Hi All ,

I had recently bought a 93 E350 Van with the 7.3 IDI.

I saw some seepage of rear end gear lube from the pinion bearing area so I decided to check the rear end oil level.

I pulled the plug (and it hissed as I removed the plug indicating pressure inside .... isn't there supposed to be a vent or breather somewhere ? Maybe this is causing my pinion bearing area leak (the pressure forcing lube out?) .....

Anyways, I ended up putting in about 1/2 qt of Mobile 1 Synthetic Gear Lube LS 75W-140 (GL 5) because it was recommended by the folks down at the auto parts store.

The lube in the rear end was dark and stained my hands and I probably need to change it but I wanted to make sure I was not running low on lube so just a top off for now

After doing the top off ... I read that I should have used straight 90 wt according to the Haynes manual.

Is using a full Synthetic 75-140 a problem? ... I realize the 75 is lower than the 90 recommended but would the 140 more than make up for it on the hot side? Would a synthetic 75 offer better protection than a conventional 90 or should I try to get closer to the 90 ?

When I do take the time to drain out the rear end I plan on using synthetic for hopefully better protection and increased MPG BUT I cannot seem to find a straight 90 in that .... would 80-90 be OK or go for the 75-140 ? or stick with a conventional 90 if I cannot find it in synthetic ? What would you run ? I don't haul heavy or tow heavy.

probably max cargo at any time is 2000 lbs , max tow 5000 lbs (not at the same time).

Thanks in advance for any and all opinions/ help/

Andrew

 

There’s a vent fitting with a hose running up to a clip on the driver side frame rail. It should be near some brake lines on the axle tube iirc.

I think Ford specs 75-140 for these rear ends, especially if you have a cooler climate. I have 85-140 in mine, and if I were to change it again I think I’d go 75.

 

HI,

Thanks for the info on the venting ... I'll have to look for it ... Hopefully, cleaning that out will keep pressure from building up inside and causing the seepage on the pinion seal area.... Hopefully.

I was worried about the Fluid I put in since the Haynes manual said 90 Weight ....Good to hear that you are running something similar and not having problems / issues.

I guess anything has to be better than what is in it ..... it seems really "dirty"( at least in color) compared to the new fluid.

Thanks

Andrew

 

75w140 is perfectly fine, but id change the fluid sooner than later. Just check to see if you have a limited slip rear-end. The door tag or axle tag will tell you. '3 73' is 3.73:1 gear ratio without limited slip. 3L73 is 3.73:1 ratio with limited slip. If you have limited slip, you need to add the oil suppliment, or buy the gear oil that already has it mixed in.

 

I was watching a YT Video the other night, where the guy was swapping in an
axle with Disk Brakes on it from a newer F250. When he pulled the rubber vent hose
off he noticed the metal fitting that screws in the Diff case was plugged tight with crud.
he used a small drill bit to clean it out.

I guess if you drive in a dusty area, as the Diff heats and cools, dust can be pulled into
the hose and mix with the oil and develop crud to plug it up.

When I drained and filled my 86, the hose was dry rotted, and the plastic plug at the top
was caked up. Replaced the hose and washed the Plastic plug/cap.

Iam using Synthetic gear lube in the Differential, don`t remember what weight.


Charlie