SM465 Leak Help

[tc197]

Hi guys I'm new to the forum and this is my first post.

I have a 1987 GMC V2500 with an SM465 4 speed (3 speed with granny) that is leaking and I'm not sure how to go about fixing it. I've never worked on a transmission before and this is my first standard truck. I've tackled a bunch of problems up to this point (water pump, power steering pump, vacuum leaks, brakes, rotors, front and rear springs, shocks, etc...)  through videos and this site but before I try this I wanted to get a few questions answered and look for some advice.

The leak is a slow drip where after a week I have a small puddle on the ground and I can't tell where it's coming from. I attached a few pictures below and one of my first questions is am I missing two bolts where this plate attached to the transmission?

Will I be dropping the transmission regardless to make any sort of repair?

Thanks for the help and let me know if there's any more information I can provide to clear anything up.

Tom

[zieg85]

Those missing bolts actually hold a brace to some engines.  My 85 V-8 doesn't have them my V-6 in my 86 did have them.

[tc197]

Those missing bolts actually hold a brace to some engines.  My 85 V-8 doesn't have them my V-6 in my 86 did have them.

Ok good to know thanks!

[zieg85]

If your just chasing a leak and not planning a new clutch as well, you may want to degrease it and see if the leak is coming from the side PTO cover plate.  It is much easier to fix if that is all it is

[Burkhalter]

Something else to look is the drain plug. Could it be loose or cross threaded?

[roundhouse]

Id clean it really really good
Then Clean it again  then I'd put some dye in it and use the ultra violet light to see where's it's actually leaking


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[tc197]

Thanks for all the suggestions. I was thinking it wouldnt be the PTO cover or drain plug because it seems to be dripping from a bunch of different places so I was thinking higher up. Does the PTO cover have a gasket inside that can be replaced?

For the dye and UV light, do you know if autozone or any of those places rent out the lights? Or does anyone have a suggested light to buy from amazon or something?

Thanks again for the help!

[roundhouse]

Thanks for all the suggestions. I was thinking it wouldnt be the PTO cover or drain plug because it seems to be dripping from a bunch of different places so I was thinking higher up. Does the PTO cover have a gasket inside that can be replaced?

For the dye and UV light, do you know if autozone or any of those places rent out the lights? Or does anyone have a suggested light to buy from amazon or something?

Thanks again for the help!

The light is just a flashlight

I think I bought the dye and flashlight Ina kit at napa or somewhere

Obviously the light works better at night


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[tc197]

Ok cool Ill search around for the kit. Thanks!

[Irish_Alley]

keep in mind when you drive it around the wind will push the fluid all over, so clean her up and fill it and see if it starts to drip before driving. then if still no drips take it for a short hard drive as to no make much wind but hard enough to spin the fluid all over

[tc197]

keep in mind when you drive it around the wind will push the fluid all over, so clean her up and fill it and see if it starts to drip before driving. then if still no drips take it for a short hard drive as to no make much wind but hard enough to spin the fluid all over

Sounds like a plan. Im gonna find the kit today or tomorrow and hopefully I'll have some news this weekend. Thanks for the help.

[Captain Swampy]

Start with the transmission, but the engines rear main seal  could be leaking into the bell housing.

[tc197]

Start with the transmission, but the engines rear main seal  could be leaking into the bell housing.

I had read about that possibility but I was thinking I'd have drips further forward on the bottom of the motor too. The only other way I've convinced myself it's the transmission is from removing the fill plug and not being able to put my finger in and feel any fluid. I ordered a UV flashlight and dye online so Ill start with that in the transmission and go from there. Thanks!

[tc197]

Dye and light came in but I didnt get a chance to play with them this weekend due to bad weather. Hopefully next weekend will be more promising

[tc197]

Update:

I cleaned and degreased everything yesterday and added some new fluid and dye. Fired it up for 2 minutes and immediately saw where the leak was originating from. On the front of the trans where it meets up with the bell housing is where it was leaking, I believe that's the input shaft seal? I'll add a picture. It also started dripping a little later from the bottom of the bell housing but could that just be the same leak where part of it runs down the inside of the bell housing and part runs down the front of the trans?

Given where the leak is coming from it seems the next step is dropping the trans. My next two questions are:

1. What else should I do while the trans is out. (Ive had the truck for a few months so I dont know any history on when the clutch was done, flywheel, rear main, etc...)

2. Do I attempt this myself in my driveway or have a shop do it? Any thoughts on what it would cost me to take it to a shop?