GREY Crash Box upgrade to HR internals

Includes clutch, transmission, propeller shaft,
universal joints, differential and rear axle.

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FJWALLY
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GREY Crash Box upgrade to HR internals

Post by FJWALLY »

As discussed elsewhere it has been established that the Internals from a later model Red motor gearbox - ie HR gears can be retro fitted into the FB EK gear box housing to provide a stronger gear set.

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EK283
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Re: GREY Crash Box upgrade to HR internals

Post by EK283 »

I will try and catch up with the guy we did the gearset many years ago and see if he can remember what we did.

The gearbox is still in the car as far as I know but it was done over 10 years ago so may be a bit scratchy but I'm sure well work it out.

Greg
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FJWALLY
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Re: GREY Crash Box upgrade to HR internals

Post by FJWALLY »

From Rob

The red motor input shaft is longer than the grey motor input shaft, so they won't interchange.
The red motor mainshaft is probably longer than the grey mainshaft, the speedo drive gear is further forward on the red mainshaft than on the grey mainshaft, and the main bearing snap ring groove is in a different relative position. So the mainshafts don't interchange.
The grey 1st-reverse sliding gear has a collar and groove on it for the shifter yoke to engage into. On the red 1st-reverse sliding gear, the collar and groove are deleted, and the red shifter yoke has two "fingers" to engage the gear. A red 1st-reverse gear won't work in a grey gearbox, because the grey shifter yoke can't grab onto it.
EJ/early EH second speed gears may be the same as the grey motor second speed gear; but late EH-HK second speed gears were revised with slightly different dimensions.
The red motor synchro hub will probably not mate with a grey mainshaft, because of different spline dimensions. And if you could, there'd be no point, because the red synchro hub is designed to be compatible with the red input shaft and mainshaft.
The outer splines on a red synchro hub and 1st-reverse gear have subtly different dimensions from their grey equivalents, so you can't fit a grey 1st-reverse gear to a red synchro hub and vice-versa.
You might be able to fit a red cluster gear and shaft to a grey gearbox if you get the cluster shaft bores machined out to take the red cluster shaft.
As far as I know, the red and grey reverse idler gears interchange.

So I think that the only "red" components that can be adapted to a grey gearbox are the cluster gear, shaft and needle rollers.
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FJWALLY
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Re: GREY Crash Box upgrade to HR internals

Post by FJWALLY »

from Harv

I've never tried to reverse-engineer red motor guts into a grey crashie by modification, but I have tried to put standard red motor bits in (interchange).

The following red motor bits are interchangeable with a grey motor crashbox:
Countershaft needle roller bearings and counter gear retaining ball
Clutch gear bearing
Synchro cone retaining ring, cone and spring
Mainshaft second speed gear (though these changed in HDs),
thrust washer and lock ring
First and reverse sliding gear (though these changed in EH)
Reverse idler gear, shaft, pin and thrust washer
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FJWALLY
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Re: GREY Crash Box upgrade to HR internals

Post by FJWALLY »

The 'red motor' cluster gears take 20 needle rollers (cf. 19 for the grey gearboxes), and the needle rollers are longer than for the greys. The "red" cluster gear shaft is larger diameter. You'd be able to machine out a grey transmission case to take the larger diameter cluster gear shaft.
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Re: GREY Crash Box upgrade to HR internals

Post by FJWALLY »

The crashbox was re-engineered for the EJ, with a longer input shaft, a higher capacity single-row rear bearing, a press-fitted speedo drive gear, and an enlarged cluster gear shaft with twenty needle rollers. The rear main bearing was now retained very securely between the transmission case and the rear extension housing. But the method of location for the input shaft and bearing was a shocker - a Belleville washer between the bearing outer race and the throwout bearing sleeve, which was all held in place by the transmission-to-bellhousing bolts.

The EJ transmission case was carried over for the EH 149, but with new bellhousing (minus "ears" for the grey engine mounts) and new rear extension housing (enlarged, and with pad for red rear engine mount). For the 179 manuals, the transmission case and bellhousing were redesigned, with wider bolt spacing. The clutch was upgraded, and the slave cylinder redesigned with offset bolt holes. I don't know if the S4s had their own "sui generis" transmission cases and bellhousings.

The design shortcomings of the Belleville washer to retain the input shaft soon became apparent. If the washer cracked, the input shaft was now free to move axially. And if you should take off hard at the lights, shift into second, and then floor it, the input shaft would move forwards, the synchro hub and second speed gear rearwards, and a gap would open up between the input shaft and the mainshaft, just big enough to suck the top gear synchro cone dogs into. This would produce a momentary "grrr" sound as the synchro cone machined a couple of millimetres off the splines off the input shaft and the mainshaft. Gearbox now good for the bin.

And so GMH redesigned the input shaft, synchro hub, mainshaft, 1st-reverse gear and second speed gear with revised dimensions to ensure that the top gear synchro cone could not get crunched up if the Belleville washer broke. I think this change happened some time during EH. You can identify the parts in question by a small groove machined onto the splines (usually). The spline dimensions were changed so you couldn't mate "early" and "late" gearbox components.
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