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Old 05-01-2003, 08:12 PM
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Post tranny leak

OK i just got my tranny rebuilt not to long ago and then soon after got my driveshaft shorten 3/4 on an inch. when i put the drive shaft back in it started to leak out the slip yolk. well i pulled the shaft back out and looked and there was a hole on the middle of the yolk so i replaced it with a yolk that seemed to have that little hole spot welded. well it i thought the probluem was solved untill one day maby a month after i did this is randomly starts back up leaking again. i havent had time to pull the shaft back out and look but it is leaking from the same spot.

any ideas whats up with this???????

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Old 05-01-2003, 09:32 PM
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That hole is there for a reason. When the yoke slips back and forth with suspension travel, the hole allows the space beteen the yoke and tail shaft to vent. Without it, hydraulic pressures will build up and may damage the tranny due to forces being transferred when the suspension bounces. The spot weld got blown out due to the high pressures. You want the hole open.

Fluid is leaking out there because either your tranny is overfilled and the level is above that point or you tranny slopes backward severely which stacks the fluid down there. Normally fluid should never be that high in the tranny.
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Old 05-02-2003, 04:28 AM
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hmmmm i had asked severl diffrent people and they had said that they had never had a hole there.I even looked at my fathers and his did not have this hole. i doubt it was overfilled b/c it has leaked quite a bit and i am doubting i put way to much in b/c i took it back to the tranny shop and they chcked the level and said it was fine out and i know the tranny is mounted where it should be b/c there is no way eles it could be.
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Old 05-02-2003, 04:30 AM
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oh yeah this is what stumps me i had the car in my driveway which is on a hill. it was backed in and then driven in normal. so the tail shaft has been at a lant at one point and it did not leak however when i put it in my garage on level ground is when it strated to leak badly
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Old 05-02-2003, 06:00 AM
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Are you sure it is the from the weep hole and not the rear seal? One other thing it might be is the torque converter. I know for sure the old 50s dual rang hydramatic has a check valve in the fluid coupling that is supposed to keep the fluid in the coupling can and out of the trans case. These check valves always go bad quickly so the fluid fills the case and drips out the weep hole in the yoke like yours does. I know this for sure 'cause mine leaks like that all the time! All you modern tranny experts, do the modern torque coverters have the same check valve feature? Can that thing go bad and cause his problem?

I still contend that weep hole is necessary, other trannys must relieve the hydraulic pressure in the slip joint other ways but it must be relieved some how or there will be huge shock forces on the tranny tail shaft.
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Old 05-02-2003, 11:31 AM
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IMHO- I would recheck rear seal- even a little chafing on the seal area, rough drive shaft yoke,rust etc. has caused many leaks in my garage...
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Old 05-02-2003, 02:27 PM
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I agree with Willy...Yhe hole is there so the yoke can slide without a vacuum or pressure. Some yokes have the splines cut to relieve the pressure. I would believe that the leak is likely from the rear seal. Also, I may be starting an arguement, but, just because the yoke fits the shaft, doesn't mean it is right for it. I have seen this problem before. Changing the yoke, even for another one with a hole took care of it. Maybe it is the wear inside of the yoke.
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Old 05-02-2003, 04:19 PM
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I disagree with the pressure theory willy trans has vent for pressure and oil expansion, some trans use vented driveshaft yoke and many did not.
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Old 05-02-2003, 05:23 PM
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The Vented driveshaft yoke must match the Vehicle/Transmission combination, and yoke spline lubrication. Example GMC 4L60 (700R4) . If it is a truck/van the axle will travel up and down considerably and at the same time move the yoke in and out of the trans. This combination has a metal sleeve pressed on the output shaft. Inside the trans behind the extension housing. It has an "o" ring inside it to seal out trans fluid.So you need separate spline lubrication. (grease) Because it is sealed the end of the yoke is vented. On the car Type the splines are lubed by the trans fluid so the yoke must be sealed off to stop oil from comming out.
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Old 05-02-2003, 06:22 PM
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One question I have to ask is why did you have the shaft shortend? That might give some info as to why this is happening.
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Old 05-03-2003, 08:56 AM
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well in my experience if hole is welded up and it still leaks yet it is not the rear seal. just pull driveshaft knock front joint out then knock
the slug out of the yoke, clean the slug and the yoke with brake clean then put jb weld on the slug and a lilbit on the end of the yoke where slug goes. then put it all back together. as for the vent there is a vent in top of the trans case
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Old 05-03-2003, 04:00 PM
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Well HalfOunce... I'm not sure where your experience came from, but don't understand your answer at all. If the hole is welded up and there is still a leak, seems to me that it must be coming from the rear seal. I also don't know what "slug" you are talking about. Most yokes I have delt with had ends welded in.
Airworld...I may have been understood as far as the pressure is concerned. The pressure I was speaking of is inside the yoke from having the shaft siding in and out. That same suction sound you get when something slides in and out of something that fitsw tight. The trans does have a vent for the pressure inside. The yokes sometimes have vent holes in them. I can't help but believe that the rear seal or fluid level are the problem, if it has the correct yoke. Maybe the wrong dipstick?
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Old 05-08-2003, 12:01 PM
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Try to wiggle the drive shaft to check the clearance. If the bushing is worn the drive shaft will wobble and the seal won't be able to do its job. If you cut the D/S to short it will cause the bushing to ware out real fast. You only need about a 1/2" of end play.
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Old 05-09-2003, 12:22 AM
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I agree with the earlier question, "why did you cut the driveshaft," and was it cut to the right length. Too short of a cut could cause the shaft/yoke to "scoot" up and down the splines of the shaft and possibly vibrate against the rear seal in the tranny causing it to leak.

Also, if the shaft was cut I must assume that you either swapped trannys or differentials which could mean that the tranny may not be centered correctly in the car and thus cause the leak in the rear. If it didn't come in the car, then there's a chance is doesn't sit just perfect and could be dumping more fluid to the rear. Even if you're parking it on a hill, perhaps the hill is compensating for the tilt in the tranny by dumping more fluid to the forward end.

Just a few thoughts...

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Old 05-09-2003, 04:10 AM
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Member #8318 is on the right tract. A lot of trans shops do not put this seal in?
Over the years I have had several complaints of leakage at trans yk. I have welded them. epoxyed them & silaconed them.

Last week a friend of mine that has a trans shop built a 350 for me( we traded tranys )I wanted to use my old speedo gears this trany had a metal sleeve that was sealed to the output shaft w/oring inside. The yk actuly slides inside this sleeve this seals the fluied out of the splines.
this was the first one iv`e ever seen. Don`tknow what it is called, but you might check on it.
(inner yk output shaft seal and retainer ??)
Good luck troy
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