I have been trying to solve a trans leak on my car. The leak is at the tail shaft area, mostly when the car sits this time of year. I have done the obvious things, twice. Those included replacing tail shaft seals, bushing, gasket, and the rubber o-ring on the tail shaft. Replaced speedo seals, then replaced the complete speedo housing with a new one. I've replaced the pan gasket. I have decided to replace the slip yoke, even though it seems to have a good fit in the new bushings. It's the only thing that isn't new on that end of the trans. I am having trouble figuring out which yoke is a correct replacement. Here is what I know about what I have as far as my yoke: my yoke is approx. 6.75 inches from u-joint center line to end of yoke, has 31/32 splines that are counter bored. My yoke still has the nylon locks in the grooves, so an internal locking u-joint 3R yoke would be correct. The problem is that nothing matches the length dimensions of my yoke. I know that I can use a hybrid set-up of internal and external locks for the yoke, but again I'm not finding the correct length measurements. I know the transmission is original to my car. I know the rear-end has been changed to an 8.5 inch. I don't know if the drive shaft is original to the car (has external lock on rear u-joint, tabbed pinion yoke). It may have came from the car the rear end was in. Any suggestions, part numbers, etc. for the correct slip yoke would be a big help. Thanks, and sorry for the long winded explanation.
Maybe this will help. http://v8buick.com/index.php?thread...e-on-the-driveshaft-yoke.307033/#post-2550835
Thanks, Larry. I'll have to take a look at it again. I know I have checked for a weep hole before, but I can't recall what I found. Would still like some thoughts on what yoke to use to replace mine.
After looking into the old thread Larry linked, I have found the yoke in my car (GM part #7801551) available as VIC-SY3R-4120 at Northern Drivetrain (http://www.northerndrivetrain.com/product/VIC-SY3R-4120.html) and from The Parts Place as AT5361A (https://www.thepartsplaceinc.com/pr...f-u-joint-to-end-inside-snapring-design/65261)
Just make sure theres no weep hole in the center of the yoke. Our cars dont need one. If there is one, the trans will dump out fluid if the car sits for a few days
Mine started leaking from that weep hole. I took the DS to a trans shop and they welded it shut. No more leak. Problem solved.
Thought I would follow up on this.... No weep hole in my old yoke. No tell-tale fluid "spray" from the plug area of the yoke visible on the floor of the car. The leak was always right on the tail seal, soaking the mount area and most noticeable after being parked for a long period. I bought The Parts Place yoke (via eBay), some new Spicer u-joints (via Amazon), and picked up a new tail shaft seal & trans mount (ATF + rubber = bad). Took the car out weekend before last for about 20-25 miles. Has been parked for about 10 days now and no sign of a leak. The TPP yoke seemed like a quality piece.
If leak returns check the wiring around the electrical plug where it goes into the case........I had 1 leak from there I couldn't find till I replaced it with a other trabs as inthough the case was the issue
I had this same issue. The original yoke I had was a 3R series, 32-spline, 6.75 length, 1.886 OD, 1.75" counterbore and the weep hole had been plugged. I have a TH400 with a shorty tail housing, about 4". When I took it apart I found that the yoke at it's operating placement was not even hitting the o-ring and was short of it by .375". This explains the need for the weep hole to be plugged as it wasn't being sealed by the o-ring. I ordered this one that is 7.5" from Denny's Driveshaft and should be a perfect fit. https://www.dennysdriveshaft.com/p1296_neapco_n3r_3_9131x_transmission_slip_yoke_3r_series_32_splin.html. I also discovered the reason for the weep hole. As I was test fitting my existing yoke (that has the hole plugged) and trying to get it over the o-ring it was impossible to push it on very far. Once that o-ring makes the seal with the yoke air needs to be able to escape. Try pushing down a syringe with your finger plugging the end, its just like that. My advice: make sure to test and measure everything and don't just assume that what was on there before is correct.
Since we are talking about leaky drivetrain components here I have some other tips. These are for the other end of the driveshaft. I also needed a new pinion yoke for the 12-bolt rear end that I am installing. Here is what I learned on that front: The yokes are defined by the u-joint series. These can be either 1310, 1330, 1350, or GM 3R. The GM 3R is what came stock with my vehicle and I assume that holds true for all 68-72 A-bodies. The GM3R pinion yoke is no longer produced, so cannot be obtained anywhere. The solution for this is to buy a 1330 yoke and then use a combo u-joint; half 1330 half 3R. The pinion seal for 12-bolts came in 2 versions; car & truck. The car version is no longer available so anything you find out there is actually for the truck and would be the Timken 8460N. This seal does not actually fit correctly as explained very well in this video at about the 37:30 mark: . The video provides some workarounds but I found a seal that has less depth to it and actually fits correctly. It is the RATech 6109: https://www.amazon.com/Ratech-6109-Pinion-Seal/dp/B001P2D3LK/ Once again: I acquired yoke and u-joints from Denny's Driveshaft.
