BSHORT,

You are absolutely right. In Detroit, they make serious design decisions based on cost per unit. They will go to great lengths to save $.50 per unit because when you multiply that by a million units, you're talking about a half million dollars. It would be VERY easy to save millions of dollars per year by holding back a few pints of expensive synthetic axle lubricant from each unit.

Have a great day,
Doc

 

Well, I drove the truck today for the first time since I did the fluidectomy. The transmission shifts MUCH better. I will definitely change the trans and transfer case lube again at the next engine oil change to make sure they are all cleaned out.

Have a great day,
Doc

 

MBDiagMan: My nephew bought a '92 Explorer and he replaced the ATF in the manual tranny and the transfer case with 80W90 gear oil. Reason is that he and his brother have both owned other vehicles with ATF in their manual trannys, and they all failed. They replaced them with good ones from the recycling yard, and they failed too. Found them to be filled with ATF. Replaced them again and changed the oil with 80w90 gear oil and drove them for several more years, sold them, and they're still on the road with gear oil in them.

 

old farmer,

Thanks for the feedback. The problem that I've seen in Texas with heavy lube in a manual transmission is that it builds too much heat. Back in the days when the factory called for 80W90 or basically gearlube, we actually got better service and life by running 50W motor oil in them.

You bring up a great point though. Just like the factory's are running water thin oil in their engines for fuel mileage reasons, it stands to reason that they would be doing the same thing in manual transmissions and transfer cases for the same reason. They are much more concerned with meeting Corporate Average Fuel Economy numbers to avoid fines than they are concerned about longevity IMHO.

I can't see myself moving to 80W90, but I might go to something a little heavier than ATF. I know that Red Line makes a manual trans lube that is supposed to be really good and I think that it is somewhere in the 50W range.

Thanks,
Doc

 

Not being cheap but as easy as that trans is to service I'd think Mercon @ 2.00 per quart and changing it relatively often would win the price vs performance battle compared to using the Redline @ 8 bucks per quart .

Since the trans does not use a filter , the only way to get the wear metal out is by draining .

Even Redline does not promote long intervals because of that fact and it's noted on their website .

It's good stuff though and the MTL is lighter than the MT-90 I use . Dave @ Redline is a gear oil guru extrodinaire and could give you the best recommendation between those two for your trans .

I vote for ATF and change it often ...... just a vote and a FWIW

 

And if only 1% of those axles fail prematurely during warranty period, that will cost them a lot more than they could possibly save since that would cost them several hundred per axle.

BTW, in the service manual they mention foaming and excess heat if the differential is overfilled.

 

aurgathor,

You make great points. That does not mean, however, that they cannot run the axle at a level lower than the bottom of the fill hole without problems. They do make lots of dumb mistakes, but they would not skimp on lubricant if they knew that running it low would lose axles and cost warranty $. It would make lots of sense that they would put less lube in the axle if they knew that it would not cause problems.

That said, this does not confirm that filling it to the bottom of the fill hole is OVER filling.

DOHC,

Your point is also well taken and I agree about changing the lube often, but my transmission and transfer case both have magnetic drain plugs. These go a long ways toward keeping metal from finding its way back to the gears. The good news for lube change interval in a gear box is that there is no combustion going on in there as in an engine. Engine oil changing is necessary due to all the nasty acids and such that quickly accumulate in a crankcase.

I did not know that the Redline MTL is so expensive. I expect I will stay with ATF that being the case. In Mercedes manual transmissions I have had great success using Mobil One 10W30 in them. I have one Mercedes four speed manual with 533,000 miles on Mobil One 10W30 changed every 100,000 miles and the transmission is still excellent. That car is a mid eighties car and during the early years of that series the manual said 10W30 engine oil in the manual transmission and in the last few years of that series the manual said ATF in the manual transmission. That does NOT mean that it would work well in my 4X4, but I wouldn't be surprised if it did work well. Since Ford says Mercon, I will stay with it unless someone like Redline has determined that there is a better alternative.

At this point my plan for the Trans and T/C on this truck are to change them again at the next engine oil change time and then about every 30,000 miles thereafter. If it were a car I would not change nearly so often, but I am doing so in this truck for two reasons; first is that I saw this dark lube come out leading me to believe more frequent changes are warranted and secondly this truck may be subject to getting a little water through the vent from time to time due to the fact that I actually take my 4X4 offroad frequently.

Have a great day guys,
Doc

 

This is from a '95 service manual, page 05-02G-39, in "CHECKING PROCEDURES":
"Lubricant levels are determined by filling the axle 1/4 to 9/16 inch below the bottom of the filler hole with the vehicle in level position."
As far as I can see, everywhere else, they specify an exact amount of lubricant; for example, 5.5 US pints for the 8.8" axle.

 

aurgathor,

Thanks for the info.

Have a great day,
Doc

 

One more thing, upon further reading, this appears to be different for every rear axle listed in the service manual I have. The 10.25" goes up to the bottom of the fill hole, the others are all below the fill hole. I think F150's come with 8.8", and the numbers I quoted are for a '95 8.8" axle.