[Fot] TR4 High speed driveline vibration

[toodamnfunky at comcast.net]

OK, 
I got it. The engine mounts are good but I may have a little movement in the trans mount. 
I'm glad you brought it up and I'll check it. 
jim 

----- Original Message -----

From: "Duncan Charlton" <duncan.charlton54 at gmail.com> 
To: toodamnfunky at comcast.net 
Cc: "fot" <fot at autox.team.net> 
Sent: Monday, June 15, 2015 4:13:44 PM 
Subject: Re: [Fot] TR4 High speed driveline vibration 

Hi Jim, 

I don’t mean high loads as in high side loads generated by cornering, which, as you imply, could cock the motor and gearbox a bit to one side.   What I mean is that in top gear, as you approach the point where the amount of drag equals the amount of power available, the driveline is absorbing maximum power and the mounts mounts are providing maximum resistance to the engine’s torque reaction.  The motor/gearbox might cock a bit even in a straight line, I think. 

Duncan 




On Jun 15, 2015, at 2:32 PM, toodamnfunky at comcast.net wrote: 

Thanks Duncan but I never get the vibration under high loads like coming off a corner, it's only at top speed. 
However the trans mount is worth looking in to. I'll have the driveshaft out to a shop by next Monday to check the balance and install new u-joints 
just in case. I hope the problem is that or the trans mount.  
  
jim 

----- Original Message -----

From: "Duncan Charlton" < duncan.charlton54 at gmail.com > 
To: toodamnfunky at comcast.net 
Cc: "fot" <fot at autox.team.net> 
Sent: Monday, June 15, 2015 1:13:33 PM 
Subject: Re: [Fot] TR4 High speed driveline vibration 

Jim, 

How are your motor and trans mounts?  If they allow the engine/gearbox combo to shift out of line when under high torque, the u-joints could move out of proper alignment, but then when power is reduced, things would shift back into position.  If you put the car on jackstands and run it to this rpm in top gear (might not be a bad idea to remove the drive wheels and tires if you’re sure they’re balanced) there won’t be much load on the engine, so if the vibration is due to deformation of the mounts, the vibration should not appear. 

Duncan 



<blockquote>

On Jun 15, 2015, at 10:55 AM, toodamnfunky at comcast.net wrote: 

FoT, 
I have a driveline vibration that doesn't start up until I get to about 95- 100 MPH. I figured I would start with the driveshaft 
before looking into the diff or OD/trans. I have an IRS car with Richard Good CV axles and hubs so it's very un likely its that but 
I will inspect them. I'm wondering if anybody has any advice on high speed vibration diagnosis or detection. 
What I'm wondering is even if it is the driveshaft how would I know with it sitting on my bench. 
Any help would, as always be greatly appreciated. 
Jim g 
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