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The mkiv Supra Owners Club

Strange behaviour with TRD diff


Homer

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After fitting the TRD 2 way diff it is performing fantastic at lower speeds and hooning around twisties, but today I used it for the first time on the motorway.

 

At higher speeds (over the legal limit, and into 3 digits) the car pulls to the left under full acceleration, then when lifting off it pulls to the right. It's quite noticeable and felt a little unstable in general, more so when lifting off. This was not present when the worn out and noisy open diff was installed. The car is only an NA so we're not talking about a lot of torque here.

 

I am certain it's installed correctly and every bolt is done up to the torque settings in the service manual. Is this normal with a clutch type diff? I think maybe it's showing up something isn't correct somewhere else on the rear of the car. Any ideas or input appreciated.

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Is there a plate pack for each half, ie output shaft, of the diff mate? If so is it possible one side might be binding? Possibly because some friction material has been stripped from a plate and is now hindering normal rotation?

 

That is merely an uneducated guess, the result of a picture I have in my head as to how a plate type diff functions. I could be, and probably am, a mile off.

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Thanks for the replies. To answer a few points:

 

- The diff is fairly old but hasn't covered many miles, it was setup by a pro, there's lots of markings visible where it was setup

- Wheel bearings are fairly new, I'm confident they are in perfect working order

- Wheel alignment has not been done, but I have a Geometry session booked for this Sunday

- normal function of the diff is fine, the clutches seem to be working perfectly though the twisties and it seems to be perfect at lower speeds.

 

One thing that came to mind was that the aero roof was off when I was driving it, could this be a factor? The car does not handle well at all with the roof removed, but that seems the norm with aero supra's.

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One thing that came to mind was that the aero roof was off when I was driving it, could this be a factor? The car does not handle well at all with the roof removed, but that seems the norm with aero supra's.

 

You have more body movement when roof off, but it should be as bad as you describe. I did regular 60-150+ pulls with the roof off last week, and there is almost no difference in straight line acceleration. You feel it on bumpy roads in bends though.

 

My bet is on wheel aligment mate ;)

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You have more body movement when roof off, but it should be as bad as you describe. I did regular 60-150+ pulls with the roof off last week, and there is almost no difference in straight line acceleration. You feel it on bumpy roads in bends though.

 

My bet is on wheel aligment mate ;)

Ah this is why you have no hair:d

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  • 2 weeks later...

Thanks gents. I had the geo done again and it's a little better (kwik fit forgot to do up 3 of the 4 front lower suspension arm bolts :rolleyes: ). Also found out one of the front wheels is buckled quite badly, but I can't believe its that.

 

The trye wear on both rears looks even, and tyre pressures are matched, I check them every week). However they are different brands, so this may well be the cause as a few have mentioned. Once I get the replacement front wheel I'll get some new rear tyres (matching the front ones). Will also check the rear wheels for any buckling. I've not had much luck there, 7 or the 10 stock wheels I've bought so far have not been round.

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I once had a flat spot on a front tyre and it caused the car to pull terribly to one side. I did wheel alignment, changed suspension, checked pressures...nothing. Once I changed the fronts and found the flat spot all was fine. I never would have thought that tyres could make such a difference, cost me a fortune before changing tyres!

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The problem will be at the rear, for absolute sure. Tyre brand, pressure or geo, (and I include something bent in that), or suspension joint / bush wear.

 

Thanks Chris, always good to have your input on this type of issue. I'm sure you're right, no one knows this subject as well as you :) The brands are different and getting near to the legal limit on one side. I'll swap both out for new ones once I get the front wheel sorted out. I did go to the trouble of doing the service manual checks on suspension component wear when I rebuilt the rear subframe. They were all within OEM limits, I'm quite confident it's not an issue with the various rear arms.

 

I once had a flat spot on a front tyre and it caused the car to pull terribly to one side. I did wheel alignment, changed suspension, checked pressures...nothing. Once I changed the fronts and found the flat spot all was fine. I never would have thought that tyres could make such a difference, cost me a fortune before changing tyres!

 

Thanks Jon, As mentioned above I'll get that wheel replaced before replacing the rear tyre's and see how it goes :)

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In that case just be sure to do it in the dry :D

 

Hehe, no sh*t :) It'd make an "interesting" driving experience in the wet

 

It'll be OK if you keep the speed down, long term.

 

It'd only be for one run, in the dry. No way would I do that permanently. I value my life :)

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