changing TH 350 oil pump seal while still in truck?

[luna negra]

I'm going to do a 305 to 350 swap on my '79 Jimmy and want to fix the weeping oil pump seal behind the torque convertor while I have the motor out. Buddy of mine said don't do this unless I pull tranny and stand it up on it's tailshaft. First I've heard of this but his reasoning is that internal parts could come loose if the job is done while horizontal. Thoughts on this? Thanks!

 

[Bextreme04]

I'm going to do a 305 to 350 swap on my '79 Jimmy and want to fix the weeping oil pump seal behind the torque convertor while I have the motor out. Buddy of mine said don't do this unless I pull tranny and stand it up on it's tailshaft. First I've heard of this but his reasoning is that internal parts could come loose if the job is done while horizontal. Thoughts on this? Thanks!

You dont need to stand it up, you can absolutely change out the pump seal while it is still in the truck. I will point out that the seal usually starts leaking because the pump bushing is worn. I would suggest you just pull the pump and have a shop do a quick clean and replacement of the bushing and seal. I did that on my TH400 pump while I had it out and a local hotrod shop ran it in his parts washer for a few minutes, blew it out, pressed in a new bushing and seal, and then reassembled the pump for me in about 20 minutes. He charged me $20 for the parts and his time and it hasn't leaked a drop since.

 

[Vbb199]

Just be mindful often times they are usually stuck on there lol

Usually for me, if they're oem, I end up having to take seals off in pieces because it's so seated in

Don't let any fall into the front pump

 

[luna negra]

You dont need to stand it up, you can absolutely change out the pump seal while it is still in the truck. I will point out that the seal usually starts leaking because the pump bushing is worn. I would suggest you just pull the pump and have a shop do a quick clean and replacement of the bushing and seal. I did that on my TH400 pump while I had it out and a local hotrod shop ran it in his parts washer for a few minutes, blew it out, pressed in a new bushing and seal, and then reassembled the pump for me in about 20 minutes. He charged me $20 for the parts and his time and it hasn't leaked a drop since.

I like this idea. I'm concerned why that seal would be leaking anyway. Thanks!

 

[Matt69olds]

There is no reason to completely remove the trans for a CONVERTER seal. Assuming you can slide the trans far enough back to make it easy to access, or the engine is out, it’s pretty easy to change. Carefully knock the old seal out with a chisel, junk screwdriver, whatever. Clean the bore where the seal fits. Look inside the pump, make sure the bushing hadn’t started walking out of its bore. The bushing should be about flush with the pump housing.

If all that checks out, your ready to begin installation.

I like to fill the backside of the desk with Vasoline (DONT USE BEARING GREASE!!) that serves 2 purposes. Purpose #1, it provides plenty on lube on startup. Purpose #2, it ensure you don’t knock the tiny spring out of the seal driving it home. Occasionally, the spring will jump out of its groove, if that happens there is no way to reinstall it with the seal in place. Leaving it loose will definitely result in a leak.

Find a piece of pipe the same diameter as the outer edge of the seal. Square up the seal to the pump, and drive the seal in evenly.

If the O-ring around the pump is leaching, then it’s probably best to remove the trans. Technically, the o ring could he replaced with it in the truck, but you will be fighting gravity. The intermediate clutches/steels will have a tendency to fall out, the forward clutch housing will tend to slide out, just easier to remove it.