4R70W Front Seal Leak After Rebuild.....
11-05-2018, 05:29 AM
#11
Senior Member
Originally Posted by retiredinoregon
Just checking back in with this project....I've had the transmission out, and back in numerous times now. Checked everything. New sealing rings on the pump, new bushing, new torque converter, new front seal, new flex plate AND a completely rebuilt unit. When I start it up, it gushes fluid from the inspection hole in the bell housing. I have not a clue. I'm at the point now where I've got $800 in the rebuild, and I can't drive it so I'm going to have to strap some kind of container to the bottom of the bell housing to catch the fluid (@ $5/qt), and just move it out of the driveway and out of everyone's way. It saddens me greatly, but it seems no matter who I call, no one... and I mean no one.... can seem to tell me WHAT will make a transmission gush fluid right past a new front seal...in Park, Reverse, Drive, Neutral...doesn't matter. As an Engineer myself, I'm truly shocked that I get the same answers over and over again: Front seal, pump gasket, front bushing. That's it. There is SOMETHING that can cause a tranny to put pressure against that seal that it was never intended to hold, and whatever that 'thing' is, it's happening here. When I find out...IF I find out.... I will post the result in detail. In 35 years of wrenching on cars and trucks, I've never seen a front leak this bad that didn't reveal a bad seal upon removal. Ever. I'm no professional mechanic, but I know for certain this seal isn't supposed to have this kind of pressure against it. Stay tuned, lol.
The following 2 users liked this post by Fordrocks689:
Blondie70 (10-05-2023),
retiredinoregon (11-07-2018)
11-14-2018, 10:23 AM
#12
Brand new rebuilt transmission gushes 3 1/2 quarts of fluid in 2 minutes, right past a brand new front seal....and no one in the world of transmission repair seems to be able to tell me why, or even what could cause pressure like that against this seal.
This has been going on for 5 months. I've never even had the chance to see if the damned thing will move, because it won't stop gushing $5/qt fluid out of the front seal long enough to even pull it down off the ramps.
Anyone want to buy a '97 F150 4x4 with a new tranny?
This has been going on for 5 months. I've never even had the chance to see if the damned thing will move, because it won't stop gushing $5/qt fluid out of the front seal long enough to even pull it down off the ramps.
Anyone want to buy a '97 F150 4x4 with a new tranny?
11-14-2018, 10:36 AM
#13
Senior Member
Did you replace the torque converter? Are you sure it's not coming out of the converter?
11-15-2018, 12:20 PM
#14
Senior Member
Torque converter or maybe a cracked pump, in my case it was the converter. You would think it would just about have to be one or the other, but never say never I guess.
02-09-2023, 06:25 AM
#15
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Not sure if this has happened to anyone else, but I rebuilt my 4R70W transmission from my '97 F150 4x4, 4,6L, bone stock. I replaced most all of the hard parts with either new or rebuilt, and rebuilt the valve body and added a shift kit as well, and the torque converter is a rebuilt unit, so everything is stock all around.
I've installed, pulled and re-installed this thing 3 times now...and every time, the front seal leaks. And not just a "drip"...it leaks. I put about 10 quarts in to start it up, it doesn't leak, sounds fine etc....not a drop. But as soon as I start cycling it through the gears to circulate fluid, it starts leaking....about 1 quart in 2 minutes. The pump is rebuilt, the front seal is new, the pump gasket is new and there are no cracks in the case. I am perplexed. My scientific wild *** guess says that pressure is being placed on the seal that doesn't belong there...but that's obvious. I'm not a transmission expert, but every time I call one I get the same answers.....front seal, spring in the front seal, bad gasket, cracked case.... etc, etc... So, if this happened to anyone else, please share...if not, let's figure this thing out and let everyone know about it.
I've installed, pulled and re-installed this thing 3 times now...and every time, the front seal leaks. And not just a "drip"...it leaks. I put about 10 quarts in to start it up, it doesn't leak, sounds fine etc....not a drop. But as soon as I start cycling it through the gears to circulate fluid, it starts leaking....about 1 quart in 2 minutes. The pump is rebuilt, the front seal is new, the pump gasket is new and there are no cracks in the case. I am perplexed. My scientific wild *** guess says that pressure is being placed on the seal that doesn't belong there...but that's obvious. I'm not a transmission expert, but every time I call one I get the same answers.....front seal, spring in the front seal, bad gasket, cracked case.... etc, etc... So, if this happened to anyone else, please share...if not, let's figure this thing out and let everyone know about it.
Same problem suspect transmission flow issue when hot or clog in system or check valve leading to excessive pressure
09-14-2023, 01:04 AM
#16
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09-14-2023, 08:56 AM
#17
After all the trouble and multiple seal failures, you need to explore all options
I agree to check the converter for a pinhole in the weld
Yes, always use the red trans assembly grease on the seal to hold the garter spring in place
If the garter spring was the issue you'd have to fish it out separate from the old seal and you would notice that IMO
As far as excess pressure on that seal, there are line pressure tests you might want to perform
Maybe Mark K will chime in about that
I agree to check the converter for a pinhole in the weld
Yes, always use the red trans assembly grease on the seal to hold the garter spring in place
If the garter spring was the issue you'd have to fish it out separate from the old seal and you would notice that IMO
As far as excess pressure on that seal, there are line pressure tests you might want to perform
Maybe Mark K will chime in about that
10-05-2023, 07:53 AM
#18
Not that I know of. But I have the same issue. Although not as severe. I just put the truck on the ground last night from putting a new front seal and pump gasket. Everything seemed fine, until the test drive. I might have driven half a mile, so a mile total. Checked as soon as I pulled in the driveway and there it was. Leaking out of the inspection port. I'm so confused 
10-05-2023, 09:13 AM
#19
You took a digital caliper to the converter hub to check its diameter right?
You installed the new seal on the bub to check its fit?
You used the special tool to install the hub seal?
You might want to watch a few videos by Richard at Precision Transmission
He has a good one on the 4R100 titled
"What we are making, and how do we get a 4R100 to handle"
At about 19 minutes into the video (on YouTube) he goes into the front seal and pump (the grey seal and the additives)
At about 24 minutes in he talks about crank wear and bushing in the front pump wear at the bottom only
Good luck
You installed the new seal on the bub to check its fit?
You used the special tool to install the hub seal?
You might want to watch a few videos by Richard at Precision Transmission
He has a good one on the 4R100 titled
"What we are making, and how do we get a 4R100 to handle"
At about 19 minutes into the video (on YouTube) he goes into the front seal and pump (the grey seal and the additives)
At about 24 minutes in he talks about crank wear and bushing in the front pump wear at the bottom only
Good luck
The following users liked this post:
Blondie70 (10-05-2023)
10-07-2023, 05:36 PM
#20
4R100? I'm working on a 4R70W. It's in a 1997 F150 4X4 w/ a 4.6L VIN6. I knew about the gray seal and additives. I did watch an entire course on the disassembly and reassembly of a 4R70W at TransmissionBench.com. Also on YT under Transmission Bench. They guy is a bit dry and I personally don't agree with some of his methods. For example, using a large flat head and a hammer to remove the pump bushing. Just seems to risky when working with aluminum. But then again, that might be common practice. I don't know, I'm most definitely NOT a transmission guy!!!
I've yet to see anyone use a special tool working on these pumps. So I'm a bit confused there. Yes, I did put calipers on the torque converter to make sure it is still round and not oval. The finish on the torque converter shaft is perfect. No pitting or grooves in it. Ran a fingernail over it and was fine. Nothing to stop my nail on. Slicker than snot on a doorknob.
I have watched several videos from Precision Transmission. So I think I have a firm grasp on what to look for. Additionally, I'm not ruling out mistakes on my part. As far as the new front seal is concerned. Anything can, and usually does around here
, happen. Thank You Sir for responding!! ANY advice or words of wisdom is GREATLY appreciated!! Because I'm loosing my mind over here stressing out over this!!
I've yet to see anyone use a special tool working on these pumps. So I'm a bit confused there. Yes, I did put calipers on the torque converter to make sure it is still round and not oval. The finish on the torque converter shaft is perfect. No pitting or grooves in it. Ran a fingernail over it and was fine. Nothing to stop my nail on. Slicker than snot on a doorknob.
I have watched several videos from Precision Transmission. So I think I have a firm grasp on what to look for. Additionally, I'm not ruling out mistakes on my part. As far as the new front seal is concerned. Anything can, and usually does around here
, happen. Thank You Sir for responding!! ANY advice or words of wisdom is GREATLY appreciated!! Because I'm loosing my mind over here stressing out over this!!
