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MG TD TF 1500 - Drive Shaft Alignment?

Hi gang;

This morning I picked up my rear axel which has just been modified with the 4.3 gear ratio. I have completed installation with the exception of the brakes, backer plates, hubs and tires. I decided to run the car on jack stands to make sure that everything is ok before completing the rest of the car. I am getting a vibration when running in this configuration. More correctly it feels like a buzz, noticeable in the pedals and the steering wheel,in fourth gear at 2000 and again around 3500 RPM. I rechecked the bolt up of the driveshaft to input pinion flanges and they were tight. I check for a gap between them and could not insert a .002 feeler gage anywhere around the circumference. I then rotated the flanges 180 degrees (can't rotate 90 degrees due to bolt pattern)and came up with the same result. I believe that my mechanic said that he did a run out of the input pinion flange face but I don't know what the measurements were other than ok.

Does this still sound like driveshaft alignment or could it be a problem with the new gear installation. There are a number of you out there with this modification and someone may have run across the same buzz.

I appreciate any guidance anyone can give me.

Dick
Dick McCutcheon

Was your shaft blaanced? Did you put iat back in the same place, that is mark the place and reinsert there? May be naow out of balance.
Ellis Carlton

Hi gang

The shaft was not removed from the car during the changeover and marking the aft flanges would not have helped as the differential now has a different input pinion flange from the MGA that donated the new gears. There had not been any previous balance problems for six years of operation up to the point of initial runup with the new setup so no reason to suspect shaft balance.

One thought that my mechanic pointed out was that the aft end of the car is presently supported by jack stands under the frame. This means that the aft universal is at it's max working angle due to the weight of the unsupported axel/differential hanging on the lower limit straps. This possibly could lead to a vibration problem. Tomorrow I will move the stands under the axel to see if the problem improves.

Thanks

Dick
Dick McCutcheon

Dick - I don't think that I would panic just yet. As I remember, when I did the same thing with our Magnette that you are doing with the TD, I experienced some vibrations that weren't there when all four wheels were on the ground. With the wheels spinning in free air like they are, any little imperfection is going to show up while they probably won't when you are driving.
Good luck - Dave
David DuBois

Hello Dick. I think the angle deal may be the problem. My 280Z is very sensitive to tire balance so we spin them on the car. If you do the rear with the body jacked up rather than the spring pan (independent at rear with separate u-jointed axles), the car shakes and vibrates like crazy. Also, the axles and wheels damp a lot of vibration. Did you find someone locally to do your change-over? George
George Butz

Hi Gang;

This is my final report. The problem has gone away with the car completed and on the road. So much for paying too much attention to little things some times. If there is anyone out there contemplating the change over I too will give a hearty recommendation for it. In a sentence it makes the car feel less crude. The clutch action in first and reverse is now acceptable and the ability to start out in low without an immediate shift into second is highly desirable. I haven't done any real cruising with the change yet but now I am looking forward to it. I don't know why I waited five years.

George, to answere your question, yes I found someone local. He is the same mechanic that rebuilt my frozen up engine and overhauled my transmission when I restored the car. Although this was the first MGTD transplant for him, he rebuilds engines, transmissions, rear ends and most anything else for SCCA Vintage racing. If anyone local is contemplating the modification they can contact me off line and I will be happy to supply the information.

Safety Fast
Dick
Dick McCutcheon

This thread was discussed between 09/05/2003 and 10/05/2003

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