I have a 1974 ford f100 4x4 with a t18 transmission and im not sure what the transfer case is in it. I am looking too find out what the best oil for this tranny and transfer case would be, it currently has 80-90 in it and has the i refuse too shift when its cold attitude.... factory calls for a 50w motor oil but would like a 15-50 or 15-40 motor oil work better? i heard of somepeople running these and swearing by it or even a lighter 40w for colder weather. but thought i would ask some questions before i change it, and can i run a little atf in with the old 80-90 to help clean it out before i put the new oil in?

 

First I've run a number of manual transmissions but not an 18. That said, I have have had really good luck with Redline MTL as a medium weight lube and "Sycromesh" as a lighter lube. ATF not so much. Also, common GL5 80W-90 is not very good with syncros.

The Redline MTL is a 75W-80 synthetic specifically designed for manuals. As a synthetic, it flows better than 75W dino oil when its really cold and helps shifting at all temnps. I get it from Summit.

The sycromesh is a GM spec MT fluid with viscosity similar to ATF. I get it from the AP store.

In a classic transmission in your situation, I'd try the MTL. The sycromesh would be a little light for warmer weather... but OK for very cold.

 

NP 203 or NP 205, look for a silver and blue tag on the front bottom edge of the xfer case. What does your shift pattern look like? 4L 4H ='s NP 205 gear to gear drive. NP 203 chain drive and sling or slung lubed. You need to figure out what transfer case you have cause they do not take the same fluid.

Offroad Design - Fullsize 4x4 Performance

Here is a good read about it. http://www.bobistheoilguy.com/forums...Number=1610032

 

most definately a 205! has the lock, lo, n, hi, lock

 

Sorry I did not say the left had **** is the NP 203 pattern...find the tag to be sure.

 

ok will check it out when i get home off of work

 

Sothe little blue tag on the bottom is gone but from the pictures u posyed and the shift **** wich seems to be factory as everything else still is on this truck it looks like a 203 chain drive so can I run the 15-50/15-40 oil in both or straight 50/ or 40 or is there somthing different I need to do?

 

If you read the link I posted...everything I read and it makes sense to me, says thinner is better for the 203.

 

just look under your truck, the 203 has the bigger alum casing around the out put shaft,205 has the smaller like the pic's Rich posted above.

 

so everthing in that article says too use a lighter synthetic motor oil or a 75w syn gear oil, seems interesting to me that the lighter oils would work but ill give it a shot it seems too have worked for so manyothers thnx for all the help and input!

 

on another note if i wanted too clean that transfer case out can i drain out a single quart of the current fluid and add a quart of atf for the cleaning detergents or should i just change it and substitute a quart of the new fluid with a quart of atf? or something else that will clean all the old 80-90w out of the gears and syncros in the transfer case and transmission?

 

Personally, I would not worry about a little bit of 80W90 left in the transmission/transfer case. Drain patiently and put the fluid of your choice back in. I don't think a little ATF would hurt the T case, but would never put it into a transmission.

 

ok should i run the truck and drive it for a little bit to warm the fluid up or just shift the t-case into neutral and put it in gear so the fluid warms up and drain it or does it matter?

 

"Best Practice" is to run it and warm it up so any debris gets suspended in the oil then drain it out thoroughly.

 

ok thank you for the info