700R4 Leaking after new front seal installed.
 

The 700R4 is still leaking from behind the TC after I installed it the 85 in December, I put a new front seal in it then. I am getting ready to pull it out and put it into my 79.

What should I look for when I pull it? I have read that there is a bushing on the front shaft that wears out or the pump housings can crack and leak.

Are these the type of things I can do myself or will I need to bring it to a tranny shop?

Trans works great, it just leaks when it's left sitting for a while.

Re: 700R4 Leaking after new front seal installed.
 

Try a new seal and then make sure the front plate is not leaking at the mounting flange. Make sure the TC does not have a groove in the tube.

Re: 700R4 Leaking after new front seal installed.
 

Does it leak while it's running or when it's turned off. If it's while it's not running it's the O ring around the pump housing. If it's while it's running it could be the torque converter snout has a hair line crack that doesn;t show up until it has fluid pressure...


Chuck

Re: 700R4 Leaking after new front seal installed.
 

I am going to say while it's not running. I haven't run it about a month and I started it yesterday. The truck had been parked facing down a 20 degree or so incline. I noticed smoke after it had been running for about a minute. Traced it down to tranny fluid that had dripped onto the exhaust pipe cross over that is right below the TC. Seemed like it burned off after the truck had run 10 minutes or so. I'll leave it running again today and watch for drips.

If it's the pump O-Ring is that easy to fix?

I have a "New" Tourqe convertor for it. The tranny is from a gas truck. Since it's going in a Diesel I bought a Diesel TC for it. It probably doesn't matter either way but, I just felt better with one from a diesel. I paid more to ship it than I paid for the TC. It's a fairly new looking used unit with Cherry red fluid in it. I got it off one of the guys on the gmc-diesel.com forums.

I looked that one over and there are no grooves or cracks in the TC snout.

Re: 700R4 Leaking after new front seal installed.
 

Parked face down on a 20* incline may be your answer. Get 'er level and look for leaks.

Re: 700R4 Leaking after new front seal installed.
 

Pull the trans out,pull the torque converter out and unbolt the pump housing from trans, O ring goes around the pump housing to seal it to the trans body.

Re: 700R4 Leaking after new front seal installed.
 

Thanks, 72 CustomCamper

I'll replace that when i get the tranny out along with a new seal.

I didn't get a chance to run it again yesterday, I did look underneath it. I parked in the same spot the orther day when I was done with it. There was tranny fluid that had dripped on to the exhaust again, seems like a good amout for just sitting for a day.

Re: 700R4 Leaking after new front seal installed.
 

When you get it all back together, be sure and put some ground wires from the motor to the tranny and from the tranny to the frame. Also from the motor to the frame. Also, be sure and clean the paint off of the back of the motor where it meets the bell housing. My transmission guy told me that grounding was a big cause of transmission failure. When electrical parts in the transmission have voltage applied to them they require a good ground. If they do not have one then electricity will always take the path of least resistance. He has seen many times that the voltage will go through the torque converter and then the pump which will cause arcing on the shaft coming out of the torque converter which in turn will slowly eat away the shaft and cause the seal to start leaking. He was also telling me that it will ruin the pump. It all makes sense to me.

Re: 700R4 Leaking after new front seal installed.
 

Buy a manual transmission transfer case seal for it diesel transfer cases use the manual transmission transfer case seal the np208 in my 85 does and it was a diesel
Hope this helps
Shane

Re: 700R4 Leaking after new front seal installed.
 

You mean use a Diesel TC seal for the front seal on the TH700?

Re: 700R4 Leaking after new front seal installed.
 

Diesel transfer cases have the same size seals as the transfer cases for stick shifts normal auto trans transfer cases had slightly smaller seals.
Shane


Edit CRAP I was thinking of the rear seal not sure about the front one though it my be the same way I'm not sure sorry bout that

Re: 700R4 Leaking after new front seal installed.
 

Replace the brass bushing. I've seen them leak in plenty of transmissions.

Re: 700R4 Leaking after new front seal installed.
 

Thanks gchemist.
You mentioned that bushing in the thread on chevytalk I think way back when I orignally swapped from a TH350C to a 700R4. I gotta pull the pump to do that right?

Is it something a non-trans guy can do?

Re: 700R4 Leaking after new front seal installed.
 

I'm not sure if you need to pull the pump. I'll search around and see if I can find good pictures of the bushing. I'll check my factory manual tomorrow at home.