How to: 4R70W Rebuild Diary Discussion, Questions, ETC

[Mountinheer]

+1 on trans jack...

I thought of replacing the gasket too, but fluid should not be leaking into the space between the cases in the first place... right?

I read somewhere that someone's trans leaked into T-case and they had no idea because the gasket was good. Until the rear seal blew off the t-case...

Biggest problem with removing t-case is you have to rotate it 90 degrees to get it on/off. Think I will build a jig to support it and allow it to rotate.

Thanks for the help!

 

[Mountinheer]

Hmm... 97 F150 has the same seal listed as "output shaft seal" ... so maybe this is right after all?
1997 FORD F-150 5.4L V8 Output Shaft Seal | RockAuto

I would assume this seal is the same for 2wd and 4wd. The shaft is just different length according to original thread.

Would hate to pull Tcase and have wrong seal tho. Maybe I should go to dealer?

 

[CDW6212R]

The 4R70W doesn't have a rear seal, but the extension housing(2WD) has the one referenced. The 4WD/AWD extension has no seal, so you don't need a seal at all.

That rear case gasket is important to keep the tiny amount of ATF from leaking out. The output shaft rides inside the rear case bushing, which generally stops all leakage, all but a tiny amount from wear and old age. That bushing shouldn't get so worn that too much fluid gets past it. Normal rebuilds should include replacing that.

So you at least need that $15 rear gasket, which means yes the TC has to come out again. Sorry to hear how much a PITA that is.

 

[Mountinheer]

The 4R70W doesn't have a rear seal, but the extension housing(2WD) has the one referenced. The 4WD/AWD extension has no seal, so you don't need a seal at all.

That rear case gasket is important to keep the tiny amount of ATF from leaking out. The output shaft rides inside the rear case bushing, which generally stops all leakage, all but a tiny amount from wear and old age. That bushing shouldn't get so worn that too much fluid gets past it. Normal rebuilds should include replacing that.

So you at least need that $15 rear gasket, which means yes the TC has to come out again. Sorry to hear how much a PITA that is.

This is the bad news I was waiting for...

Let me just summarize to make sure we are on the same page. You're saying that there is no rubber seal at the rear of the trans, and I've damaged the internal bushing so severely that it is losing a quart a week. I certainly don't think the case gasket will fix my 1 qt/wk issue... so a complete trans tear-down is the only answer?

Somebody PLEASE chime in and tell me the Bad News Bear is missing something here!

 

[Mountinheer]

This:
4R70W Rebuild Diary - Part 12 - Assembly up to Intermediate clutch

This is what I have to do?

My problem is in the first 3 pictures of that thread? ...

 

[CDW6212R]

I cannot say what that amount of fluid will do, but if it's not pressurized much at all, it won't get past the TC front seal. That 1qt a week is a lot, but it doesn't necessarily meant the trans will go bad soon if you keep going. There isn't an escape for gases inside the AWD/4WD extension. The TC front seal will resist the pressure created by what's in the extension. It's possible that it won't hurt to leave the trans in place as it is. I'd decide that based on how the transmission is operating, if it has issues, or past problems, high mileage etc. Unless someone knows that that fluid will migrate into the TC, I'd go by the trans condition as mentioned.

 

[Mountinheer]

trans is in good shape besides spewing oil.... and you certainly have a point about the seal. I know I read where someone on here had 'Mysterious' trans leak with no drips that eventually blew TC seal.... so I'm hesitant to do the extra work for it to blow up.

guess I'll add a qt and sleep on it.

 

[transman304]

Replace the transfer case to transmission gasket. The area at the rear of transmission is in fluid constantly so it will leak where you tore the gasket. If you are concerned about trans fluid getting into the TC than replace the input seal on case when you have it back out.

 

[Mountinheer]

Yes Sir! Certainly can't argue with transman! (Sorry CDW... you were right, but no trans in your name...)

Thanks for your help guys. I appreciate the confidence boost!

Ordering parts now.

Guess that was a cheap trans flush anyway...

 

[CDW6212R]

ATF is expensive these days. I liked it better when $1 got you a quart of what you needed, and special stuff was $2-3 per. I have some Trick Shift still from the 80's, it was $3.25 from Summit back then. The Amsoil I put in my 4R70W last year was close to $10 a quart, and it took about 16 quarts to fill mine, with a deep sump pan. That's expensive.

 

[Mountinheer]

You're not kidding... I bought 15 qt of Mobile1 ATF... dropped pan to change 5 qt, filled new TC, and I have 1 left. Guess the rest is was expensive rust prevention...