So from everything that I've read on here, it seems that after you drain it, you take the side plug out and fill until the fluid reaches the hole and put the plug back in. Just looking at the position of the side plug to the bottom of the trans, there's not a whole lot of fluid going in. The manual says 1.5 pints of fluid should go in, but that's for a 3-speed. It states a 4-speed needs 6 pints. Is there a different way to fill the 4-speeds? I can't see 6 pints going in from this plug....
You can pop out a shifter faster than crawling under the truck and removing the filler-plug, and usually avoid spilling oil when filling from the side. You do have check for the height of the fluid as you near the side plug hole.
Yes,"You do have check for the height of the fluid as you near the side plug hole."
Or, put in the recommended "measured" amount: 6 pints. That amount is still perhaps not "exact" due to the transmission fluid being shared with the enclosed driveshaft u-joint housing/cover (which does not drain, but it usually drips continuously).
I think he was talking about just popping the shifter out and pouring it in the hole. No need to disturb shift forks or transmission cover.
I would suggest that you fill it to 1/2" below the side plug hole. that is the level I fill mine to. The fluid expands as it heats up.
Yes that is what I meant...it would be the only method that would be reasonable, way easier than messing around under the truck. I agree on the 1/2 below the drain plug hole otherwise you may seep gear oil on the clutch when descending steep slopes.
I used about 1 litre or so when I flushed out mine. I removed the side cover/ pto and sprayed all around inside using a parts sprayer. With the drain plug removed and catch pan under to catch flush fluid I was able to analyze the fluid for fillings and debris. With the pto reinstalled I then refilled through the top using about .5 litre more then the recommended amount to a account for the pto the level is about 1/2 inch below the filler plug. FYI I would not use in your kerosene heater with out running through a filter first it was pretty nasty!
Thanks Doyle - Did you try running it at all with the kerosene in it? I've heard that pouring it in and idling for a few minutes will help clean it out. I'm just wondering if a full litre is the right amount for this.
Thanks Doyle - Did you try running it at all with the kerosene in it? I've heard that pouring it in and idling for a few minutes will help clean it out. I'm just wondering if a full litre is the right amount for this.
No I didn't try to run with just kerosene in it, I don't think in my case that was required due to fairly low mileage and I had good access through the pto side of the transmission to spray and flush out the remaining old oil and sludge. I can't really say home much would be required to do this but would assume you would need to fill as per specs, maybe even do it a couple of times.
Sorry, I know this is an old post, but I didn't get around to flushing the tranny last year, so it's on the list for this Spring. I just wanted to see if it was necessary to drop the driveshaft to flush the tranny with kerosene? I just know that I may end up bustin' bolts or something to do this and I'd rather just do a flush for now. I did pop the shifter off last night, so it'll be an easy pour to get the fluids in, which is nice.
I personally think you can flush it in neutral, with the engine running. The clutch gear will be turning-as well as the front mainshaft bearing and clutch housing needle bearings, which turns the counter shaft assembly which in turn turns the front and rear bearings on counter shaft, the constant mesh gears on the main shaft, so second and third gears will be rotating on the main shaft. The only thing not moving is the reverse idler and the first/reverse gear and main shaft as well as the rear main shaft bearing, but they will get washed from the whirlpool going on in there. On 1/2 ton trucks I would not recommend this method on enclosed driveshaft because with no seal in the back other than the driveshaft you will wash fluid down into the rear bell u-joint area.
Last edited by sstock; 03/22/20192:44 PM.
1953 Chevrolet 3100 261 cu inch, sm420, 3.55 rear, torque tube still,omaha orange, still 6 volt, RPO green glass, side carrier spare, all done In the DITY Gallery Video of the 261 running
1964 GMC 1000 305 Big Block V6, sm420, the next cab off restoration
I bet 5 minutes of agitation would be enough to clean it out. Then buy 90 weight mineral oil found at NAPA for about 15 bucks, put 6 pints in and run it for a day or so then drain it out and refill with 6 more pints of the mineral oil. Should be nice and clean then.
1953 Chevrolet 3100 261 cu inch, sm420, 3.55 rear, torque tube still,omaha orange, still 6 volt, RPO green glass, side carrier spare, all done In the DITY Gallery Video of the 261 running
1964 GMC 1000 305 Big Block V6, sm420, the next cab off restoration
Is it really necessary to flush it? I cringe on the idea.
Craig
My '50 Chevy 3100 5 window, '62-235cu, 3:55 rear My truck ....... Respect The Rust If I'm not working on my truck, '65 m00stang or VW camper, I'm fishing with the wife or smoking Salmon.
cmayna - I really have no clue, I don't know what maintenance has ever been done on it. I just want to do what I can to get it performing as good as possible.
Goach, you might remove the pto cover on the driver's side and drain the old stuff out of there and then try and get a popcicle stick and try and reach in and get all the sludge out first before washing. The later sm420s say 61 and newer have a round magnet instead of the chip collector at the bottom of the case. Option B would be buy a complete rebuild kit around $115 disassemble the trans, clean the case properly, replace the 2 bearings on the main shaft, two on the counter shaft, thrust washer next to 2nd gear and synchros on 3rd and 4th if needed and clutch gear needle bearings. They are not that bad to work on but you need a press. You have to get everything removed to get to the Chip collector to remove and clean. I have found on two occasions the retaining ring for the second gear syncro laying in the chip collector all mangled and broken up in pieces. Here is a guy with that problem and doesn't know it yet, but will find his retaining ring in the bottom of his transmission:
Last edited by sstock; 03/25/20192:57 PM.
1953 Chevrolet 3100 261 cu inch, sm420, 3.55 rear, torque tube still,omaha orange, still 6 volt, RPO green glass, side carrier spare, all done In the DITY Gallery Video of the 261 running
1964 GMC 1000 305 Big Block V6, sm420, the next cab off restoration
I do want to do a full gasket change/rebuild on this, just can't put the time in at the moment. I am hoping to get to it with a gear swap next winter, if I can finish up some other projects on the go. I can't go the summer without my truck though
Any reason why a kerosene rinse might be a bad idea?
No cant think how it couldn't but help to clean things up, idling in gear, no load though, wheels up, or idling in neutral like said before
Last edited by sstock; 03/26/20192:19 PM.
1953 Chevrolet 3100 261 cu inch, sm420, 3.55 rear, torque tube still,omaha orange, still 6 volt, RPO green glass, side carrier spare, all done In the DITY Gallery Video of the 261 running
1964 GMC 1000 305 Big Block V6, sm420, the next cab off restoration
1953 Chevrolet 3100 261 cu inch, sm420, 3.55 rear, torque tube still,omaha orange, still 6 volt, RPO green glass, side carrier spare, all done In the DITY Gallery Video of the 261 running
1964 GMC 1000 305 Big Block V6, sm420, the next cab off restoration
So, just cleaning up the area around the drain/fill plugs and before I get too far I wanted to post this pic to see if anyone can tell me where this is leaking (based on the damp areas of grease) and possibly which gaskets will need to be replaced. I'm not quite ready to drop it and rebuild, but I'd like to get my supplies ready for when I do. https://photos.app.goo.gl/GaRto8NiLbutUKR79
Couldn't open px, however here are only a few places besides the top: input shaft, rear seal, front retainer bolts loose, drain plug of course, crack in case-very unlikely.
Ed
'37 GMC T-18 w/ DD 4-53T, RTO-610, 6231 aux., '95 GMC running gear, full disc brakes, power steering, 22.5 wheels and tires. '47 GMC 1 ton w/ 302, NP-540, 4wd, full width Blazer front axle. '54 GMC 630 w/ 503 gasser, 5 speed, ex fire truck, shortened WB 4', install 8' bed. '55 GMC 370 w/270, 420 4 speed, grain, dump bed truck from ND. Works OK.
I dont think I have ever seen a trans this dirty,lol. I would knock some of that grease and crud off of it first before cleaning the inside. There are 5 gaskets on this trans, the top loader, the front bearing retainer, which you cant get to unless you remove the trans. The rear bearing retainer, which you can replace if you remove the rear ujoint housing and u joint, this one is what is leaking by the looks of it. The PTO cover is the 4th gasket. The fifth is between the rear bearing retainer bell and the mounting retainer of the universal ball. There is a cork seal on the universal ball and slip joint bell flange at the rear of the ujoint as well as a small cork seal on the small end next to the torque tube. Knock some dirt off of it and it will come into focus better.
1953 Chevrolet 3100 261 cu inch, sm420, 3.55 rear, torque tube still,omaha orange, still 6 volt, RPO green glass, side carrier spare, all done In the DITY Gallery Video of the 261 running
1964 GMC 1000 305 Big Block V6, sm420, the next cab off restoration
1953 Chevrolet 3100 261 cu inch, sm420, 3.55 rear, torque tube still,omaha orange, still 6 volt, RPO green glass, side carrier spare, all done In the DITY Gallery Video of the 261 running
1964 GMC 1000 305 Big Block V6, sm420, the next cab off restoration
I'm going to bring life back to this thread, since it's mine anyway
I have two SM420's, one that's in and original to my '48 and one that came out of a 56ish truck. I'm looking to go through and refresh one when I do an engine upgrade.
Question is, how to determine which one is in the best-shape to use?
Well, you know how the one you are using, so you will know what parts to replace, synchros are the biggest wear items that are hard to determine wear on. Shafts are easily inspected, bearings are cheap and easy to replace.
Ed
'37 GMC T-18 w/ DD 4-53T, RTO-610, 6231 aux., '95 GMC running gear, full disc brakes, power steering, 22.5 wheels and tires. '47 GMC 1 ton w/ 302, NP-540, 4wd, full width Blazer front axle. '54 GMC 630 w/ 503 gasser, 5 speed, ex fire truck, shortened WB 4', install 8' bed. '55 GMC 370 w/270, 420 4 speed, grain, dump bed truck from ND. Works OK.
