| Author | Message | ||
     Randy Roberson Grand Master Username: wascator Post Number: 362 Registered: 5-2009 |
Hi, I drove a '77 Wraith II home from an auction for a buddy (340 miles: egad, but we made it fine, and I had a chase car, too). Only weird problem I could find: on a heavier pull than normal cruising, as a hill, a vibration would appear suddenly, almost like a shudder. Back off the throttle and it went away. I thought first, the Michelin Symmetry tires were letting go (they are old) but they made the trip. Then I thought: engine miss. The fuel mileage was averaging a little over 13 MPG (this is a USA model, and a US gallon, remember). What do you think? I thought of engine mounts; U-joints; differential mounting; rear axles. absolutely no clunk or other loose feeling, and it tracked very straight, actually a joy to drive and very comfortable. Very nice car showing 52,000 miles, with a few maintenance items to soon be caught up. | ||
| Brian Vogel Grand Master Username: guyslp Post Number: 1277 Registered: 6-2009 |
Could it be the Detroit joints? These are often blamed for vibration through a limited speed & pull range. It's said you can swap from side to side to get new wear surfaces if this trick has not already been done before. Of course, I'd definitely check a lot more of the usual suspects related to tires and wheels before even considering this. It sounds like that will need to be done anyway. Brian | ||
| Vladimir Ivanovich Kirillov Prolific User Username: soviet Post Number: 215 Registered: 2-2013 |
The first thing I would check is the universal joints on the tailshaft and also on the rear axles. Additionally, turn the tailshaft around and look for any dents in it. I had a 1974 Cadillac Fleetwood that was transported from Darwin to Brisbane. When I picked the car up in Brisbane it had this most rude vibration in it that it never had in Darwin and I soon discovered the vandals at the transportation company had lifted it off the truck using a forklift which caused the diff to sag down and creased the tailshaft. If you find yourself a good transporter treat him like a Czar because there are some in that business who should not be permitted to transport wild pigs or politicians. | ||
| Mark Herbstreit Prolific User Username: mark_herbstreit Post Number: 124 Registered: 5-2005 |
Hi Randy, If you search the topic "vibration made worse", you will see I have (and am still) going through this. I definitely had a driveshaft vibration which was more noticeable on undulating roads. As if to complicate things I now have the vibration under load as you describe. This has only manifested itself while chasing the other vibration and I am certain it is ignition. This was proven by strapping a microphone above the exhaust outlet with a speaker inside the car. You can hear the misfire under load. Cap leads coil plugs etc. have all been replaced and I will replace the electronic module next.  I had earlier strapped a camera and lights underneath to watch live what was going on with the driveshafts. This proved to be a bit dark, and normal road vibrations did not give a clear picture of what was going on.  Recently a Turbo R followed me home (Thanks Richard and Omar!), and has been hogging all my spare time. They are great cars and a welcome distraction from the issues of the Shad! | ||
| Geoff Wootton Grand Master Username: dounraey Post Number: 672 Registered: 5-2012 |
I have this problem also, a vibration that starts at 35mph through 45. After that everything is smooth. The problem started after I changed my saggy rear springs. It seems the driveshafts had worn in to the the old ride height making them incompatible with the new ride height. I tried to switch them over, which I thought was going to be a nice simple solution, but the problem is I cannot shift the plate that adjoins the diff casing. I removed the 6 nuts and tapped the edge of the securing plate but it would not budge. It seems to me the only way to free this plate is with a chisel and lump hammer. Since I did not want to risk damaging the diff casing I aborted my attempt at switching the driveshafts. Does anyone know if this is a common problem? Has anyone succeeded in removing this plate and switching their driveshafts? Geoff | ||
| Randy Roberson Grand Master Username: wascator Post Number: 364 Registered: 5-2009 |
I think maybe this is an ignition-related problem. I would describe it as a shudder. Its as a clutch repeatedly catching and slipping. I am not certain but can the TH 400 transmission do this in direct drive (i.e. high or third gear)? The shifts were smooth and the situations were never such that the transmission had to shift to second under load. I just noticed that, below a certain load, as normal crusing, there was no shudder.Forgot about the clutches in the transmission. | ||
| bob uk Unregistered guest Posted From: 188.29.164.124 |
Check the oil level in the detriot pots. Check engine mountings. Check exhaust mountings. (Message approved by david_gore) | ||
| christopher carnley Unregistered guest Posted From: 86.128.43.82 |
If you mean the bearing and oil seal housing,then you will find that it is recessed with an interference fit and very tight. Try heating the main casing, after draining out all the oil, and insert a very thin wedge (chisel) on each side. Mind, it is very tight, and the shaft splines are no slop fit either. (Message approved by david_gore) | ||
| Geoff Wootton Grand Master Username: dounraey Post Number: 673 Registered: 5-2012 |
Hi Chris That's really useful information. I thought it was just a covering plate, not a machined housing. So it appears that this simple job of switching the half shafts is not so simple after all. A while ago Brian Vogel suggested heating the casing but at the time I had a minor petrol leak (now repaired) and didn't fancy being enveloped in a ball of fire. I have to say I'm still a little apprehensive about using flame in the vicinity of the petrol tank, but I guess that's just me being over cautious. I think this job will go back up my todo list, now I understand the nature of the beast. Geoff | ||
| David Gore Moderator Username: david_gore Post Number: 1574 Registered: 4-2003 |
Hi Geoff, An electric hot air gun in a draught-free environment should safely provide enough heat to expand the casing and housing if you are patient. If you quickly cool the housing with a wet cloth/sponge, there should be enough contraction away from the differential case to facilitate removal. | ||
| Geoff Wootton Grand Master Username: dounraey Post Number: 674 Registered: 5-2012 |
Thanks David - I think I will take that advice. Geoff | ||
| bob uk Unregistered guest Posted From: 188.29.165.20 |
If you are windy about the fuel tank. Remove it. Or fill with water. (Message approved by david_gore) | ||
| Benoit Leus Prolific User Username: benoitleus Post Number: 196 Registered: 6-2009 |
When I swapped over the driveshafts on my '79 Shadow I could just take of the bearing housings by hand. Is that normal or should it indeed be a very tight fit as on Geoff's car ? Benoit | ||
| David Gore Moderator Username: david_gore Post Number: 1577 Registered: 4-2003 |
Benoit, I had the same experience with DRH14434, the housings came off of their own accord without needing any "persuasion". When replacing them, I used a 3 stage tightening sequence on diagonally opposite fasteners with a torque wrench: 1. 30% specified torque 2. 70% specified torque 3. 100% specified torque The final diagonal torque is followed by a repeat 100% torque sequentially around the housing. I am very conscientious when tightening steel fasteners into light alloy components as it is easy to damage threads by cross-threading or over-torquing - been there, done that unfortunately but experience is the best teacher........... | ||
| Patrick Lockyer. Grand Master Username: pat_lockyer Post Number: 940 Registered: 9-2004 |
scope it, may be a ht lead going bad. | ||
| Randy Roberson Grand Master Username: wascator Post Number: 371 Registered: 5-2009 |
I think that may be right, thanks! |
