Another Transmission Leak (totally stumped)

Hey everyone,

New member here, so first of all, HI!!

My car has a D&D Performance T56 in it and I've been battling leak issues ever since I bought the car.

The first issue was a defective tail housing casting which had to be sent back for a new one.

The second issue involves the speedo cable and VSS.

When I bought the car, it did not have a speedo cable installed. The VSS was just packed full of RTV to prevent any leaks. I installed a new VSS and a new speedo cable from D&D this past winter and immediately had a fluid leak. It was difficult to tell exactly where the leak was coming from, because there was fluid on the VSS and on the cable where it plugs into the VSS. The fluid would then run down the cable and drip off. I tried replacing the VSS - no dice. I changed the o-ring inside the VSS to a -110 o-ring for a tighter fit - no dice. I wondered if the fluid could be leaking past the crimped metal end of the speedo cable, so I called D&D and they were kind enough to send me a new cable, even though they said they've never heard of this happening. In the meantime, I put my old VSS packed full of RTV back in the trans and drove it without a problem.

I got the new cable and installed it this past weekend - and it leaks again. Same exact place. I'm stumped.

I've searched all over the internet but have never found anyone with this same problem. The leak only shows up when I have a speedo cable installed. When the VSS with RTV in it is installed, there's no leak.

Sorry for the long first post, but I'm totally stumped on this one. Anyone have any ideas?

Could it be the vent tube? The bend in the vent tube sits right above the VSS, so the fluid could be leaking out of the vent cap and running down the vent tube, then dripping on the VSS and cable. I pulled the shifter boot off this morning but didn't see any obvious signs of fresh fluid on the vent tube. I'm going to drive the car home from work today with the shifter boot off to see if I can see anything obvious going on down there while driving.

I wasn't really betting on the vent tube, either. I've read that they can leak oil if something major is wrong and the trans fluid is boiling or the trans is way overfilled, but I don't think either of these is my problem. I changed the fluid shortly after buying the car and made sure to only fill it until it started to leak back out the fill hole (with the car level). If the trans was overheating and boiling the fluid, I think it would leak regardless of which VSS I had installed.

My dad and I are going to get under the car and take a thorough look this weekend. If we can't find anything obvious, I may pack RTV around the speedo cable like you suggested, or just install my other VSS and just live without a working speedo again...

I can check the VSS hole diameter against my dad's T5Z this weekend.

Is it common for T56 castings to have defects? My first tail housing was defective, but I figured this was a fluke. If it is defective, why do you think it would only leak when the speedo cable is installed? Maybe my second VSS is just a bad part?

Yeah, I started investigating those digital converter boxes the first time this leak showed up. They seemed pretty expensive, so I stayed away from them. Hopefully I can find some kind of clue this weekend... I've been battling this stupid leak for the better part of 2 years and I'm about ready to give up and go back to having no speedo. I just can't stand leaks of any sort lol.

Anyway, thanks for your help!

Well, I figured it out.

Got the car home Friday night and sprayed the underside really well with the hose to clean off any old trans fluid. That way, I could see where the fresh fluid was coming from in the morning.

It was definitely the speedo cable leaking. The fluid was running out of the crimped ferrule and dripping off the cable. The ferrule was completely clean and dry, so the fluid definitely wasn't running out of the VSS.

Just out of curiosity, I tried pulling on the ferrule and it came off ridiculously easily. The crimp was for junk. There weren't even any decent indents on the cable made by the crimp. It makes perfect sense that it would leak.

Not trying to knock D&D here; the trans itself has been wonderful and their customer service is always great. It just seems like their cables are pretty poor quality. I don't know where they get them from, but after having two leak like this I would stay away from them.

Stay away from D&D's cables, that is. Not their transmissions!