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| | | | Joined: May 2005 Posts: 227 'Bolter | | 'Bolter Joined: May 2005 Posts: 227 | Hey…
How often should you change the gear oil in your manual transmission and differential?
I am trying to keep track of when to change the GL4 gear oil in my manual transmissions in my 60’s trucks and also the differentials. I tried searching the forms but came up short. I might not be searching for the correct words to bring up this information.
I think time intervals are more important than mileage because these trucks are not at work often and are not my daily drivers. Any help would be greatly appreciated.
Last edited by Bornco; 03/23/2026 4:57 PM.
1960 Chevy Apache (C10)
1965 Chevy C30 Dump Truck
1966 Chevy C30 Tow Truck
| | | | | Joined: May 2015 Posts: 11,134 Housekeeping (Moderator) Making a Stovebolt Bed & Paint and Body Shop Forums | | Housekeeping (Moderator) Making a Stovebolt Bed & Paint and Body Shop Forums Joined: May 2015 Posts: 11,134 | I looked at your posts and didn't find one talking about a previous gear oil change, if that's what you were looking for.
Kevin 1951 Chevy 3100 work truckFollow this saga in Project JournalPhotos 1929 Ford pickup restored from the ground up. | 1929 Ford Special Coupe (First car) Busting rust since the mid-60's If you're smart enough to take it apart, you darn well better be smart enough to put it back together. | | | | | Joined: May 2005 Posts: 227 'Bolter | | 'Bolter Joined: May 2005 Posts: 227 | I looked at your posts and didn't find one talking about a previous gear oil change, if that's what you were looking for. Sorry... I re-worded the question. I need to turn off the AI which keeps changing the wording and read it better before I copy and paste it into the forum...
1960 Chevy Apache (C10)
1965 Chevy C30 Dump Truck
1966 Chevy C30 Tow Truck
| | | | | Joined: May 2015 Posts: 11,134 Housekeeping (Moderator) Making a Stovebolt Bed & Paint and Body Shop Forums | | Housekeeping (Moderator) Making a Stovebolt Bed & Paint and Body Shop Forums Joined: May 2015 Posts: 11,134 | Gear oil doesn't generally wear out, so probably not even necessary to change transmission or differential oil unless they've gotten water in them. My 55.2 service manual says it may be advisable to change if subject to "severe service" but that's not defined and you probably don't use your truck that hard. My modern diesel truck has over 250k miles on it and I have never changed the rear axle lube.
Kevin 1951 Chevy 3100 work truckFollow this saga in Project JournalPhotos 1929 Ford pickup restored from the ground up. | 1929 Ford Special Coupe (First car) Busting rust since the mid-60's If you're smart enough to take it apart, you darn well better be smart enough to put it back together. | | | | | Joined: May 2005 Posts: 227 'Bolter | | 'Bolter Joined: May 2005 Posts: 227 | Thanks!!
I did change the gear oil in my 66 c30 tow truck after a while when I realized they probably drained the trans and pumped back in a mixture of GL5 and GL4 when they rebuilt the PTO and the wrecker shop.
1960 Chevy Apache (C10)
1965 Chevy C30 Dump Truck
1966 Chevy C30 Tow Truck
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