The Stovebolt Site Forums The Shop Area Engine Shop Trans. Inspection-What am I looking at?

Muncie 420 (I believe )

Well, I took the plunge and drained my trans. fluid in prep for inspecting my trans. innerds. I ended up breaking the gasket in the process. I planned on replacing it but should have obtained a new one before disassembly. Can I buy these only or will I have to get a whole kit of gaskets?

Well, This came about because I did not like the sound comming from the trans. when I put a strain on it. Even the slightest strain gave me a sort of grinding sound. Maybe 'grinding' is the wrong word here.

I look inside and can't see anything wrong. I seemed to get the proper amount of fluid out when I drained it. I expected to see chunks of metal on the magnet or wear on the gears but I can't see either. Of course I've never seen the inside of a trans. before either. I can post pics if need be but could someone tell me what I should look for or what to do next? Thanks a million.

BTW, I took some pics before I disturbed the magnet too much so I still have the evidence.

ndn, I may see if you'd have some time in the next several days to come take a look. Would that be convenient for you?

Rance

if its an automatic you can buy just the pan gasket but if you got the pan off already you might as well install a filter which will come with a gasket

ooops ok the SM 420s are usually a little noisy after they get old and worn i suspect what your hearing is more like a whining noise which is common to these type trannies after several thousand miles my 63 GMC gets so loud you cant hear the radio if you really strain it lie pulling a 7% grade with 2 1/2 rick of fire wood in the back.if you dont see any loose debris or metal shavings i would just flush it out with kerosene and refill with lube.

and head over to the parts store and get some gasket paper to make yer own

Bill

Sorry I left that out, its a manual, not an automatic. I figured all SM 420's were manuals.

Could it be the bearings I'm hearing? I'm not against rinsing it out and buttoning it back up and 'just driving it'. I just did not want to do damage to something that was 'asking' to be repaired. I'll check w/NAPA for the gasket or just make my own.

Rance

PS: Oh, and what grade fluid should I refill it with? I'm sure the NAPA guy could tell me but I like to ask other folks too.

I bought a gasket kit for my SM420. There was only a couple of gaskets in the kit - one for the side cover and one for the top. I took the side cover off and was glad I did as I found sludge that didn't drain out. I had to scoop it out. With the cover off, you can get to the magnet and clean the shavings off. I believe I refilled it with 80 wt.

Trans. noises are usually in the bearings mostly the front drive brg. If it is noisey in all gears except high that is a real good indication. The front drive gear is easy to inspect. take off the front collar & sray it with a little brake cleaner. Shine a light on it a turn the shaft watching for pits or discolaration on boyh races & balls. It can be replaced without tearing down the trans. but they are not hard to rebuild.

Use 80-90 gear lube in it.

There was a thread here awhile back about adding 20% STP to the 80-90 in the trans and rearend..Did that to mine last week when I changed them both out..Sure made a difference in smoothness and small noises..My 4sp capacity is 6pts, so I added 5pts 80-90, and 1pt STP..Just a thought, Steve

On an old F**d truck I had,I checked the tranny oil sshortly after I started driving it and it was so empty only a pintof gear oil drained out of it,so I put a full can of STP in,and topped it off with 90 wt. It not only made it ALMOST quiet,it shifted easier (4 speeds no syncros),and the rear seal leak slowed to less than half of what it was leaking before.I also put a piece of heater hose on the gearshift from the floor boot to the shift knob;that rid me of a harmonic ringing that bugged me at about 65 mph.
Speed

Broke what gasket,?? did ya take the 6 bolt side cover off ?? thats the PTO cover?? if so...thats a common item, 44 cents at napa... and old 420s arent bad on leaking gaskets,,, a small dab of silicone for a top cover gasket will work even without a gasket,,,or the loctite plastic gasket.. sounds like a bearing noise,,??? if its not jumpin outta any gear its probably not serious...usually if a mainshaft bearing is gone,,,or goin real bad,,,it will be a difinite noise,,,and jump outta gear too...bearings allow the shafts and gears to align and mesh so outta line will make them noisy... the old trick was fillem fulla sawdust and sellem...LOL.. it got sawdust in it..??? LOL...bearings and gaskets are easy to come by for them....gears are hard to find.......new anyway...