SADS question

[f18cmech]

Can someone tell me if polyurethane sads couplers are ok to use? And, what are the symptoms of failure? My Previa has vibration at idle that increases with AC on, headlights on, seems like the more load the more racket coming from the SADS area. Thanks...

[Kurtanius21]

Before you throw money at parts, go ahead and save yourself from risk by inspecting the bushings yourself. Get underneath the van and look at the SADs shaft ends. It will be pretty obvious if your bushings are bad. Look for cracks in the rubber. Try twisting the shaft by hand. Should be little play, elastic if there is no wear. What you describe sounds like SAD problem. How sad.

I have heard some people use the polyurethane bushings with 2+ years without problems. If you plan to keep this van for more than several years, you ought to invest in OEM. If you're just looking for a quick fix for just a few years to hold you over, I wouldn't recommend against it.

What year is yours? If it is older than 93' than make sure you get the right couplers. Old couplers are not compatible with newer previas and vice versa. Unless you have a newer shaft, don't put newer couplers on a 91'-93'.

[f18cmech]

It's a 96. I already saw that the rubber bushings were cracked through and there is some play but not a lot. Can this job be done without taking out the whole shaft? I'm a helicopter mechanic so I'm not too intimidated but who wants to do unnecessary work. If you've done it some advice would be great.

[f18cmech]

You did mention elastic, although the bushings looked cracked the shaft does spring back to place when I give it a twist. Does this mean I have some time before its really time?

[pdgizwiz]

Other than noise, I don't know what catastrophic failure looks like. I'd guess the noise will just get worse until you can't stand it any more.
The guy that put up this video (https://www.youtube.com/watch?v=Q0AiRkVsusA) is a friend of mine, and he's still driving his Previa with the couplings in this sorry state. He has new couplings but hasn't gotten around to installing them yet.

[timsrv]

When you replace them, don't forget to "enhance" them :LOL2:.

https://www.youtube.com/watch?v=DmvIV3cEcag

[zak99b5]

When you replace them, don't forget to "enhance" them :LOL2:.

https://www.youtube.com/watch?v=DmvIV3cEcag
I love that video. The beats really make the difference. 😜

[MariposaWrick]

I am a Newbie DIYer Dad. My question is how long, miles, can one wait before replacing bad SADS components, other than when they completely fail? Son's band uses 1990 Previa for road trips of hundreds to many thousands of miles, last summer. Of course on the eve of leaving today for a trip of 400 plus miles across California into foothills of Sierra he had me listen to rattling noise in front of motor that started to be noticed "after they got back" in August. It is loud rattle at idle but quiets on acceleration and when AC is operated. looking into this forum I believe it has the characteristics of SADS components worn out. One post i saw referred to "glad to know the SADS can wait." The trip today will cover 400 ,miles round trip and go from flatland to 3000 feet, all highway. Does the pattern of rattle at idle and quiet on acceleration sound typical? Is it safe? Will they lose power or driveability if the bushings/cushions fail or just the ability to run AC? Will it affect alternator operation? Thanks for your experienced opinions and advice.

[pdgizwiz]

I've no experience with outright "failure" of the SADS. I expect it would be ugly. What fails first are the rubber bits that surround the small steel tubes bolted to drive flanges of the shaft components, and if that rubber were to go away entirely the steel parts would be rattling around within the aluminum coupling bodies. Eventually, I suppose, the bolts holding the steel tubes would shear off and the shaft would no longer transmit power, so you'd lose the A/C, the alternator, and the power steering. I can only guess that before that happened it the noise would have gone from a rattle to an outright roar. But as I said, I've not experienced this, nor have I read any accounts of such.
A buddy of mine made a long trip with a hammered SADS and lived to tell the tale. He replaced it later. I've owned several Previas and the SADS couplings are usually the third thing I replace, after the valve cover gasket and distributor O-ring.

[MariposaWrick]

Thanks pdgizwiz. I sent my son off on the 400 miles journey. So far they got to the turn-around point halfway. I let them know it is the next thing to be fixed upon return. In their case the noise is a noticeable rattle but not nearly as loud when under power, so I suspect it is at the "rubber bushings going" stage.

Next need to get ahold of OEM bushings and contact a friendly shop for an estimate or an even better friend with a lift and some help doing the job.

This Previa turns out to be a 1992, not '90 as I originally reported.

I appreciate the thoughts. They were encouraging, sort of.