# Transmission Fluid Leak at Speedo Cable Housing



## shimelhoch (Dec 9, 2009)

I have 69 LeMans 350 with a TH-350 Transmission. I have a tranny fluid leak from where the speedo cable connects to the speedo gear housing. I replaced the gaskets but I am still having a leak. I have also checked the tranny fluid level cold and hot, to make sure I have the correct amount. Here is what I have observed:

*I do not see any leaking tranny fluid from the speedo cable connection immediately after driving the vehicle

*The next morning, there is a small puddle of fluid under the car and it comes from where the speedo cable connects to the speedo gear housing.

I have ordered a new driven gear (36 tooth) and driven gear housing which I plan to install next week to see if that solves the problem. If it does not, I plan to next replace the speedo cable. I am baffled as to why I don't see the leak immediately after driving. Any one with a similar experience? Any thoughts?


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## Flambeau (Dec 30, 2013)

I have the same problem, bought the new "o" rings but haven't installed them yet. Im interested to hear what others say.


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## GTO JUDGE (May 14, 2005)

WOW I have been suffering with this since last summer in my TH400. Speed driven gear is fine no cuts it looks perfect, was installed in 2011. Same drip from cable. Installed 3 new cups making sure the metal clip sits atop the cup. Also making sure the grooved end faces inward so tranny fluid would spread the cup when force from acceleration happens. Also put 2 new O rings in. 

Thought the problem was fixed then 7 days later.......drip. So, Both Ames and PY now carry a new housing and they now carry an apple shaped shaft seal with a spring around the end. See Pic

This is a new style it appears. This fits TH350 and TH400, for 3.00. 
There is only a couple things that can cause this, the housing or the speedo gear. I ordered a new housing (R158NT) TH350: R158NVA both sell for 35.00.

I also ordered 2 extra shaft seals. The housing comes with the o ring and shaft seal installed with a metal retaining clip. I don't know if it has the new shaft seal installed as I left well enough alone. I installed it. 2 weeks later no drip. However..... the following day I put my hand on it and got fluid but no leaks. Could be from tranny fluid backing up into the cable and upon reinstalling it, it leaked back out. I check this daily and so far no leak..... If it happens again the next step is to install a new seal and a new speed driven gear although this gear looks fine. I had no problems until all the sudden last year.

The new housing is identical to the OEM one except its missing the OEM stampings.


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## shimelhoch (Dec 9, 2009)

Great insight GTO Judge. I'll be sure to post once I install the new parts I ordered. I am hoping that the new housing which come with a shaft seal plus the new gear will do the trick if not, next step may be the shaft seal you mentioned. Thanks again for your response to this post!


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## shimelhoch (Dec 9, 2009)

UPDATE: I installed the new driver gear and driven gear housing. Still leaking but significantly less. I am thinking that the speedo cable is not sitting flush on the housing where it screws on. I will be ordering a new speedo cable and we will see if that does the trick. One small step at a time.....


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## GTO JUDGE (May 14, 2005)

shimelhoch said:


> UPDATE: I installed the new driver gear and driven gear housing. Still leaking but significantly less. I am thinking that the speedo cable is not sitting flush on the housing where it screws on. I will be ordering a new speedo cable and we will see if that does the trick. One small step at a time.....


Did you drain the fluid from the cable? If its leaking, fluid will be forced into the cable itself when on the throttle and will back drip out until its all gone. Wipe the area down and watch it for a few days to see if it stops. When I installed the same, the next drive the area was wet to the touch. the reminiscence of fluid that was forced into the cable was back dripping out. I wiped it down and so far so good its not leaking. Maybe yours is back dripping?


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## shimelhoch (Dec 9, 2009)

I will check for that, good thought. One question....When I tightened the speedo cable to the housing I only went finger tight. I screwed it in and tightened it as much as I could without using the aid of a tool. It seems pretty snug. Is it recommended to screw on only finger tight or should I use a vice grip pliers to get another 1/2 turn out of it?


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## GTO JUDGE (May 14, 2005)

shimelhoch said:


> I will check for that, good thought. One question....When I tightened the speedo cable to the housing I only went finger tight. I screwed it in and tightened it as much as I could without using the aid of a tool. It seems pretty snug. Is it recommended to screw on only finger tight or should I use a vice grip pliers to get another 1/2 turn out of it?


It should be finger tight +. I used open end lock jaw pliers just to give it a tad more than finger tight. You don't want to round over the splines or go too tight and crack the threaded area, just a little more than finger tight don't go near 1/2 a turn. Hopefully that's all you need. I noticed the speedo gear fit tighter with the new inner seal in the housing and the cable screwed on tighter too Better fit all around.


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## shimelhoch (Dec 9, 2009)

UPDATE: PROBLEM SOLVED

So I was still getting leaking from the speedo cable/driven gear housing connection point. This is after installing new seals, new driven gear and new driven gear housing. So, there was only one part left to replace, the speedo cable itself which I was somewhat avoiding since its sort of a pain to disconnect from the speedometer. In any case, I tackled it last weekend and no more leak. Apparently, the lip on the old speedo cable must not have been sitting flush on the speedo gear housing and was allowing tranny fluid to leak.


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## eeyore (Oct 23, 2014)

There is a small o-ring inside the gear housing (bullet) that seals against the driven gear shaft.

Also check the trans vent tube on the right side near the top of the case. Could be clogged.


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