The Title says it all. I have a vibration that seems like it can only come from the transmission. It comes in 2nd and 3rd gear,(maybe 1st also but it goes through that rpm too quickly), right around 3000 rpms. It starts at around 2800 to 3100 and under power. Worse right at 3000, according to my tach. Cruising at that speed, it’s barely noticeable but under power, embarrassing. I replaced the u-joints, new trans output bearing and yoke. The only other thing is that it is somehow the splined area of the driveshaft. But like I said, it happens at the same engine speed and I know the driveshaft continues to speed up through the gears.
I don’t know if a weight or something might have come off the torque converter or something else causing the vibration in the drive train. The harmonic balancer is in good shape, not slipped or off the timing marks. In neutral at 3k rpms, I can’t feel a vibration but it isn’t under a load.
So, unless I hear differently, because I surely don’t want to pull the tranny, I will have to pull it.
Yes you can pull the transmission without removing the engine. I did that a couple of weeks ago- but I wouldn’t rush into doing that just yet.If your converter is no longer balanced, you don’t need to be moving at all. Revving the engine will tell you, and you say that at 3K rpm in neutral there is no vibration. Your best clue is “under power”. Follow that lead. Are the U joints at each end of your driveshaft lined up properly?
I have had a cracked flex plate before that did not show up stationary but showed similar symptoms to you while moving. It was not in jag but would still apply.
Something else you could try is going over the rear suspension/ differential/cage area with a pry-bar to make sure nothing is loose and is shifting when you are “under power”. Engine mounts ok?
Thanks for all the replies. I did pull the rear end a while back and replace the mounts, u-joints, rebuilt the brakes and put in a new front differential seal. It is in there solid. I did replace the u-joints on the drive shaft. When I first pulled it out, I noticed that someone had been into it before and marked the splines one tooth off. I re-aligned the splines to line up the u-joints and it didn’t make a difference in the vibration. I had written about this before here. I thought that was weird but in either position something still causes a vibration. There is a shop that maybe can check it for balance and should have checked that out earlier.
If I am cruising at, I think around almost 70 and step on the gas, at 3k rpms it is very noticeable. Like I mentioned, I put in a new front yoke on the drive shaft and a new tail shaft bushing. The trans mount has new rubber and is free. The engine mounts are new as well.
So yes, the vibration is while under power and seems to be a harmonic since it only shows up around 3k rpm. My ECU is being checked with Roger at AJ6 Engineering and should get it back soon. I will try the in neutral check again just to makes sure if there is a vibration with no stress on the power train. I would know if the engine was missing at that rpm too to cause a miss that could be diagnosed as a vibration.
I did meet a guy at a transmission shop that said he had a solid drive shaft made for a few jags with the turbo 400 trans and just had to remove about an inch of spline at the yoke. A yoke that isn’t threaded into the output shaft. Just make that the slip joint instead of the splines in the middle. To take the middle splines of the drive shaft out of the equation.
Thanks for the replies. I appreciate knowing that I can remove the tranny but will hold off to make sure I can’t find another cause.
Russ
Kirbert
(Author of the Book, former owner of an '83 XJ-S H.E.)
8
I hate fiddling with drive shafts. When the one in my GT6 was messed up, I found there wasn’t an outfit in the state of Florida who knew jack #$%^& about balancing drive shafts. A lot of them claimed they did, but they were clueless. I hope the situation has gotten better in the meantime.
Obviously, if the vibration exists when standing still in neutral, it’s not the drive shaft. If it doesn’t exist unless the car is moving, I’d almost bet that’s the problem – and good luck getting it sorted. Might be easier to just buy a secondhand drive shaft from a junkyard.
I don’t think there are any cars older than 90’s in the junkyards around here. I am pretty sure I have never seen a Jaguar in fact down here. Too bad Jaguar never made a pickup truck, the yards here love their pickups! We have one place basically, a clutch and driveshaft place that has been said to be able to do a good job. Will try them when I can put the car on the lift. Which is another topic that I will start in a few minutes. Sorry it took so long to read this.