and since the first misadventure I have been chastised for pulling in overdrive many times, with no explanation as too why this was different, thanks also for clearing this up.

As for the boiling clutch, the transmission oil (ATF) was smoking off the outside of the case as it seeped out, so I had assumed the slave cylinder was boiling. The bubbling out could certainly be due to increased pressure at temp, but not true boiling, or, I may also have some fantastic new problem with the slave cylinder itself. I bought the truck rode hard and put away wet with 165,000 on it, and the parts store guys keep asking why I am restoring a 90. I ran my 77 F-150 a lot harder (though it didn’t have overdrive) and never had any trans trouble, just body cancer. I suspect this truck was lightly built and then subjected to 20 years of extreme abuse, including evidence of the bumper having been torn off and the trailer hitch welded and bolted to the frame.

Thanks again, and I’ll start trolling the local yards this week with a lot more confidence.

Life is short. Move ahead, not backwards…Try to avoid junk-yards as much as possible…It’s very hard to find happiness there.

But I must admit, I did it myself for many years…So Good Luck in your quest!