So here I am again. Just trailered back from VA with my Saab in tow, and she ran like a champ the whole way. Took her to drop off the trailer at U-Haul and as soon as I unloaded her, she started with a horrific vibration under load-enough to shake the gauge cluster bezel around and release the steering wheel latch. It's absolutely impossible to go over 30-35MPH with her right now-motor isn't missing and seems perfectly fine. Had to get a new transfer case put in while I was in VA-blew up the last one. Believe this is drive shafts but they seem to be fairly solid. Haven't gotten to dig to her in yet so wanted opinions...know they were in and out like crazy setting up the TC etc. just seems odd it came up after I drove 1200 mi without issue and after I removed the weight.
To describe the vibration-I would say its a bit like driving high speed on a very choppy gravel track. Whole interior rattles and squeaks about.

 

Does it correspond with speed?

 

yes-almost nothing until about 15 mph and the higher the speed gets, the more it tries to shake my internal organs out.

 

Rubber flex coupler disk at end of rear drive shaft - look for cracks.

Drive shaft out of balance bad, could remove one or the other and lock CDL to drive and test, don't cut donuts.

Suspension was compressed, is it now allowing something to touch where it shouldn't? Mechanic tool or clamp or block or spacer left somewhere by accident? If you put 400 pounds in the back does it go away (mother in law, bags of cement, etc. - something to equal tongue weight)?

Then you get into things associated with Death Wobble, but usually not at such a low speed...

 

You may have a bubble on one of your rear tires as a result of towing especially if you used a 2 wheel tow dolly. This happened to me after towing my MB 300d donor vehicle for my diesel conversion. Motor alone in that car is about 600lbs. GVW is 4200lbs.

Once I returned the trailer, I noticed coming to a 10mph roll there was a bit of a wobble as if one of my tires were going over a soft bump... only one tire and hitting the same bump with each revolution.

I parked the truck and noticed a lump in my tire. Just a thought

Agreed with BUZZ on the death wobble components though. those flex plates take quite a bit of twisting as the drive train adjusts for towing weight. punishment on drivetrain will slop out rubber components on their way out. Otherwise regular in town driving you will never see that kind of abrupt failure.

 

Check your flex coupler, thats almost exactly what mine felt like when it went out. Just all of the sudden gave up and the guy I got my Disco from had replaced it less than 1k miles before it went bad.

 

Spark plugs? Mine would shudder just as you described, and it is usually a sign of spark plugs going bad.

 

Well, I checked the tyres and there seems to be nothing to report there-they need replaced but for no other reason than they have some dry rot (facepalm to Michelin and their SUPER hard tyres) and there appear to be no bubbles. I replaced the plugs recently and that was a first thought but it's running great and a CEL would come on, would it not? I am dreading getting under the car right now-its 110 degrees and every time I go out I come straight back in! I will check the flex coupler and all of that in a couple hours as well as removing the front driveshaft to test it out. If it is a driveshaft-how should I go about replacing it? I don't really want to rebuild it if it's the front one-I'd quite like to replace it with a proper double cardan shaft. I saw one at one point but forgot where it was from. Some heavy duty serviceable unit...I'd like to replace it with one that I won't have to worry about in the future. I have replaced most everything in the powertrain so far-so I want it to be right. then next up comes the TVR 5.0 engine swap....
EDIT: just checked under the truck and maybe I'm retarded but I don't see any flex couplers on her at all....nothing between the driveshaft and the rear or front diffs or on the transfer case ends....I feel like that could be an issue. Are they sandwiched between all ends? Again might be retarded buuuuuuut that doesn't seem right to me.

 

What year is your D1? Only certain years had the rotoflex, and sometimes even years that came with the rotoflex have already been changed out. So if you don't see the black rubber donut just in front of the rear diff, count yourself lucky.

Is your truck lifted? If not then you'll probably be fine with the stock one and maybe just a rebuild. They're really easy to rebuild. About $20 for two ujoints and 45 minutes and you'll have a rebuilt shaft.
If you go with a DC front shaft.......... RUN away from any driveshaft mentioned on this board. I think most of those threads have been deleted anyways. Go with a Tom Woods and be done with it. Or you could go with a D2 front shaft rebuilt with servicable joints and a D2 Transfer Case flange. But usually by the time you add all that up plus the work to do it, its easier to just buy a Woods.

 

I have a VERY late '99 D1-build date 5/99. It has no donut on it and I bought it with a 3in. OME lift. I have a feeling the front is gone. I was looking at the Tom Woods-is it pretty much a plug and play thing? Is there any mods that I need to do to get it in there?