Moss Motors, Ltd

are there any problems or changes I need to be aware of. Thanks

Other than having to get used to that nasty synchro in 1st gear you should have no issues.    Plug and play.

My own TR3A runs a Stag gearbox with TR6 'A' type overdrive, so no problems with the fitment.

The TR4A transmission is one synchro mesh ring longer than a TR3A gearbox. (4 synchro as opposed to 3 synchro)

This means that the gearbox mounting is about 3/8" too far forward on your TR3A chassis when you put in the TR4A 'box.

Do not push the engine forward, relieve the holes in the chassis cross plate.

**File the two big holes in the chassis mount plate rearwards to accommodate this and use big diameter washers on the studs from underneath.**

The 3 studs at the top of the engine are too short for the TR4A gearbox as the bellhousing flange is thicker on the later 'box.

**Change for longer studs.**

TR3A gearbox has a dip stick filler in the top cover.  The TR4A gearbox has not and is filled by a left hand side oil filler hole. I have always found this side filler to be a pain to get at on the TR3A. Be sure the plug is easy to remove. 

**Be sure that the side filler hole screwed plug is able to be removed before the gearbox is fitted.**

**Best mod is drill the TR4A top cover to accept the TR3A dipstick. (the moulding mark is on the TR4A top cover). - but not essential.**

 

Cheers

Peter W

Pete,

I don't have one to look over, but couldn't one make a hole in the gearbox tunnel that would accept a rubber plug cover, and be large enough for access? Or, is the location someplace that wouldn't accomodate this?

Bill

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Motorbill
From Lola to Land Rover, If it's British and has wheels, it's likely I've bloodied me knuckles thereupon

Yes a hole could be pierced in the trans cover.

 

I forgot to add that the clutch release bearing carrier and release bearing assy are different on the TR2/3/4 with a spring type clutch, compared to the diaphragm clutch on TR4A/5/250/6, (Stag is different again as is Dolomite Sprint as is Triumph 2000/2.5pi sedan A nice mix and match game when you get a transmission from an unknown source)

If you are using the orig TR3 type clutch assy just fit the release bearing and carrier from the old TR3 three synchro box.