While we are discussing Transmission leaks....

[Chief Brody]

I replaced the dipstick tube o-ring on my TH350 last weekend and that didn't stop the leak...it helped, but didn't stop it all....the leak appears to be coming from very near that same spot....is that the modulator or the speedometer linkage right there on the right side of the transmission real close to the dip stick tube?

See those three linear patterns of the leak? One is the fluid dripping off the edge of the pan, one off the front driveshaft and one off the exhaust.

 

[NorCal_Chris]

i posted ths in your other thread.


i had a leaky tube as well... I gobbed the crap out of it with black rtv after getting all the oil off and it is still sealed. Also check around your detent cable, it is just up and forward of the dipstick and may be leaking as well


the detent cable has a plastic housing held in with one bolt on top and has a small o ring. the plastic housing is about an inch long and prone to cracking. Mine cracked and liked to leak. I just made a plug and fixed it and just dealing with not having manual downshifts atm. works ok for me for now.

 

[Chief Brody]

i posted ths in your other thread.


i had a leaky tube as well... I gobbed the crap out of it with black rtv after getting all the oil off and it is still sealed. Also check around your detent cable, it is just up and forward of the dipstick and may be leaking as well

the detent cable has a plastic housing held in with one bolt on top and has a small o ring. the plastic housing is about an inch long and prone to cracking. Mine cracked and liked to leak. I just made a plug and fixed it and just dealing with not having manual downshifts atm. works ok for me for now.

Anybody got a good picture of the right side where this stuff is? I will be looking at it from a tight spot gliding on a creeper...there is so much crap caked up on it I don't know if I will be able to see it.

Also, where did you put the RTV? around the outside or did you coat the tube and jam it in there? I would like to think that a new o-ring would make a nice clean seal....then again, I like to think I have a NP205.....

 

[NorCal_Chris]

Haha I feel you on the space. Yoy can see it better from looking down the dipstick tube AREA under the hood, or take the boot off your trans case shifter and look down and forward its hard to see from below since tge trans flares out and the exhaust is right there. I will try for some pics tom if it isnt raining



On the rtv I jacked the pass side of my truck up so there wasnt fluid right at the dipstick hole and dryed the hole. Cleaned the tube real good and put a new o ring. Then from a little lip above the o ring and down I slathered some rtv on it. It smooshed out the sides a little and has stayed dry since

 

[Chief Brody]

Here is a pic that looks like a clean version of my transmission and one that looks nasty...just like mine:

I am assuming that the black thing is the speedometer cable....I see the dipstick hole....that must be the modulator valve at the rear...what is that circular thing in the middle? Where else do they leak on the right side?

 

[lectric80]

That cable is the detent cable, speedo cable on 4x4's is connected to the transfer case.

Leaks from either the cooler lines, or the detent cable are pretty common. Based on where your leak is coming from I would suspect either the dipstick tube isn't fully inserted or is damaged a bit, or the detent cable o-ring seal is bad.

Edit: The round unit you see is an accumulator (IIRC) and normally you won't see leaks from there.

 

[lectric80]

One final thing, are you certain it is transmission fluid and not 90w oil? The reason I ask is that if it is 90w you could have a leaky front output seal on the transfer case and not an issue with the transmission.

 

[chalet2506]

You might have boogered the o-ring on the tube when you installed it too. I had the same prob with mine after I put a new factory style dipstick in. Tried RTV and it worked for a little bit and then started leaking again. Pulled it and the little o-ring was flattened on one side, must have done that when I put it in.

Replaced with a lokar locking dipstick and it fixed it.

Also, a good way to see into those tight places is to stick your camera in there and get some pics. Then blow them up on your puter.

 

[magik235]

That cable is the detent cable, speedo cable on 4x4's is connected to the transfer case.

Leaks from either the cooler lines, or the detent cable are pretty common. Based on where your leak is coming from I would suspect either the dipstick tube isn't fully inserted or is damaged a bit, or the detent cable o-ring seal is bad.

Edit: The round unit you see is an accumulator (IIRC) and normally you won't see leaks from there.

I just installed my rebuilt TH350 so I am aware of the potential leak sites. Both my dipstick tube and detent cable used a rubber sleeve type seal instead of an o-ring.

 

[lectric80]

My dipstick tube uses a sleeve, but the detent uses an o-ring type seal. Now it is possible they used different styles. I rebuilt my T350 earlier this year so this stuff is still fresh in my mind as well, but by no means can I say they all are setup one way or the other. Most common design I have seen is for the detent to have an o-ring seal.

 

[4X4HIGH]

I've seen dipstick tubes use either an O-ring or a grommett/boot but i've never seen a kickdown cable use anything but an O-ring (not saying it there isn't some that do use a boot).

 

[Chief Brody]

So to remove the detent cable I only need to unscrew that one bolt and then just pull it out...or is there more?

Also, I got these o-rings because I didn't know what size it would take...do you think these will work in the transmission?

The other thing is the speedometer seal I got at the Chevy place:

 

[magik235]

My TH350 rebuild kit came with O- ring and sleeve seals. I just went out to the garage and measured the O-rings. The detent cable O-ring is 1/2" outside diameter X 1/16" thick. The dipstick O-ring is 3/4" outside diameter X 3/32" thick.

 

[Chief Brody]

My TH350 rebuild kit came with O- ring and sleeve seals. I just went out to the garage and measured the O-rings. The detent cable O-ring is 1/2" outside diameter X 1/16" thick. The dipstick O-ring is 3/4" outside diameter X 3/32" thick.

Thanks...the o-rings in my box have 3 measurements...anybody know what's what?

 

[Chief Brody]

oh...I bet it's inner, outer and thickness

So the only one in that box is 3/8 x 1/2 x 1/16

 

[4X4HIGH]

There is ID (inside dimension), OD (outside dimension), and thickness.

 

[Ned Kelly]

Replaced with a lokar locking dipstick and it fixed it.

Chalet,
How hard was that install onto the trans? Yours looks like a nice dirt/waterproof setup. I think I will consider your setup also. Did you do it with trans in the truck? Any tips to pass on? Thanks.

 

[Fordum]

Also, don't forget that dip tube support.
When the dip tube is seated and "at rest", that support should be pretty close to lined up and against the housing.

If you have to push the tube hard or a long way to line up the bolt, then the tube or the support might be bent.

An O ring seals best when it gets equal pressure from all sides. If it is pushed hard to one side, it might not have enough compression on the other side to seal.

 

[lectric80]

No, to remove the detent you will have to drop the pan and remove the spring clip that holds the detent lever, then you can remove the cable end from the lever. There is no way that I am aware of to get the detent cable out without dropping the pan, since you will also need to hook it back up. It is pretty obvious when you get into there.

 

[4xcrazy]

You can remove the detent cable without removing the pan, it's alittle tricky though, as the little lever thingy that the cable connects to just barely reaches the top area of the hole.

It will lose some fluid when you pull that out though, so it may not be a bad idea to go ahead and drop the pan, change the fluid & filter while you're at it, and clean the area real good when installing that o-rind and cable.