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#54040 12/27/2005 3:32 AM | Joined: Sep 2003 Posts: 343 Member | | Member Joined: Sep 2003 Posts: 343 | I will be rebuilding my SM420 4-speed transmission very soon and I would like to get some opinions about what oil I should use in it when it's rebuilt. The Novak site where I ordered my rebuild kit recommends a type GL-4 rated oil from Stalube or Redline, but they do not specify the visosity rating or how much I will need. Does anyone recommend any particular brand and viscosity? How many quarts will I need for my freshly rebuilt SM420? I found a place selling Redline MT90 Manual Transmission Fluid, which is a 75W90 GL-4 for $8.95 a quart. http://www.turnermotorsport.com/html/detail.asp?PRODUCT_ID=MT90 The 1954 service manual states that a SAE 50 oil should be used. Any thoughts? Thanks. Jim
1954 GMC 1/2-ton Longbed
1971 Pontiac LeMans Sport
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#54041 12/27/2005 3:56 AM | Joined: Jul 2004 Posts: 5,708 'Bolter | | 'Bolter Joined: Jul 2004 Posts: 5,708 | cujo,
justferyerinfo...SAE 50 motor oil is the equivalent of a AGMA 90 wt gear lube. The Redline 75W90 sounds like the cats meow to me..pour it in till it pours out!
Stuart | | |
#54042 12/27/2005 4:14 AM | Joined: Sep 2003 Posts: 343 Member | | Member Joined: Sep 2003 Posts: 343 | Thanks atomarc. Do you have any idea how many quarts I will need for a SM420?
1954 GMC 1/2-ton Longbed
1971 Pontiac LeMans Sport
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#54043 12/27/2005 4:26 AM | Joined: Sep 2003 Posts: 343 Member | | Member Joined: Sep 2003 Posts: 343 | Redline also offers a MTL manual transmission fluid that is a 75W/80W GL-4 gear oil.
automarc do you think that MT-90 is better for my application than the MTL?
I feel I am definitely going to go with one of Redlines manual transmission gear oils from the reading I have done on other forums.
1954 GMC 1/2-ton Longbed
1971 Pontiac LeMans Sport
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#54044 12/27/2005 5:12 AM | Joined: Jul 2004 Posts: 5,708 'Bolter | | 'Bolter Joined: Jul 2004 Posts: 5,708 | cujo8, Mr. Google tells me your transmission takes 5 1/2 pints of gear lube. The Redline site states the MT 90, being a 75W/80 is a tad heavier than the MTL product. Your 5.5 pints would equal 2.75 quarts. I would opt for the heavier one...this ain't no BMW with fine German tolerances!  Stuart | | |
#54045 12/27/2005 2:56 PM | Joined: Sep 2003 Posts: 343 Member | | Member Joined: Sep 2003 Posts: 343 | Thanks Stuart! You have been very helpful.
Jim
1954 GMC 1/2-ton Longbed
1971 Pontiac LeMans Sport
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#54046 12/28/2005 12:25 AM | Joined: Jul 2005 Posts: 2,031 Shop Shark | | Shop Shark Joined: Jul 2005 Posts: 2,031 | My .02
My rear-end (inliner) says for me NOT to use any Stalub products. He's seen the inside of more rear ends than I care to think of and been doing that for 28yrs.
Period
I thought stalube was good, but I don't know 1/4 of what he has forgotten.
Jim & Caroline
The highway is for gamblers, better use your good sense."
Gooday-that's my 1¢ answer due to the lousy economy ~ cause I ain't got - no . mo . doe
Every Shaver | Now Can Snore | Six More Minutes | Than Before ... | Half A Pound for Half a Dollar | Spread On Thin | Above the Collar || BURMA-SHAVE
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#54047 12/28/2005 12:38 AM | Joined: Jul 2004 Posts: 5,708 'Bolter | | 'Bolter Joined: Jul 2004 Posts: 5,708 | Jim, I won't cast dispersions on your mechanic..but if he has been doing it for 28 years and Sta-lube has been kicking around for 28 years too, I would say that means something. I have never attended a board meeting at a major oil company gathering, but I can't imagine they sit around and say " how can we build and sell a inferior product". There are lots of myths out there, especially about oils and greases.  Stuart | | |
#54048 12/28/2005 12:44 AM | Joined: Oct 2001 Posts: 3,458 Extreme Gabster | | Extreme Gabster Joined: Oct 2001 Posts: 3,458 | 50 weight motor oil and 90 weight gear oil are the same viscousity.
I use 85w90 in my SM420, works fine, runs quiet, doesn't leak. GL-4 or GL-5 are fine, just don't use hypoid gear lube or it will eat up the synchros.
Paint & Body Shop moderator
A lone amateur built the Ark. A large group of professionals built the Titanic. | | |
#54049 12/28/2005 3:39 AM | Joined: Jul 2004 Posts: 5,708 'Bolter | | 'Bolter Joined: Jul 2004 Posts: 5,708 | 4ontheFloor, My limited lubrication experience has been with Standard Oil Co. They made about 6 different gear lubes for transmissions and rear ends. All but one were classified "for hypoid use" and were recommended for every standard transmission made since the dawn of time. There is no additive in these lubricants that will "eat up a synchro". I would guess if you looked at the spec sheet for the 85w/90 gear lube you are using, somewhere you would find a notation approving it for use in automotive rear ends..hypoid gears. I think this is one of the pesky myths!  Stuart | | |
#54050 12/28/2005 3:53 AM | Joined: Feb 2002 Posts: 2,893 Socket Breaker | | Socket Breaker Joined: Feb 2002 Posts: 2,893 | cujo8, check this out: ----- this text taken from the following URL --- http://www.novak-adapt.com/knowledge/sm420.htm When refilling your 420 with gear oil, choose a GL-4 rated oil instead of GL-5. The latter has a higher sulphur content that is mildly corrosive to the bronze alloy synchros of the this and many other transmissions that do not have composite synchronizers. StaLube and RedLine are brands to look for, among others. We recommend that you select a conventional lubricant or a para-synthetic in lieu of the full synthetics. --- the above text is from the above URL at Novak Adapters website --- If those guys don't know.. then it isn't to be known. Other good info. about the 420 there also... hope this helps... -W | | |
#54051 12/28/2005 4:17 AM | Joined: Feb 2002 Posts: 12,029 Cruising in the Passing Lane | | Cruising in the Passing Lane Joined: Feb 2002 Posts: 12,029 | Stuart, Josiah - "hypoid" is a term used interchangeably w/ "EP" or 'extreme pressure' and has to do w/ the cut of the gears , sort of curved for gradual meshing, so require oil additives that work against 'sliding' - 'non-hypoid' are the straight, square cut gears that mesh much more 'harshly' - it's the rear [ring/pinion] that are normally hypoid, trans gears aren't the problem w/ hypoid rated oils in the trans is they defeat the friction needed by the sliding syncros to work properly - so I'm told  maybe as Novak sez the additives in hypoid oild are more sulpherous as well Bill | | |
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