Im new here and i aint got all this message stuff down but i got a question. Theres a pretty good leak coming from my rear main seal on my 83' 6.2. Iv heard of some stuff called T202 that supposed to stop it, has anybody ever heard of it and if you have how does it work and how well does it work?

I wouldn't ever recommend using any kind of "stop-leak" in an oil system. Make sure you're leaking at the rear main seal first. Some of the common things that leak are the vacuum pump pod on the top of the engine. You could also have a leak on the oil pressure sender or associated connections on the back of the engine on the Driver's side of the engine. You can have a Diesel fuel leak in the engine valley that runs down the valley to the drain hole and looks like oil by the time it get there. Once you've narrowed those things out it's sure possible its a rear main seal leak.

What I do is pull the transmission inspection cover and take a look, if the crankshaft is wet or dripping oil, thats probably your leak. If it's dry there and wet a little bit below, it's probably the oil pan leaking. Thats actually common, I had that happen on one of mine (it's still leaking).

I fully agree with chevydiesel to check everything before jumping to any conclusions. Whoever, I have had two 6.2 with bad rear main seals. In both cases, the seal just came apart and I had a lot of oil loss. It is a real monster to replace because you have to take so much stuff out, including the transmission. Unless you have a very well equipped shop, I wouldn’t even try.

Thanks guys, ill take a closer look today and see whats up

83 6.2's used a rear main rope seal. They were prone to leaking, usually the rope would deteriorate. Replacement isn't very hard, about a 4 hour job. It requires removal of the oil pan, rear main bearing cap and old rope seal. Replace with Fel-pro neoprene rear main seal, don't use pan gaskets, use rtv silicone.:grd:

83 6.2's used a rear main rope seal. They were prone to leaking, usually the rope would deteriorate. Replacement isn't very hard, about a 4 hour job. It requires removal of the oil pan, rear main bearing cap and old rope seal. Replace with Fel-pro neoprene rear main seal, don't use pan gaskets, use rtv silicone.:grd:


I agree. I had an '83 in a former life-time :blahblah: and it had the same (and other) problems. I did just a DC described and , if my memory still works :lol: so did the repair :)

The rear main seal is a rope seal as mentioned earlier. I replaced mine with the Fel-Pro two piece neoprene seal. You do not need to pull the transmission to remove the oil pan, but it is a tight fit. You have to remove the bolt from the left engine mount so you can jack up the engine about 4 inches to get the oil pan out. Be careful to not damage anything top side or the oil lines from the oil filter area to the radiator cooler. Follow the installation directions that come with the seal. Years and years ago it use to be easy to drop an oil pan, but not anymore. And it use to be easy to work on the top side (before polution controls were added).

cougarjohn, I was just curious of this. Can you remove the oil pan without releasing the right motor mount? If so, would you still raise it with a wooden block under the lowest part of the oil pan? My last experience with removing the oil pan was so stressful, I even thought of fabricating a 2 piece oil pan.

I changed the rear seal two years ago. Unfortunately, I messed it up, and it leaks again.

When I took off the pan, I unbolted both motor mounts, and raised the engine from the pan enough to insert 3/8" thick plywood pieces between the mounts and the frame. That gave enough space to take off the pan. It's a bit tight,but can be done.

Now that I think of it, maybe it's the pan that leaks. I put a thick bead of RTV to the rear of the pan, and when I mounted the pan, that RTV bead may have gotten bad at the moment, so it might be the reason for the leak. With some spray-on cleaner and pressurized air, I can make sure where the leak is actually coming from.

If it's the seal, this time I will loosen all the crank bolts to give a little easier fitment for the upper seal half. Last time it was real pain to insert it.

The rear pan seal is a neoprene seal, just like the V-8 gas engine seal. Some techs reuse it, by cleaning with brake-clean and applying RTV sealer. I prefer to replace it. GM sells it separately for the 6.2 as a "rear pan seal".

As mentioned, do not use the after-market paper pan side and front gaskets. Use RTV on the sides and front of the pan. Apply a 1/8" bead all down both sides and the front of the pan in one continuous bead. Overlap the ends where the rear pan (neoprene) seal fits into the main cap.

I use a sticky weatherstrip adheasive to hold the rear pan seal against the main cap after cleaning the surface down to bear metal with brake-clean. I apply a little layer of RTV to the rounded edge of the rear of the pan where it will hit the neoprene just for insurance.

Experience shows the need to apply the sealer and install the pan before the sealer "skins over" (begins to dry). The main problem with RTV is all surfaces must be clean, dry and free of oil residue. Use brake-clean as a cleaning and drying agent.

I raised the engine by putting a 2 X 10 X 10 block and a piece of plywood to prevent the wood block from cracking on the lowest part of the oil pan. You do not want to dent the middle of the oil pan as that is where the oil pickup is located. I first put a small 2 X 4 block between the engine mount and the frame, but I didn't get enough clearance so I think I put in another block of 2 X 4 or 1 X 4 to get more clearance. Extra clearance really helps when you are putting on the RTV and then getting the oil pan up before it hardens!!! I didn't jack the right side of the engine, but you could probably get more clearance by also jacking that side.

Just one more question... I have to replace my flexplate, 3 worn teeth, I think my rear seal is leaking. Is there any problems or need to loosen the motor mounts if the trans is removed. And is it a good idea to replace the rear seal if the trans is out? Thanks all you guys for posting

I don't completely remove the transmission/transfer case to replace the flex plate. I have a trans jack that will handle both units, bolted together. I just roll the two units, on the jack, back to gain a couple of inches clearance. I change the flex plate by holding it with a flywheel turning tool, loosening the bolts with a flex bar and finishing removal with an air ratchet.

Some times, if you get lucky, you can leave one end of both drivelines hooked to the transmission and the transfer case and just slide the whole works back to gain the necessary clearance.

This works on the early trucks, don't know about the late, IFS trucks. I've only done one oil pan on those and had to drop the front differential to get the pan off.

The pan comes off easily on 82-87 4x4's without even messing with the motor mounts.;)

I have an 86 M1028 30K miles clean truck airstrip only I like your setup Cam Greg

Fred Just wondering about the rear seal, I understand sliding the whole unit (T&Tcase) back, what's the next step to replacing the rear seal? Greg

Greg, are we talking one piece rear seal? The seal can be carefully pried out and replaced once the trans is out of the way. There are special tools to bolt to the crank and guide/press the seal in with. I don't have access to them so have just built a "seal driver" tool to use to help keep the seal from being damaged while pulling/tapping it into place.

I used a 3" long piece of thick wall pipe that was the same outer diameter as the seal (or as close as I could find) and welded a flat bar across the top to use to drive against. I drilled two holes in the bar to match up with two corresponding holes in the crank flange. I made two studs, threaded one end to match the crank holes. I threaded the other ends of them to allow nuts and washers to tighten down against the tool and pull the tool and seal into place. I finish by tapping lightly all around the seal to insure it's seated.

The old two piece seal requires removal of the pan, oil pump and rear main cap as described before.

Thanks Fred, It's the two piece seal but when my 6.2 gives up I'll go with a 6.5 n/a which will have a one piece Greg

Is there a thread regarding replacement 6.5 suppliers?

:D You may be awhile!! Those 6.2's are pretty durable!

Yeah, I would like the 190HP instead of the 135 HP, I just can bring myself to do the mods on my J series, but in any case diesel forever. My rig only has 30K on it. I'll never drive another gasser, Viking burial in my truck and Bio is in my future I know....