my 99 f150 with the v6 4.2l has 151,083 km on it . and i was wondering at what milage i should drain the transmission fluid and replace the filter? and what milage i should drain the rear axle oil? or can i go a few more miles on the truck without worrying about it. I love the truck so i am just looking out for the ol girl .thanks all i really appreciate the help and suggestions from this site.

 

Don't worry about the rear, but the tranny should be done like now (assuming it's an automatic).

 

Ok - to put this in terms I understand - a bit under 100,000 miles.

Suggest to look at the OEM recommended intervals - I would think it's way past due for the transmission service, perhaps a bit past due for the axle.

Of course, there are those that don't do a thing, and the truck continues to run beautifully - I suggest they are the lucky ones.

The OEM has engineers who are paid lots of dollars to figure this stuff out. In order to keep the highest confidence that the truck will perform as best it can for as long as it can, suggest to use the OEM intervals as a maximum suggestion. Fluids and related labor are relatively cheap as compared to failures.

 

Tranny and rear is 30k severe service, 150k normal service. Rear should be fine because the factory fill is full synthetic and there's no way for it to get contaminated - and it can be tricky getting the cover resealed. I don't trust any tranny fluid to 150k.

 

thanks guys for the great info. l guess i will be getting a transmission filter kit and changing the fluid. or can i flush the fluid and then change the filter and check for the right level?

 

Your 99 should have a drain plug in the torque converter so you can do an almost complete fluid replacement without using a flush machine. Drop the pan, drain the converter, change the filter, and refill - it will take about 12 quarts. Use Mercon V spec fluid.

If you want to tackle the rear, buy 75W140 full synthetic, and if it's LS, a bottle of modifier from Ford. I'd advise you to buy the tube of sealer from Ford even though it's expensive - not all silicone sealers will hold without leaking. There's a specific procedure for applying the sealer to the cover, it does not use a conventional gasket.

 

If you want to use a gasket,like I do, FelPro makes one;
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