Not quite what we had in mind!

[Peter and Sandra]

Well our three week trip out into the Great Victoria Desert doing volunteer work with the Friends of the GVD came to an abrupt halt when the torque converter cracked. Fellow travellers flat towed us 200km back to Oak Valley community where a tilt tray picked us up.Won't go into the cost of that trip!
We and the Oka are now in Adelaide camped in the Wrights (Oka196) shed removing the transmission to actually see what has failed and chase up repair options.
It is looking like a trip back east to pick up the ute and spare tranny and driving back at the moment, problem is that this is the second time it has done this and we and the transmission bods are at a loss to explain it.

[T1 Terry]

What part of the torque converter cracks Peter? The drag cars have problems with torque cracking so the impeller blades are welded to the case to strengthen it. The crank has a spigot that matches the boss on the torque converter, I've seen those torn out and caused by the flex plate flexing more than it should, a thicker material unit generally fixes that problem. Snapping the torque converter snout is either misalignment or worn rear main bearing shells, the torque converter support bush tells the story as to which one caused the failure, wear one side but not the others is misalignment but oval wear top and bottom is rear main bearing.

[BruceS]

Glenn Cameron in Kingston is the one to talk to.
He's been through it all over the years in his toy tractors!
http://www.austractorpull.com/pulling-c ... -modified/

[Dot]

Up in the Belair area hey Peter, wonder Peter didn't have the answers for you.xx

[BruceS]

Lovely area up there Dot........
I think Peter's has a gearbox, not an auto.

[supersparky]

Peter, What trans are you using? I think that T1 has got the right diagnosis. Is there an adapter plate involved in this?

[jon_d]

Possibly driving style, on and off the accelerator which causes the plate to 'stretch and relax' as it accelerates and decelerates (rotationally).


A classic example was the big ferris wheel in Melbourne. As the wheel turned, the changing direction of weight literally ripped it apart.

[Peter and Sandra]

It is a 4L80E behind a Cummins 6BT using a Destroked adapter. The tranny is rated to far more than what we are putting through it too. It's done over 60k since initial installation behind the Perkins.
It appears to have been a failure of the weld where the stem/snout meets the converter case, no cracks but a pinhole where the weld stops and starts.
No weird wear marks and the flexplate has been dialled and runs true. The bush in the front of the tranny is fine too. Everything lines up well and goes together and comes apart freely, most bolts can be inserted fully by hand and just tightened at the end so nothing has to be forced or "adjusted to make it fit.
There was also a weird rattling noise coming from the inside of the converter at idle sometimes which started a day or so before the failure.
Yes Peter's Oka still has the manual box and Perkins engine.
The torque converter bloke we have found in Adelaide is very knowledgeable and does them for the tractorpullers so we will find out more when he opens it up tomorrow.
Jon the "flexplate" in this case is at its thinnest point about 5mm thick and would be at least 10mm in the centre where it sits on the crank.

[supersparky]

Sounds to me like a failed weld. If it sounds like you have straight cut timing gears when it is running then you will have water trapped in the converter and it will need to be replaced. Does it have a trans cooler running through the radiator? Otherwise I would be looking at a slightly off centre adaptor plate. Are any of the bolts broken?? If there is no damage to the trans then you have got off rather lightly and another converter should not cost the world. It may be a good idea to replace the front seal in the trans while you are having a play in that area anyway.
Good luck.

[T1 Terry]

Failed welds are common when high torque is involved, remember the trans was built for a petrol engine not a turbo diesel engine, horsepower and torque are very different things. My guess and it is only that, a guess, the adapter plate and bell housing has enough movement in high torque situations to cause flexing on the joint between the snout and the converter housing. A die check will most likely reveal a crack through the weld or beside the weld, I think there is a special billet converter housing available but I'm still not confident that the stress will not fracture that either.
In the busses we had dowel pins between each bolt hole that passed through the bell housing, adapter plate and deep into the block to keep everything aligned, we still has torque converter failures but far less frequent