1959 3100 4 speed gear lube weight - The 1947 - Present Chevrolet & GMC Truck Message Board Network

2001convertable · 08-24-2018, 03:55 PM

Hi, I have a 1959 with a 4 speed manual. I think its an sm420. Iam going on a 5 hour trip and wanted to change the gear lube before I leave. I drained it out. All I need to know is the type of lube and quantity. thank you

va4cqd · 08-24-2018, 08:59 PM

75w90
should take 5.5 quarts if completely empty

mikebte · 08-24-2018, 11:00 PM

Can pick it up fairly cheap at a semi repair shop. I get all my transmission and gear oil at truck shops.

**mr48chev** · 08-24-2018, 11:52 PM

85/90 isn't that spendy at the parts house. It takes 6-1/2 pints to fill that trans .

1project2many · 08-25-2018, 08:55 AM

Like many old transmissions, there is no input shaft seal some Muncie SM420 four speeds. The design relies on an oil slinger and LH "thread" on the input shaft to direct oil coming through the input shaft bearing onto the inside of the rear of the bearing retainer. From there oil is expected to drain back into the transmission case through a roughly 5/16" hole below the input shaft bearing. Switching to lighter base gear oil can create a fluid leak where none existed previously. Oil can work its way down the bearing retainer then end up on the flywheel and clutch disc creating a slippery mess and a truck with a slipping clutch. Having tried several different gear oils, multi-viscosity and single viscosity, I settled on 140 wt gear oil in the '57 and in my '36 Plymouth.

08-24-2018, 03:55 PM	#1
2001convertable Registered User Join Date: Dec 2017 Location: wantagh new york Posts: 203	1959 3100 4 speed gear lube weight Hi, I have a 1959 with a 4 speed manual. I think its an sm420. Iam going on a 5 hour trip and wanted to change the gear lube before I leave. I drained it out. All I need to know is the type of lube and quantity. thank you

08-24-2018, 08:59 PM	#2
va4cqd Registered User Join Date: Aug 2008 Location: canada Posts: 87	Re: 1959 3100 4 speed gear lube weight 75w90 should take 5.5 quarts if completely empty

08-24-2018, 11:00 PM	#3
mikebte Registered User Join Date: Oct 2011 Location: Tucson, AZ Posts: 639	Re: 1959 3100 4 speed gear lube weight Can pick it up fairly cheap at a semi repair shop. I get all my transmission and gear oil at truck shops. __________________ 1959 Chevy Apache 3100/ 283 TBI / 4L60E My YouTube: https://www.youtube.com/mikebtte

08-24-2018, 11:52 PM	#4
mr48chev Registered User Join Date: Jul 2007 Location: Toppenish, WA Posts: 15,709	Re: 1959 3100 4 speed gear lube weight 85/90 isn't that spendy at the parts house. It takes 6-1/2 pints to fill that trans . __________________ Founding member of the too many projects, too little time and money club. My ongoing truck projects: 48 Chev 3100 that will run a 292 Six. 71 GMC 2500 that is getting a Cad 500 transplant. 77 C 30 dualie, 454, 4 speed with a 10 foot flatbed and hoist. It does the heavy work and hauls the projects around.

08-25-2018, 08:55 AM	#5
1project2many Registered User Join Date: Mar 2012 Location: Lakes Region NH Posts: 3,200	Re: 1959 3100 4 speed gear lube weight Like many old transmissions, there is no input shaft seal some Muncie SM420 four speeds. The design relies on an oil slinger and LH "thread" on the input shaft to direct oil coming through the input shaft bearing onto the inside of the rear of the bearing retainer. From there oil is expected to drain back into the transmission case through a roughly 5/16" hole below the input shaft bearing. Switching to lighter base gear oil can create a fluid leak where none existed previously. Oil can work its way down the bearing retainer then end up on the flywheel and clutch disc creating a slippery mess and a truck with a slipping clutch. Having tried several different gear oils, multi-viscosity and single viscosity, I settled on 140 wt gear oil in the '57 and in my '36 Plymouth. Last edited by 1project2many; 08-25-2018 at 09:13 AM.



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