700r4 leakage

[Subzilla]

I've got another leaker on my K5. I'm having to add a pint of trans fluid about every 500 miles or so. Crawling under it last night, it appears to be coming from between the NP208 case and the aluminum support piece between the trans and transfer case. I really need to clean it, then reinspect it. My question, I'm assuming there is a seal at the back of the transmission but should there be fluid in this support piece between the transmission and transfer case? How does the transmission shaft connect to the transfer case? It's been about 5 years since I've dropped all of this stuff on the Sub so I can't remember how it all goes together. I don't think the transfer case halves or thirds are leaking at the seams.

I guess I'm just trying to do my homework before I get deep into disassembling it.

Thanks

[DmaxMaverick]

It is likely the tranny output shaft seal. Easily replaced with the TC and adapter (tail shaft housing) removed.

You can also get a leak at the adapter if the TC is overfilled (they use the same fluid). The adapter has a weep hole, and fluid can come from forward-back, or back-forward. The adapter should be dry, if all seals and fluid levels are good. The tranny/TC are splined together.

[Subzilla]

I thought it would be something as simple as a seal. I keep a check on the transfer case fluid level and it is not overfilled. How can it be? You can only fill up to the fill hole and no more. IIRC, the fluid should be up to the hole. Correct?

Thanks for your help. Gotta get the wrenches out now.

[diesel65]

There is no output shaft seal on a 4x4 transmission case, There is a input shaft seal on the transfer case.
There is a gasket between the adapter and the transfer case, between the transmission and the adapter there is a o-ring that is square in cross section.

[Subzilla]

So William, are you saying the trans fluid does flow into the adapter from the transmission? And my leak is likely either the gasket or o-ring you refer to? I haven't dropped the TC, yet.

Thanks!

[diesel65]

Yes, It is wet in that area.
Could be loose bolts.
When the transfer case is down I inspect the input seal to see if it is hardened from the heat, I use a pick and see if it is still pliable.
This is where to look if you are loosing trans fluid and overfilling the transfer case, because of the hardened seal.

[Subzilla]

Went to Transtar (formerly Axiom) transmission parts warehouse. The lady looked it up for and said I would need the double lip, transmission output shaft seal; the NP208 input shaft seal; and a 6-hole adapter gasket. That should fix any leaks.

Still a little confused here but we'll see what we have. I drop the TC in the next couple of weeks and check it out. Thanks for the responses!

[Subzilla]

Report: Finally got to playing under the Blazer this week. After disconnecting everything and strapping the transmission floor jack to the transfer case, I go to remove the final 4 bolts holding the adapter to the transmission. Whoaa! One bolt is missing and another is loose. The other 2 are somewhat tight but not enough to keep the fluid from leaking out at the big O-ring! There's your problem, Vern. Even worse, the previous mechanic (before my ownership) used SAE for 2 of the bolts and a metric for the other one. The SAE bolts had aluminum thread rings on them from the cross threading into the transmission - not good. I ran the metric bolt down the holes and it seems fine. So I'm off to the store to get 3 more metric bolts.

I'll break open the transfer case to reseal, replace all the other seals including the O-ring, then hook it all back up. Not too tough of a job but I sure wish I had a lift in my garage! Up and down many times on the creeper makes for a sore back and neck the next day!

I did notice the previous mechanic had mixed up a few other bolts for the TC support. Gotta love quality work! Had I seen the loose bolt situation, I probably could have save myself alot of time by just repairing this and not dropping everything! Oh well, preventative maintenance is always good.

[Robyn]

I would certainly separate the boxes and replace the o rings between the adapter and the tranny and the T case too.

It may be a good idea to install Helicoils in the threads that were damaged.

The 700 if memory serves is metric all the way.

There is a seal in the front of the T case at the input collar to keep tranny oil and T case oil from swapping.
There is nothing in the rear of the tranny at all and the oil can flow through the adapter and then it runs back to the pan via a drain hole.

The governor is in the back of the tranny and runs off a spiral gear tooth on the output shaft so it needs lube.

The adapter should be cast steel but I have seen some aluminum ones too.

Be sure the O ring contact area is clean and free of any crud.
Just a little bit of grease is all you need on the O rings to make them seal well.

Be sure the replacement bolts are grade 5 or better and penetrate the threaded holes properly to give good holding power.

I know you really did not wish to tear into this very far, but, now is a great time to fix it right so it will be all well for the winter season that is soon to be apon us :eek:

Best of luck

Robyn

[DmaxMaverick]

I'll echo Robyn's recommendation. Have all of those holes Heli-Coiled (important in aluminum bores for even clamping). It isn't too expensive at a machine shop, and you have it out now. You really don't want a torque bias on that coupling. If you don't, you may be somewhere much less convenient when they let go, and the odds (and Murphy) say they will.

[Subzilla]

I agree about repairing the holes! The problem is the threaded part is on the transmission which is still attached to the vehicle. The bolts go in from the adapter side into the transmission housing.

Always something!

Thanks for the advice.

[DmaxMaverick]

You could DIY the repair, on the vehicle. A complete Heli-Coil kit (includes bit, tap, insertion tool, and inserts) will cost less than $50. It's easy to do and completely effective if you are careful (as in, follow the instructions). I get my Heli-Coil kits HERE (http://www.nationaltoolwarehouse.com/xq/asp/TID.%7B7BF29EDB-7053-4D42-9829-20D9D0DC27E8%7D/st.2/search_phrase.Heli-Coil/qx/results.htm). Realistic prices, and a complete listing of all products available.

[Subzilla]

Thanks for the link Dmax. I keep this handy for the future. I plan to DIY but I want to finish up the job this weekend. I know that most auto parts stores have the Helicoil kits so I'll do some running around tonight. Never done this before but I ain't afraid to try! Looks pretty easy but I know it will be important to keep everything squared up while drilling and tapping. With the transfer case removed, I can pretty much sit under the Blazer and look squarely at the end of the transmission so I should be able to accomplish the task fairly easy.

I'll let ya'll know how it goes.

[DmaxMaverick]

I try to shop local when I can. I use their site not only for ordering, but for part identification. They list the brand specific part numbers. You can use the site to ID the kit you need, then shop around for it. It's a lot easier to go to a supplier with the correct part number, and you take a lesser chance of getting the wrong part. You might also contact a machine or tranny shop. They may be able to set you up with what you need.

[jasondmann]

I don't want to hi-jack the thread but does anybody know if there is an output shaft seal on the 4l80e? It sounds like I am having the same problems.

I work as a mechanic on heavy equipment and it is embarrassing when people do shady jobs like that, I believe in taking pride in your work. My foreman doesn't like when I refuse to do a job that I don't get the right parts for and am expected to just make it work. I hope that the heli-coils work, they are not too had to do, just be sure to be square to the hole.

[Robyn]

The seal is in the front of the T case and keeps the oil from leaking into the case.

There are two O rings or gaskets in the adapter, one at the tranny and one at the T case.
Depending on the application the "seal" can be an O ring or a gasket between the adapter and the tranny or T case.

Many times the tranny shops get sloppy and dont replace the o ring or gasket when they break the boxes apart or worse yet they are not careful to make sure the mating surfaces are clean when reconnecting them.

Also as was mentioned above, the bolts get mixed with the wrong kind and threads get loused up.

Good luck

Robyn

[Subzilla]

Update: Spent half my weekend chasing down thread repair kits and the associated drill bit. NAPA had the premier Heli-coil plastic bag kit for $50, Carquest had a cheaper, cardboard-backed Heli-coil version for $35, Advance Auto had an even cheaper Heli-coil brand version for $20 but didn't have the right size for me. They all serve the same purpose - why the difference in price and kits? I opted to get the Autozone "Fix-a-Thread" version also for $20. I'm hoping the "off" brand will be fine. Now the search for a 25/64 inch drill bit also took some time. Autozone didn't have the size for their own kit, Northern Tool was out, Lowe's saved the day! Ended up not having much time to mess with it over the weekend. Too many other distractions.

Monday: Drilled, tapped, and coil inserted the 4 holes with ease and speed. Hammered on an ever-so-slightly oversized TC output shaft seal for 45 minutes to install it. It's a miracle I didn't damage this one (like the first one!).

Wednesday: Sealed up the TC halves and put the large, rubber o-ring on the adapter after thoroughly cleaning it. Slid that 100 pound pig back under the Blazer and rolled it up onto the jack. Not enough clearance to put on the jack then roll it under. Now ready to roll it into place and connect everything back up. 8:30 pm, hungry for supper, halted work and ate.

Tonight: Will hook it all back up tonight.

Not too bad of a job - normally.

[Subzilla]

Buttoned it all up on Friday! Filled her up, drove down the road, rechecked fluids, parked in garage overnight with absolutely no bright pink stuff on the floor the next morning! Life is good, again.

[Robyn]

Gotta love it when a plan comes together for sure. :D:D

Glad all is well

Robyn