Need some advice on rear leak

bigrob · #1 (**permalink**) 05-08-2008, 05:51 PM

I have a leak from the back of my tranny. I was assuming it was getting past the seal, but when under the car today, the output shaft seemed nice and dry & the seal looked OK. The fluid was dripping from the U joint at the front of the Drive shaft. The fluid is tranny oil, did a fluid change yesterday and it is nice and clean! I did a search and saw some talk about the DS yolk when talking about rear leaks and was hoping someone could go into more detail for me! I appeciate any help as always!!

nevermind65 · #2 (**permalink**) 05-09-2008, 05:39 AM

I've seen them leaking from where the speedo gear goes into the trans. There is usually just a rubber o-ring and after a while, they can dry up and crack.

Just a thought.

Clois Harlan · #3 (**permalink**) 05-09-2008, 06:21 AM

If I were a smart A _ I would say eat more cheese but since this is a problem I had sometime ago I would bet your problem is the rear seal in your transmission tail section. Mat Twiehaus had a similar leak and had his fixed last week. The biggest deal for him was pulling his tranny from his Lone Star (Must pull engine). The cost at the transmission shop to replace front and rear seals was only $35 but it was a weekend job.

Get some brake cleaner and spray clean everything off and wipe dry. Then take your car out for a short drive and bring it home and jack it up and take a better look at the various suspect areas. Hopefully, it will be your speedo gear.

Clois

CJ428CJ · #4 (**permalink**) 05-09-2008, 08:37 AM

Get some of that dye that you add to the oil. It's amazing how an oil leak in one place can barely creep a long a seam or something and look like it's coming from somewhere else. I bought a kit with the dye, a special light and some special glasses. One of the best investments I've made. Now I can see where the leaks are coming from rather than having to guess.

Chris

Jimi G · #5 (**permalink**) 05-09-2008, 08:50 AM

bigrob, I have seen driveshaft yokes crack and cause oil to leak out of the yoke itself, although it is rare. The first thing I would do is drop the driveshaft and inspect the rear of the yoke for a crack and also check out the surface on the yoke that the seal rides against. If the yoke has a groove in it this will also cause a leak and while you are there I would look at the rear seal a little closer as well as the speedo connections. jimig@standardtransmission.com

patrickt · #6 (**permalink**) 05-09-2008, 08:54 AM

Quote:

Originally Posted by CJ428CJ

Get some of that dye that you add to the oil. It's amazing how an oil leak in one place can barely creep a long a seam or something and look like it's coming from somewhere else.

100% Correct. I had a leak that appeared to be coming from the transmission (and a leak that was dripping from the frame) that I simply could not find the source. As soon as I used the dye to the engine oil I was able to trace it to my IM/Head/VC area and take care of it. Before you assume it is transmission oil, use the simple dye test first to make sure.

bigrob · #7 (**permalink**) 05-09-2008, 09:43 AM

Thanks for the help guys. The dye sound like a really good idea & I think I may go that route.

patrickt · #8 (**permalink**) 05-09-2008, 09:49 AM

Quote:

Originally Posted by bigrob

Thanks for the help guys. The dye sound like a really good idea & I think I may go that route.

AutoZone has a deal where you get a UV flashlight, two bottles of dye, and some magic goggles all for about $20. I'll tell you, I was a little surprised when I put the flashlight on the puddle of oil under my transmission and it glowed in the dark after having put the dye in my engine oil. I was then able to trace the leak to its source. The leak trail was so small and hard to detect that you really couldn't see it without the dye.

RICK LAKE · #9 (**permalink**) 05-12-2008, 05:42 AM

bigrob Some yokes have a small pinhole in the yoke to let the air bleed out from slid joint. This is between the yoke splines and the trans output shaft splines. On some setups you have to put a little RTV about an inch into the yoke all the way round. Wheel bearing grease works well too but breaks down over time. This stops the trans fluid from leaking by the splines and out the hole if the yoke has one or remove the yoke and weld the hole closed. If it's the speedo outputcase, clean the area and install RTV around where the seal is. Make sure area is clean and let sit for 24 hours. Grey color RTV ONLY. The other thing is if the old trans fluid was well used, it looses it's wieght, 70W-90 and it gets thinner, some times it starts to leak out through seals. The problem I have seen is adding new fluids where old worn out fluids where and getting leaks. Output shaft seals are a common failure problem on high milage or hard drivin cars. Good luck with the leak, the dye works the best for finding them. Rick L.