Manual transmission - oil or gear lube?

douglloyd · Post by **douglloyd** » October 29, 2006, 1:55 pm

Hi,

I am working on a '66 longbed with the Warner T-18 four speed. AFAIK this has never been worked on. I plan to drain about a quart of oil out, then refill it with kerosene. Then you jack up (and securely block) the back end, pull the wheels off, and then run through the gears. This is supposed to loosen up sludge. I have used this trick on an 8N Ford tractor.

The shop manual says 50 weight motor oil, but I've always refilled manual transmissions with 75-90 weight gear lube. Any recommendations? I'm in Tennessee, so heavy lube is not a cold weather problem.

thanks,
Doug

jkimbrel65 · Post by **jkimbrel65** » October 29, 2006, 2:23 pm

I use 80-90w with no problems

Lowell · Post by **Lowell** » October 29, 2006, 2:48 pm

75-90 should do just fine

Post by **Greg D** » October 29, 2006, 3:00 pm

I have used the heavier gear lube up here in the midwest with no cold weather issues. But then you gotta figure a 40+ year old tranny may have a little more clearance in it than a new one.

ICEMAN6166 · Post by **ICEMAN6166** » October 30, 2006, 1:11 am

actually the spec is sae50 in summer, sae 30 in winter.i use sae 40 always, have for years no problems.same in transfer case.got into a bit of a tiff with someone in the quick lube place years ago about that, they were wanting to put gear lube in my trans and t-case, i refused to let them do it, finally got the manager out and they put in the correct stuff.

MadMaxetc · Post by **MadMaxetc** » October 30, 2006, 10:42 pm

both will lube the same.

The heavy stuff will quite it down but will also reduce efficancy.

cdherman · Post by **cdherman** » October 30, 2006, 11:25 pm

You all are going to like this bit of little/seldom known trivia.

Gear oil and engine oil viscosity are rated DIFFERENTLY.

50wt engine oil and 90wt gear oil are actually very similar, in terms of viscosity.

I know, the manual says 50wt engine oil. And that's what's in my t-18. But in the meantime I learned a little more.

Here's a handy chart:

http://www.bobistheoilguy.com/visc.html

Besides -- a T-18 will run on bananna peels or any other lubricant of your choice.

Seriously, as long as you keep a decent modern oil in there, you will be fine.......

Truckfarmer · Post by **Truckfarmer** » October 31, 2006, 5:59 am

I always use synthetic gear lube in the transmission and rearend. I like the lubrication qualities during all 4 seasons and am hopeful that it increase my MPG.

1966 M-100 · Post by **1966 M-100** » April 18, 2009, 3:23 pm

douglloyd wrote:Hi,

I am working on a '66 longbed with the Warner T-18 four speed. AFAIK this has never been worked on. I plan to drain about a quart of oil out, then refill it with kerosene. Then you jack up (and securely block) the back end, pull the wheels off, and then run through the gears. This is supposed to loosen up sludge. I have used this trick on an 8N Ford tractor.

The shop manual says 50 weight motor oil, but I've always refilled manual transmissions with 75-90 weight gear lube. Any recommendations? I'm in Tennessee, so heavy lube is not a cold weather problem.

thanks,
Doug

I want to change the oil in my 66 T-18. How many quarts will it hold? How about the rear end capacity? Can I use the same oil in both? Thx..

slick4x4 · Post by **slick4x4** » April 18, 2009, 7:13 pm

''I plan to drain about a quart of oil out, then refill it with kerosene.''

i have done this to trannys,transfercases,differentials & crankcases...
but i use diesel fuel... a little more lubrication..and about half price
really 'washes' out the 'nasties'

cdherman · Post by **cdherman** » April 18, 2009, 7:45 pm

90wt gear oil and 50 weight engine oil are about the same viscosity. I know it makes no sense, but its true. You should be able to use the same gear oil in both cases

64 f100 · Post by **64 f100** » April 19, 2009, 12:25 pm

I beg to differ on the same , I made th mistake of putting in gear lube instead of oil in my 66 with overdrive. Despite what someone says about viscosity, I now run20w-50 racing oil in my trans. lat winter gave me fits, and I don'tlive the nothern Illinois but on a line with ouisville , Kentucky o a little south of ST. Louis. Last winter with the gear lube, I would ;have to force the tranny in gear at times , and often had to wait for the truck engine to warm the transmission before attempting to move the truck. As far as what will work to lubricate these transmission, I have noticed automatic fluid being used in the later 5 speeds, and this is like putting water in, which may be the reason for the transmission problems these have. I think thirty or 40 wiight should work year round, excepti harsh conditions or very high heat. Few uf us will be using these trucks under harsh conditions daily. Just thought I would add my two cents worth.

Rich

64 f100 · Post by **64 f100** » April 19, 2009, 12:30 pm

Sorry, for the mistakes in my post, should have reread it. With apologize, sorry for not using spell check.

Rich

64 f100 · Post by **64 f100** » April 19, 2009, 12:33 pm

Hah! So much for using spell check somehow it replaced apologies with apologize. I can't win.

Rich

Manual transmission - oil or gear lube?

Manual transmission - oil or gear lube?

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Re: Manual transmission - oil or gear lube?