Oil type on a 203 with a part time kit

[ellero]

Ok so one person says 90 weight oil and the other says 30 weight oil. Well when installing it, it was leaking a thick dark grey out the front bottom 2 holes and the oil stoped leaking once it was bolted to the t-case mount and crosmember. That looks like gear oil to me so I am thinking 90 weight was correct.

Well now that its in, I pulled out the lowest bolt in the rear to drain it fully and the oil there and as it drains, it looks to be thinner with a golden color like regular motor oil, so now I am thinking that the 30 weight was correct.

Since my 203 has a part time kit, are there 2 different oil fill and drain areas or is the fill in the rear the only one and all the oil is shared in all parts of the t-case? If it is separate, where is the 2nd fill point and if its the same, what do I use...30 weight or 90 weight? Thanks.

 

[Hogback Fabrication]

80w-90

 

[RaisedK5]

The little oil pump dealy-o inteh tail shaft wont live long on 90w. I ran exactly what the manual(stock) told me to.Straight 30W motor oil. Not 10w30, not gear oil. Straight 30W. Mine lived a long and happy life and gave me no problems untill i chucked half of it for a doubler.

 

[Speedo]

Because of the chain the recommended lube for the 203 was originally the same as you used in your engine, later it was changed to ATF. If you were only using the reduction unit then I would use 75W-90.

Gus

 

[ellero]

Because of the chain the recommended lube for the 203 was originally the same as you used in your engine, later it was changed to ATF. If you were only using the reduction unit then I would use 75W-90.

Gus

What reduction unit? All I know about this thing is that its a 203 with the part time kit. I just put 2 quarts of 80/90 in it from tha last post. The second guy says 30 wt and you say ATF unless I am using the reduction kit. Im confused. Do I need to buy more 80 / 90 or must I drain it again and go 30 wt?

 

[Speedo]

What reduction unit? All I know about this thing is that its a 203 with the part time kit. I just put 2 quarts of 80/90 in it from tha last post. The second guy says 30 wt and you say ATF unless I am using the reduction kit. Im confused. Do I need to buy more 80 / 90 or must I drain it again and go 30 wt?

The front half of the 203 is a 2 speed gear box and it is common to use that section along with a "doubler kit" bolted to a 205 to form a doubler. Since the front half is just gears and no chain it doesn't need the lighter weight lube. In an effort to reduce friction in an attempt to help CAFE standards the OEMs resorted to using lighter weight lubes where they could. You would be fine using engine oil or ATF, your choice.

Gus

 

[RaisedK5]

Forget the doubler,

In 1975 the factory manual stated 30W. Teh reason being, is that the tail shaft bearings are lubricated from a resevoir in the tail shaft by a little spiral oil pump that looks like a speedo gear. Teh Resevoir is filled by splashing by the chain, thats why the instructions with mpst part time kits state to run it in 4 wheel drive for 10-15 mins a month to slpash oil up into the resevoir so the bearings dont dry out. 90w is to thick for the plastic pump gear, or so i've been told. My point is that the Factory manual ( i'll scan the pages if you want) stated 30W that what i ran oin mine and it lived a long happy life, with a part time kit.

 

[RedBrute]

I'm posting this not to start an argument, but a real life case. My son is driving the '79 k10 my dad bought new in '80. My dad always had it serviced at the dealership where he bought it. Before my son went to school in Conn, we put a MM part time kit in it. Imagine my suprise when we did the swap and found the xfer case had 80/90 in it NOT the factory recommended 30wt!!! We reinstalled the 'case and put 80/90 back in it. Son drove it to school in Conn and came home every weekend (500 mile one way) for 6 months until the cost of gas drove him to get an econo-box. My dad drove that truck to Miss, Maine, Maryland and Ill. when he owned it and never had any problems. Truck currently has 190K miles on it. I'd say 80/90 is ok to run especially if you live in warmer climates. Just my .02