The GMC CCKW

Hi all,

Probably been asked a hundred times before but did a quick search and couldn't find anything.

I'm looking to replace the oil in my diffs on the 353. The manual refers to SAE90 gear oil.

Now am I okay to use a EP90 GL-4 gear oil? I ask because I made an inquiry on a UK supplier who said that the EP90 oil they were selling was not suitable for vintage vehicles as it had additives, but they did stock SAE90 oil.

I thought EP (extreme pressure) was used for Hypoid gears but could be used for non-hypoid gears (don't know if the CCKW has hypoid gears but the jeep diffs use hypoid oil).

Also I understood that GL-5 oils contained additives that could attach bronze? (hence the use of GL-4)

I think the confusing thing is the interchangability of EP, SAE and GL in the oil descriptions.

Thanks

Jon

The newer oils you will find cause leaks.

I have not had a problem in 60k+ miles with the newer oil except leaks...

They are hypoid. If the pinion shaft is below the centerline of the axleshafts, it is a hypoid diff

If you can find it in your part of the world, the Penrite Mild EP is an excellent gear oil for box, t/c, doffs joints etc.
http://www.penriteoil.com.au/products/g ... p_gear_oil

"don't know if the CCKW has hypoid gears"(Jeep Geek)
Yes,both CCKW and Jeep have hipoyd tooth gears in differential.

CCKW with splits is spiral bevel. Note the pinion is even with the centerline of axle

Mine is a Banjo type doctor.I never looked the split(Ford) manual.