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1966 TR4A solid axle problem


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Does anyone have any information or experience with solid axle TR4A's that exhibit a "twitch' or yaw to the left during rapid upshifts/downshifts or rapid throttle reductions? I've owned this car for over 15 years and have had it inspected numerous times to no avail. New rear springs and bushings (first rubber, now polyurethane) have been installed, it has had a 4 wheel alignment, lever shocks serviced, no leaks, new Dayton 60 spoke wire wheels (replaced original steel wheels), Michelin 165x15 tires. Yaw does not occur if upshifts/downshifts are accomplished very slowly. Slight yaw if throttle reduction is gradual although it is never consistently the same. Tubes to differential have been inspected as has the entire rear axle. Distance pieces and securing "U" bolts are in good order and secure.

 

Any thoughts on installing front and rear sway bars on this car? Would sway bar installation minimize or in any way reduce or affect this tendency to yaw during rapid throttle reduction?

 

Thank you.

 

RMerrell

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Hi Richard,

 

Isn't this due to the rear axle being driven only on a single side? You could install a posi-traction device, but that seems way overkill. Essentially, all the torque from the engine is only going to one rear wheel. When shifting up/down the sudden drop off/application of torque going to that wheel is most likely what you are feeling. This effect can be compounded a bit with any slack that's built up in the tranny and u-joints (although less so on the solid/rigid axles than on the IRS due to fewer u-joints). This doesn't mean you should rebuild your tranny by the way!

 

As long as your dif, tranny and ujoints are in decent shape, and the shock links and rest of the suspension is not worn, I think you may be experiencing what is just the result of the byproduct of the original design. Others chime in and I may be way off, but the solid rear axle cars are pretty sturdy.

Cheers.....Dan

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Hi Richard

 

I think the twitch is inevitable with a solid rear axle as experienced on our TR4 under hard acceleration.

 

The phenomenon has been viewed by other drivers following our progress on various regulatory rallies.

 

However, just had fitted a rear ARB and that has definitely firmed things up as would an anti tramp bar, if such a thing were available.

 

Sounds as though everything is OK but perhaps the added stiffness of ARB or sway bar will limit the lateral movement.

 

Cheers

 

Darren

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The factory offered torque rods for the rear axle as a racing option for the TR4. That would probably cure the problem. I've never noticed it - maybe just used to it after driving TR4s for many years.

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I am obviously not driving mine hard enough as I have never noticed anything like that although the rear end is set up very firm indeed with four extra clamps on each spring and uprated Armstrongs. Im not sure if the "Deep dish" spring versions are more or less susceptable.

Stuart.

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Does anyone have any information or experience with solid axle TR4A's that exhibit a "twitch' or yaw to the left during rapid upshifts/downshifts or rapid throttle reductions? RMerrell

 

Richard,

 

Have you check the gearbox attachments, especially rear bushing ?

Is the whole engine/ gbox/ axle aligned?

Is the chassis straight?

 

A front sway bar is a very nice improvement. Rear sway bars generally get removed after some time and everybody has a different reason for that. Does not appear very rational. It just seems a useless gadget. I have no personal experience.

 

Cheers,

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Richard,

 

Have you check the gearbox attachments, especially rear bushing ?

Is the whole engine/ gbox/ axle aligned?

Is the chassis straight?

 

A front sway bar is a very nice improvement. Rear sway bars generally get removed after some time and everybody has a different reason for that. Does not appear very rational. It just seems a useless gadget. I have no personal experience.

 

Cheers,

 

Badfrog,

 

Thanks for your comments. I think the problem must be somewhere in the list you provided although to the best of my knowledge, the chassis is straight (never involved in an accident - I'm only the third owner of the car and I know the other two). In the interest of drivability, comfort, and engine life, I'm going to commit TR heresy soon in that I'm going to change out the car's non-overdrive 4 speed for a Toyota Celica 5-speed. It fits perfectly, no cutting or welding and the cockpit remains absolutely stock with no visual clue to the changed transmission. I'll keep the original 4 speed should a future buyer (although I have no intention of ever selling the car) wish to return the car to it's original transmission. With this change (also involving a lightened clutch), I'll address the alignment issues you've mentioned. Thanks again.

 

Regards,

 

Richard

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