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The mkiv Supra Owners Club

why is the w58 weak


barneybrendan

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I presume the 'safest' diff for the W58 with the best acceleration is the LSD fitted to the SZ-R?

 

It's the crown that's weak. All NA diff's have the same crown and will always have that same weak point regardless of the model it came from.

 

There's no good compromise I'm aware of with the w58, both the diff and the box are weak points. Fitting an auto LSD will lessen the tractive effort on the crown, retains the effort on the box and reduces acceleration.

 

If you want strong, either it's an r154 with auto TT diff or V160/161 with a 3.2 TT diff. Both are expensive unfortunately.

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how much less accelerationare we talking? noticable when compared to an auto box on the same diff?

 

Would the acceleration be the same as a v161 unning with the auto diff?

 

Yes, it will be noticable, but you're comparing apples to oranges.

 

v161 with an auto diff would be a terrible choice, you'd be changing gears every 10 seconds and have high rpm for motorway cruising

 

so the crown on a TT diff (like my GZ) means the w58 is fine to run BPU power. I can't understandwhy this hasn't come out before?

 

It's come up many times, but I think you misunderstand. The w58 is still a risk with BPU power, sometimes they break, sometimes they don't. The auto TT diff will lesson the stress on the diff, but that doesn't change the torque going through the box.

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ahhh, I thought this was pointing to a conclusion that the w58 box with a TT auto diff is a good option when going manual. The actual conclusion is that a a w58 is going to die at some point with TT power but a TT auto diff will make it last longer before it does.

 

I wasn't comparing apples and pears, I was comparing what I have now and what I would have if I put a w58 box in my car to go manual cheaper that a v160/161. :)

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I wasn't comparing apples and pears, I was comparing what I have now and what I would have if I put a w58 box in my car to go manual cheaper that a v160/161. :)

 

On my N/A in readiness for supercharging, I am using a Manualised Hybrid T.T.-N/A auto trans, proven good for 500+bhp and if it does go bang, it can be replaced for £50. :)

Edited by David P (see edit history)
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What makes it good for (however much torque you're seeing at 500hp)?

 

I won't know either until the project is reduced to numbers, just mentioning that a T.T. auto is good for 500 + of both and they are cheap.

 

Back to beefing up a W58...

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How is your auto box manualised? Have you got 4 gears? Who has manualised it and what was the cost?

 

Fancy software box and some steering wheel flappy paddles.

 

Was doing some googling last night about the root cause of W58 failures and it seems theres many, from stripping gears to synchro's so no one failure mode. But I did learn the Mk4 Supra variant of the box is the strongest with a bigger input shaft.

I think it will last fine of you treat it with a bit of sympathy i.e.tons of burn outs, drag starts all the time. If littlenum hasnt trashed his yet theres hope for you all lol.

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The only thing that is worrying me is how much slower the acceleration is.

 

I guess you can do a manual conversion to a w58 and if it breaks...get a new gearbox for £300 approx.

 

Also, if you did a conversion to a w58 and it bust over time, you could replace the gearbox with a v160/161 and everything else is already in place...I think?

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In fairness my W58 didn't fail due to the torque I was asking it to deal with (NA, so what torque??). And its torque that will kill your box, not horsepower.

 

Mine seems to have died due to aggressive down changes (I'm a fan of engine braking) and the problem was probably exacerbated by the fact I'm using the shortest final drive ratio available (4.273) which means the rear wheels are driving the gearbox even harder than normal when decelerating.

 

I don't subscribe to the view that a longer final drive ratio is going to save a W58, from an acceleration point of view, if the torque from the engine is increased. If anything it would kill a box quicker, stress on gears and sharts shaft wear would increase anyway, as the work it has to do is increased under acceleration (bigger mph increase for a change in rpm).

 

It may have a positive effect when it come to down changing alright as the gearbox wouldn't need to recover as many rpm.

 

Thats my read of the situation anyway, but I do think I may have an odd way of looking at things sometimes!

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I am using a tt auto diff on my na-tt(bpu) with 430lbsft of torque going through it and ive had no problems so far (touch wood) I would like to see the difference in acceleration if I put a manual diff on though as the car is by all means not slow lol

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How is your auto box manualised? Have you got 4 gears? Who has manualised it and what was the cost?

 

Yes it has 4 gears, I have hybridised a TT and N/A trans myself using T.T. box, N/A valve bodies and electronics.

The cost was the price of a TT auto box, which can now operate with an N/A ECU or in my case a Suprastick which cost £250 and a tiptronic steering wheel for the flappy buttons.

Edited by David P (see edit history)
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  • 1 year later...

Well my first post I was amazed people had broke them BUT since then I have smashed that gearbox to bits and 2 others so now trying the R154 and so far not to bad although its gone noisy (winey) in most gears its still working fine.

I took all 3 gearbox's apart and it was the lay shaft and input shaft gears that had stripped off.

All mine broke in 3rd gear when the turbo's came on, since going R154 ive also changed to single turbo and pushing a very mild 460hp.

 

Little video of the R154 taking some abuse.

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