SADS question for those who have done it

[scAC]

Hi, about to tackle the SADS on my 1996 S/C Previa for the first time. I have an annoying vibration at idle that I want to get rid of, and close inspection reveals only the rear coupler is finished (torn rubber/excess movement), while the front coupler is nice and tight - no damage to the rubber whatsoever.

My question: am I able to replace just the rear coupler without removing the whole SADS shaft, and then tackle the front coupler at a later time? I ask because, from what I can tell, the front coupler is the difficult one to access, and I'm not sure I have time to do this whole repair with my Nov/Dec work schedule.


In my E39 BMW, you can simply unbolt the guibo/flex disc (similar to previa coupler) from the end of the driveshaft without removing the whole driveshaft from the car.


So ... can the rear coupler simply be unbolted and dropped from underneath the van, with the front of the SADS shaft still fully attached (untouched)?

I appreciate any help/advice!

[pdgizwiz]

My answer to your question is: I doubt it.
But there's no harm in trying, i guess. Just make sure you mark all the parts so that you can assemble them again in the same position. Worst case, you bloody your knuckles finding out that the shaft has to come out after all.
Yes, removing the entire SAD shaft is a PITA. But I see it as a "right of passage" to become a true Previaphile. And sooner or later you'll need to replace the front coupling anyway,
And I have an e39 also!

[TCR10]

Hello. I've replaced the couplers on my Previa's Equipment Drive Shaft. I pulled everything out of the way and mostly followed the FSM procedure. It was complex, challenging and rewarding. I don't think there is any way to remove the rear coupler because it has three bolts that insert from the rear that do not have clearance to remove. Also, the coupler itself has steel bushings that insert tightly into bores that would prevent dropping it out. Good luck with your project.

[samstrader]

If you try it, just remember that you are not supposed to let the back of the shaft drop or move sideways much at all because if you do, you risk damaging the front coupling. You will have to support the shaft well enough to ensure it won't drop down while you are working on changing the coupling.

I'm surprised only one coupling has gone bad. Every time I have changed my couplings, both couplings were bad. I think I have changed mine 4 times now but actually have lost count.

This last time I replaced the couplings, I installed the BMW drive shaft couplings according to the procedure from this forum and they have been working very well for about a year. I don't see how they can ever fail but time will tell.

[man_btc]

I found this youtube video that may be what you're looking for. However, keep in mind you may be seriously stressing some old rubber mounts on the front part, and placing your hand and fingers in danger if the clamp-and-bar jig lets go or slips.
https://youtu.be/zYdIaxPnhcE

I wouldn't even think about it unless there was a way to place some wood or something as an extra backup wedge, but then I'm the type that slides two 2x3 landscape-timber blocks under the van in addition to the jackstands before I put my face under there...

[man_btc]

Another thought - you should see if the rubber (between the inner and outer parts) in your harmonic balancer has begun to fail, making it not-so-balanced and perhaps putting extra stress on that rear coupler. I'm still on my original HB, but noticed that the one on my Arizona-sourced '91 looked bad, with the outer and inner parts displaced relative to each other. Having only driven it onto and off a trailer for maybe 300 feet I can't speak to any noticeable vibrations. In general my winters-in-the-Northeast '92 has relatively good plastic and rubber but bad rust and the AZ van has little rust but the plastic and rubber are more hard and brittle.