Rear main seal, input please

i6chick

i6chick

It's all about leverage
Joined
Mar 22, 2009
Messages
409
Hey guys,

Haven’t been on in a while but since I have another project on my hands (89 4x4 automatic), I’m back for some input.

Sister bought back dad’s old truck/my first truck. It changed hands twice, sat in a field for a few years, went back to work hauling a dump trailer and now it’s leaking in my driveway lol.

Fairly certain it’s the rear main. It leaks when its not running a decent amount, and when it runs, especially when cold it leaks a steady stream of oil between the oil pan and the trans.

Questions:

What am I about to get myself into?

Can I slide the trans and the transfer case back enough to get in there without having to actually take everything completely out?

Do I need a seal puller? Or can I just drill or pry it out if I’m careful not to score the crank or housing?

I have heard mixed opinions on lubing the new seal, using soap and water, RTV, Loctite, and putting it in dry. From what I can tell it should be put in dry. Is this accurate?

Is there thread sealer or silicone needed elsewhere for this project?

Should I order a sleeve for the crank as a just in-caser?

Should I also replace that freeze plug down there? I’m a big proponent of not fixing things until they’re broke, and by broke I mean leaking so badly I don’t want to drive it… LOL. Like this truck.

I have heard the flex plates are weak in the first gens. Should I replace the flex plate while I’m in there? What is a good plate to go with? I would like one stronger than stock mostly because I don’t want to have to do any of this a second time, but I don’t need some $400 billet plate. Also, am I opening a whole new can of worms with an aftermarket or later model year flex plate? I’ve read about them tearing up pump seals.

I don’t want to get in way over my head here. I’m comfortable in a little bit over my head but I don’t want to go opening up an automatic transmission even if it is a simple one.

The truck is 27 years old and it hasn’t been a part of our family for 10 years. It’s been a little jerry rigged I think, so I’m just kind of trying to start with unphucking the obvious things first.

Any input of experience would be greatly appreciated. I would love to hear tricks, or tips about this process that might save me time or aggravation. Hell, I’d even take a step by step with pictures if any of you are that bored. If there’s anything else I should look at or replace or go through while I’m in there let me know.

I’m a little intimidated by this project but it has to get done and I don’t see me paying $800 in labor if I think I can pull it off. I mean, how much could I possibly screw up? (that’s not a rhetorical question. Feel free to warn me of all the little things that could go south here.)

Thanks guys.
 
If it's between the trans and oil pan it's most likely the rear main.
However if it's been sitting and such are you positive it's not the rear valve cover gasket?

Are you attempting this job in the driveway or on a lift or??
 
The valve cover gaskets are leaking very lightly but not like this. This is its own, very steady stream unfortunately.

This would be in the driveway or garage if I can manage to squeeze it in. I have a few floor Jacks. I'll probably buy or borrow a transmission jack for this project though.
 
It won't be fun necessarily without a lift for sure but can be done by all means.

I just asked about the valve cover gaskets cause I've seen them do just that and someone would think it was a rear main or huge issue.
 
There are two ways to do this. Number one, get in there, yank the seal out with a screwdriver, puller, etc, then slam the new one in. Number two, remove the adapter plate and starter (as one piece) and remove the entire rear main seal housing, then replace the actual seal out of the truck, and re install the whole unit. To answer your questions:

i6chick said:
Can I slide the trans and the transfer case back enough to get in there without having to actually take everything completely out?

Its not worth the aggravation, You will be better off removing it completely so you can get in there and do the job correctly.

Do I need a seal puller? Or can I just drill or pry it out if I’m careful not to score the crank or housing?

You can usually pry it out, I've heard of people drilling a small hole in them and using a small dent puller/slide hammer. If you remove the entire housing you can do it on the bench with a punch and hammer.

I have heard mixed opinions on lubing the new seal, using soap and water, RTV, Loctite, and putting it in dry. From what I can tell it should be put in dry. Is this accurate?

Stick her in dry :lolly: In all seriousness, no lube, no sealer, no nothing, just put it in there

Is there thread sealer or silicone needed elsewhere for this project?

Maybe for the method of removing the adapter plate and taking the housing off, then you'd want to silicone goup up where the rear main seal housing meets the oil pan gasket and all the way across the back of the oil pan

Should I order a sleeve for the crank as a just in-caser?

Never seen one that's actually needed a sleeve. It's rare.

Should I also replace that freeze plug down there? I’m a big proponent of not fixing things until they’re broke, and by broke I mean leaking so badly I don’t want to drive it… LOL. Like this truck.

Don't mess with it if it's dry

I have heard the flex plates are weak in the first gens. Should I replace the flex plate while I’m in there? What is a good plate to go with? I would like one stronger than stock mostly because I don’t want to have to do any of this a second time, but I don’t need some $400 billet plate. Also, am I opening a whole new can of worms with an aftermarket or later model year flex plate? I’ve read about them tearing up pump seals.

Valair sells a nice flexplate for like 100 bucks. I have used these and they work well. Link

I don’t want to get in way over my head here. I’m comfortable in a little bit over my head but I don’t want to go opening up an automatic transmission even if it is a simple one.

You should be fine, It would be a good time to dump the converter out and drain the trains to get a bunch of fresh oil in there though
Click to expand...

As stated before, just be sure its not the rear valve cover gasket. I've definatly seen those give the illusion of a rear main seal or oil pan leak before.

Typically, I try to remove the whole housing and replace them on the bench. They usually work out really well that way since you can clean them up nice and then hammer it in there straight on the bench, as opposed to doing it under the truck.

Good luck!!! :Cheer:
 
I've been part of drilling them and using a small slide hammer before and it worked well. Kinda 14 different ways to skin a cat as he said.
 
I use the slide hammer w a sheet metal screw in the end. TAP and twist it in, then pull it out.
THERE is a retired dodge engineer on ebay selling a traditional spring style seal. He claims the fancy ones cannot take up the tolerance stackup.
 
I tap the seal with a punch to loosen it up. Then run 2 small self tapping screws 180* apart. Then use a fork tool to pry it out. Brake clean & scotch pad to clean surfaces. I bought the tool from quad4x4 that installs them square.


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samiam44 said:
I use the slide hammer w a sheet metal screw in the end. TAP and twist it in, then pull it out.
THERE is a retired dodge engineer on ebay selling a traditional spring style seal. He claims the fancy ones cannot take up the tolerance stackup.
Click to expand...

This, why? Have you done a first Gen with a regular old seal? If this chit leaks again I will probably shoot myself.

Finally back in town to start this project this evening. This is gonna blow, I can already tell.

Thanks guys for all the input.
 
BRE said:
I've been part of drilling them and using a small slide hammer before and it worked well.
Click to expand...

x2
Guy at my last job would put a construction screw through it and yank like hell with vice grips. Seemed to work.

Don't try and pry it out with a flat head. The surrounding material seems to break pretty easy.
 
Careful drilling. Won't take much to get off track an phuck up the seal holder. I just removed oil pan an seal holder an installed off truck.
 
Hold up, I think I messed up.

I was just under there looking at everything I was going to have to remove to get the trans and transfer case out and it just didn't smell right to me. Last week before I left for SEMA I did a trans service on it. The fluid didn't smell like much to me, was pretty black and in terrible shape. I moved the truck around to where I wanted it to stay for this project in the driveway and of course when you crank it up (and put it into reverse, I should have thought about that before) it pours out of what was looking like between the oil pan and the trans. Now it looks like it's just leaking out of the little plate on the underside of the tranny. Smells a bit more like trans fluid than engine oil and has a reddish tinge. I'm assuming I couldn't tell much difference before cause the fluid was in such piss poor shape.

Could I have misdiagnosed a huge converter seal or pump seal leak for a rear main? I'm glad I took a second to look everything over again in the day time. I might have something else going on.
 
bigstacks95 gave out some sound advice.

I would go a bit further & replace the converter with one a few hundred below stock stall, replace the flexplate with a second gen Cummins unit, and if you're going to beat on the truck, may as well do a billet rear freeze plug...if you live somewhere cold, get the one that allows you to screw an elbow into it & run a foot of 5/8" heater hose directly to the heater core input's water valve.
 
"This, why? Have you done a first Gen with a regular old seal? If this chit leaks again I will probably shoot myself. "

Yes I did mine when I put the 47RH in my truck.


M
 
ofelas, you say run a short 1ft piece of heater hose directly to the rear freeze plug fitting.. is this just for faster heat or better circulation..?
 
i6chick said:
Hold up, I think I messed up.

I was just under there looking at everything I was going to have to remove to get the trans and transfer case out and it just didn't smell right to me. Last week before I left for SEMA I did a trans service on it. The fluid didn't smell like much to me, was pretty black and in terrible shape. I moved the truck around to where I wanted it to stay for this project in the driveway and of course when you crank it up (and put it into reverse, I should have thought about that before) it pours out of what was looking like between the oil pan and the trans. Now it looks like it's just leaking out of the little plate on the underside of the tranny. Smells a bit more like trans fluid than engine oil and has a reddish tinge. I'm assuming I couldn't tell much difference before cause the fluid was in such piss poor shape.

Could I have misdiagnosed a huge converter seal or pump seal leak for a rear main? I'm glad I took a second to look everything over again in the day time. I might have something else going on.
Click to expand...



Since no one has answered you yet. Yes it is possible and very easy to do. Question is are you comfortable pulling the pump to install a new pump seal or is that too far in for you?


Sent from my iPhone using Tapatalk
 
Hi. The rear freeze plug area is home to stagnant coolant, that runs a bit hotter than the rest of the cylinder head. Hope that answers your questions. :Cheer:

BIGTRKMAN said:
ofelas, you say run a short 1ft piece of heater hose directly to the rear freeze plug fitting.. is this just for faster heat or better circulation..?
Click to expand...
 
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