GMC / Chevy How was this supposed to work?

Kevin B.

Kevin B.

Not often wrong. Never quite right.
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A buddy just got his hands on an 87 K5, diesel. We went for a spin tonight, and it started making this godawful clattering sound. RPM dependant, but it would come and go.

Got back to his place and started crawling around underneath, found some shiny red oil, and then found where the PO had taken an angle grinder and cut open a chunk of the trans housing, right on the flywheel, it looked like to make room for the starter. We figure the tire kicked something up into the trans through that hole, and said something is now rattling around causing havoc.

Maybe the starter is wrong, maybe the tranny is wrong, dunno. My buddy says the PO "suspected something was wrong" with the trans and was willing to replace it if it wasn't up to snuff. So, no harm no foul, I guess.

But ... huh? I'm non-mechanic enough to wonder, is this commonly done? I thought the flywheel mechanism was supposed to stay sealed inside the housing, is it ok to have it exposed to the outside? Or is the ATF we found coming from somewhere else? Does our "rock in the trans" theory hold water?
 
Pics?

The torque converter doesn't necessarily need to be sealed. A lot of transmissions have a removable cover under the bottom 1/3 or so, and you can still drive just fine with that cover missing. It is nice just for protection, but not strictly necessary.
 
No, I didn't get pics. I'll try and be more descriptive - at the very end of the bell housing, upper right corner if you're looking from the rear of the truck, there's a bulge where the starter lines up. I guess the starter didn't fit, because the edges of that bulge in the housing have been cut away. The flywheel is visible through the cutout, and there are empty holes where the trans housing should have bolted to the block.

There's also ATF all under the truck, behind this cutout. I don't know for sure that this is where it's coming from though, by the time we got back it was 1030, and we could only see so much with maglights.
 
its not supposed to be that way, no. I can't remember if the diesels had a different starter or not, but I do know that there is no difference in the transmission cases.

Pocs will be helpful. I will peruse my factory manuals in the meantime. The empty bolt holes could have helped trash the input seal(s), or not. But yeah, there's no reason to have cut the bellhousing like that.
 
Sorry, missed the reply. I'm heading over there tonight, will try and get some pics. It may be a moot point, apparently the PO was willing to replace the tranny if there was any trouble with it.
 
I should know this but I can't for the life of me remember :rolleyes:

I know if you go from a diesel SM465 to a gas NV4500 you have to do some grinding to fit the starter... I can only assume something similar is going on with your friends rig. Does your friends engine have a serpentine belt? That basically separates the early 6.2's from the later models and I think that change was made somewhere in 87. While the bellhousing pattern is the same and all GM V8 transmissions these years are interchangeable I want to say that later diesels used a specific bellhousing with more clearance for the starter. My money is on it having a gas or pre 86 transmission swapped in at some point. This is just a speculation though its been too long for me to remember right now :(

Now why is it leaking ATF?..... Good question :eek2:
 
Couldn't get a decent pic of it with my cell phone. Can't get the lousy pic off my cellphone so I can post it. I suck at the internet. I can text if anyone really wants to see it.

Looking at it again, the gap isn't as large as memory painted it. I'm willing to stipulate that it'd be tricky for a kicked rock to get in there.

The trans is certainly dead, though - the previous owner came to look at it, decided it was a fuel injector making that noise (???) and took it for a drive... they got halfway up the block before the trans blew up. We're going to pull it tomorrow to see what's up, and the PO is looking for a new one.

Got a bit more history - the rig was originally diesel, and converted to gas at some point. We're guessing the existing trans was for the dead gas engine that the PO pulled out, I think you're right on that Rot Box.

I'm gonna say no on the serpentine, just cuz there's a huge hole where the AC compressor belongs. Don't know for sure tho, will check tomorrow.
 
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So, help me out understanding this transmission, cuz I've never even seen the inside of one - doesn't the flywheel need ATF? Does it spin through a pool, or is there a slinger, or does it run dry?

I'm just curious, because it seems like it'd need to be lubricated, but I don't know how you keep ATF in there with a gap between the starter and the bellhousing.
 
There is no flywheel in an automatic. There is a flexplate, and it should never see ATF. :D The flexplate bolts to the crank on one side, and the torque converter on the transmission side. The torque converter has two halves: one side bolted to the flexplate and receiving the engine's torque, the other engaged to the input shaft of the transmission. Engine side starts spinning, turns the transmission side. "Lockup" converters mechanically lock the two halves together at a set rpm--- otherwise, one side is spinning slightly faster than the other and heat is building up. That's why it's important to keep autos cooooooollllll.

The flexplate has no need for lubrication whatsoever. It is there to couple the engine to the torque converter and give the starter something to spin.
 
Ok, good to know. Thanks for the lesson!

Now I'm really confused where the ATF was coming from. Didn't get over there to drop it out today, maybe saturday.
 
It is probably coming from the input seal... maybe the front pump seal, since that's the other thing in the bellhousing. There's not really anywhere else it can leak in the bellhousing. Could also be a leaking tranmission pan, but the difference is easy to spot.
 
Update on this - couple stuck bolts are delaying removing the trans, but there's a front housing that is removeable. The inside is scored to hell and coated in metal shavings, and 2 1/2 bolts fell out when he removed it.

Is that bad? :D
 
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