5 Speed STD GEARBOX failure

[André Breit]

I am relatively new to this forum but I would like to find out if anyone in this sphere, has ever experienced this type of failure on a
1965-1970 Datsun Sports 1600/2000 2000 Transmission Case (5-Speed)

4 Pictures of GB / crack. I hope thse are able to be viewd.

The unit came from an unknown source but looked fine when purchased. it was overhauled but no special treatment given - its STD.
The Assy – Extension< Rear 32130-25500, was refurbished in 2015/6 by an Aust. / Victorian / Datsun Fairlady enthusiast. Verbal advice offered was that it had some alterations carried out on it to improve it.
It was attached to the remaining gearbox portions (which was used and good working order) in 2018 and felt very tight and responsive.
The race car has a competition tail-shaft which has been used since 2012.
July 2022, when inspecting the extension and its parts, due to the failure, it was found that all parts used in, Assy – Extension< Rear 32130-25500, were standard. The pins had worn high into the ARM-CONTROL 32844-25500.
The gearbox mount, is a refurbished nolathane type, purchased in and used in the race car since 2009. The engine mounts are made from the same material and all are still in excellent condition and there are no visible separation from the metal brackets.
The gearbox has been used in a race car since March 2018 and has raced some 65 hours.
During those times the engine has been refreshed twice.

Capture GB SELECTOR pins at 65 hours racing.JPG

Capture of GB Selector wear at 65 hours racing.JPG

Capture of GB CRACK 2.JPG

Capture of GB CRACK 1.JPG

[img2][/img2]

[rwmann]

Did the tail shaft (or drive shaft) take a (big) hit, aft of the mount?

[Bwk2000]

My $0.02 … Assuming there are no obvious signs of impact to the case and you haven’t been dealing with a serious vibration before the failure, I would suspect the crack might be caused by the high speed repetitive flexing of the frame/body (considering where it cracked and since it was being raced). The frame/cross members continually flex which twists the engine and trans mounts - The mounting points on the trans case will be the weakest link. Might of just been bad luck with that particular case.

[redroadster]

The tail / output shaft is the weak link of the trans , under extreme pressure it will bow a lot can happen in 50 + yrs

[twistin]

Check your driveshaft, make sure the u-joints are in phase.
The rear shaft is splined at the slip point and possible it’s not installed right.
*not sure if they have a master spline.

[23yrRebuild]

Check your driveshaft, make sure the u-joints are in phase.
The rear shaft is splined at the slip point and possible it’s not installed right.
*not sure if they have a master spline.

IMHO...that is DEFINITLY worth checking out...if you don't understand what driveshaft / U-Joint "phasing" means....there is a lot of good videos on YouTube, showing what it's about...even if the "phasing" thing is not an issue for your failure, it should be checked and addressed anyway....in my opinion...
Mike