I have a 1991 F250 with an M5OD manual in it, and as far as I know it is running a standard ATF (just bought it). I would like to switch to a synthetic, probably Redline D4, or MTL. What I am concerned about is that there are 112,000 miles on the truck and I wonder if switching to synthetic could pose any problems with seals leaking. Any help is greatly appreciated!

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1991 F250 R/C L/B 4X2
300 I6 5 speed

 

Synthetic fluids do not "cause" leaks. This doesn't refer to previous leaks. If it's the recommended type, it has to meet the same specifications. Good Luck !!

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2000 F-150 XL, RC, LB, 5.4L, 4R70W, 3.55LS,
Class III tow, Payload #3, & Convenience pkgs.,
4-wheel disc/ABS, Chestnut/Parchment 40/60,
Ford bedliner w/Paintsaver & gas/wheel/spare locks,
K&N F.I.P.K. w/Outwears pre-filter, Superchip,
Dynomax ultra-flow welded 3" cat-back w/ 3" Y-pipe,
Hellwig front & rear anti-sway bars, Rancho RS 9000s,
Mobil 1, K&N oil filter.

 

I just bought a 1990 f150 w/ a M5OD tranny.
Do you know anything about these trannys? Are they good/dependable?
Mine has 132k and I just changed the fluid in mine.

Except for a little grinding from 2nd to 3rd, and a REALLY REALLY low geared 1st, (can't even get to 15mph w/o almost reline the motor) the tranny seems to be great.

Your thoughts/comments are welcome.

 

HI
The M50D tranny does not use ATF. It uses gear oil just like the rear axle uses 90w-120w. The first gear is a compound or better known as a "granny" It is extremely low. The gear oil in a manual transmission is for lubrication only. Not like a auto tranny which ATF not only lubricates but actually runs the tranny. You really don't need to change it, just make sure the level is up.

 

I guess I'll have to beg to differ with Lane. My owners manual says ATF for my M5OD. I can't speak for a 1990 model though.

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1999 XLT SC, bright red, 4.2l, 5 speed, MAAP stainless nerfs, Prime Designs bug deflector, Astro Euro-Lid II, Mobil 1 Synthetic Oil and Transmission Fluid. Check it out at:
http://www.ownersite.com/OwnersitePu...fm?veh_id=3415

 

Thanks for the help guys!

I DO know that the M5OD transmission takes ATF, it always has. I've checked the Ford shop manuals and the recommended refill fluid is ATF, it has been since the trans was introduced in 88. The reason I was thinking of using synthetic is that everybody says that it makes for a slicker shift, and it also would probably provide some added protection. Thanks again for the advice!

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1991 F250 R/C L/B 4X2
300 I6 5 speed

 

Tye,
Does your tranny seem to have a granny first gear?

Do you ever have any trouble with it grinding a little going from 2nd to 3rd?

Thanks,
James

1990 F 150
300 I6
5spd Tranny.

 

No complaints here. 92' F150 4x4 with 260K on original trans. I've replaced the shift forks and put a seal on the output shaft. Also put in a new clutch and slave cylinder at 180K. I've pulled everything from 5000 lbs of sod to a 5700 lb Bobcat. M5OD is light, easy to lift for replacing the clutch and small enough to work around. My only complaint is the worthless clutch I got from FORD, all their clutches are remanufactured. Next time I'll go with a Centerforce.

 

The M5OD does not have a granny gear and does not take gear lube. This tranny has been around for 25 yrs and has always used ATF. Synthetic works great and will improve shifting.

 

I use gm syncromesh in my m5od. It works great in them. The atf used by the factory just didn't cut the mustard.
Alan

 

.........does great for me. Switched over to it the first weekend I got it in Sep. '96, and not a problem since.