Big Dumb Truck
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Thanks rustystud.
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M35a2 oils
- Thread starter Rezdeuce
- Start date
rustystud
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I've been thinking since my last post ( I know, thinking what a concept ! ). It would be very helpful if all the long time users of the M35 truck posted what they have been using in their transmissions and how their transmissions have held up. I know many members use something else besides 80/90w gear oil. So how about it Gimpyrobb, Jatonka, Gringletaube, Warthog, Recovery4X4, Patracy, all you others out there.
Big Dumb Truck
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My M35A2 is new to me. I have only owned it for 5 months now. I've only been driving it for 2 months. My transmission is in bad shape and will be removed from the truck today after work. I know it has gear oil but I don't know what type.
brianp454
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While you have your transmission out can you take a measurement and a couple pictures for me? brianp454@yahoo.com
rustystud
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Actually once you get your transmission out take the top cover off and then take some pictures of the gears and synchro's . This way we can help determine how bad of shape your gear box is in. If it is really toast then you probably would be better off buying a good take out from someone here.
Big Dumb Truck
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This doesn't look so bad to me.
First gear is chewed up.
Some rust on a few parts.
The input shaft has a bit of a wobble to it.
I didn't notice anything else that looked worn out.
rustystud
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Second gear has some severe pitting on it and First gear has some tooth engagement wear also. How long did this truck set without running ? The pitting on the Second gear concerns me. Once the surface hardness has been worn through you will experience rapid tooth wear. I would also check the reverse gear for tooth engagement wear.
Big Dumb Truck
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To keep things on topic I want to say that the wear that I see in this transmission that had gear oil in it is minimal. The rust was most likely caused dy water. The beat up edges on first gear and the reverse gear are from grindind (possibly a synchro) I'm not an expert on this. So over all I would have to say that gear oil worked just fine. On the other hand, I don't know what caused it input shaft bearings to wear out.
I am going to start another thread about my transmission / truck and all of its problems.
I am going to start another thread about my transmission / truck and all of its problems.
Another Ahab
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rustystud, you got eagle eyes; I was thinking the gears were all looking pretty clean:
- Can you maybe mark-up a photo (you know, a red circle or something) to show where you see the pitting/ wear?
rustystud
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I wish I had such skills with the computer, but alas my learning fails short there.
If you look closely you will see at the top of the second gear what looks like small pebbles on the face of the teeth. This is called pitting and it's usually caused by water in the oil. It is actually small holes that have been formed by "exploding" water molecules. When the oil gets super hot from normal driving the water that is in the oil will actually explode when it is compressed against the gears. I know, weird science stuff ! Anyway once the surface hardness is worn off then comes accelerated wear.
rustystud
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Yes the rust was caused by water and also the pitting on second gear. But the tooth engagement wear is caused by slamming the first gear into the reverse idler gear and countershaft gear. This is a NON-synchro gear, so you must shift it when the truck is stopped. Do you know how many miles are on this transmission and gear oil ? and how was this transmission maintained ?
Big Dumb Truck
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I only owned it for 5 months out of 44 years. I don't know what happened before I bought it.
mobileauto2000
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The extreme pressure additives in gear oil have been known to take out the small needle bearings in these transmissions and also affect the synchro operation. That is why the manufacture specifies motor oil. But the truth is most don't get enough miles on them to matter. I have driven my truck 5 day a week for the last three years and it made a huge difference when I switched to 40w motor oil. After a couple months the synchros all started working where before I would have bet money that they were worn out.
rustystud
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I have never heard of any additive that could take out a steel bearing. The needle bearings in this transmission are not that small either. You also never use "engine" oil in a manual gear box. The oil is not recommended for the pressures exerted in a gear box.
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mobileauto2000
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The info on the needle bearings comes from the guy here that makes the taller fifth gear set for these transmissions I can't remember his handle right at the moment. The Motor oil comes from the manufactures own literature. You will find a lot of folks have gone back to 40 or 50w and have seen a large improvement in their transmission operation. I tried but I can't find the link to the documents at this time.
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brianp454
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Any suggestions of a source for synthetic 50w for the transmission (NAPA, Tractor Supply, etc)? I've been looking around and haven't found it.
Big Dumb Truck
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A friend of mine recommend Redline light weight shock proof. He is an incredible mechanic and I trust his opinion.
http://www.redlineoil.com/product.aspx?pid=43&pcid=7
http://www.redlineoil.com/product.aspx?pid=43&pcid=7
V8srfun
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valvoline sells gear oil that does not have a weight advertised I will post a pic of the bottle when I get back to work
welldigger
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Just a warning to everyone wanting all of these super slick oils....your transmission may scratch worse when you shift. The syncros need an oil that has a little resistance to it to slow the gears down so they mesh properly.