Aluminium case, tail and bell housing

[mark030358]

So after fitting a lotus 5 speed to my Speint what is rather obvious is the weight. It’s probably 3 times heavier than the 4 speed. So I was thinking to maybe have it rebuilt with aluminium case, tail and bell housing.

Apart from the cost of the parts are there any draw backs in terms of reliability/wear in doing this and the big question are the after market parts of sufficient quality and tolerance.

Anyone gone this route?

Cheers
Mark

[rgh0]

Lotus 5 speed is already all aluminium

cheers
Rohan

[Mazzini]

I'm surprised by your comment. I haven't weighed them, but I'd have thought the all alloy Lotus box is lighter than the iron cased Ford box. If I can borrow a big set of scales I'll weigh them.

Update - I used a set of old bathroom scales and the 5 speed box with bellhousing, but without gearlever and clutch fork weighed 26kg. The Ford Lotus box with bellhousing and clutch fork weighted 36kg. These are very approximate weights.

Mark are you using a Voigt gearbox? They have cast main cases and weigh significantly more.

[mark030358]

Sorry my typo error, I was on my way to work this morning. I should have said…..

The 5 speed is about two or three times lighter than the 4 speed

Cheers

[mikealdren]

And, as Rohan says, it already has aluminium housings.

[rgh0]

HI Mark

So you're talking about rebuilding the 4 speed with alloy components replacing the standard cast iron ones?

In general the bearing fits need to be a little tighter to ensure they don't come loose with the greater expansion compared to cast iron. Enough of them have been used in racing to iron out any bugs I would have thought.

cheers
Rohan

[Elanman68]

Had my gearbox rebuilt by Al (Promoter) earlier this year and very pleased with that. However, we did have issues with the parts supplied from one of the usual sources. I retained the cast iron gearbox case but went for a aluminium tail shaft case and bell housing. Fitting the prop shaft bush into the tail shaft housing was the first issue as it just dropped in where it should be an interference fit. There was also a general lack of ‘roundness’ of the supplied bronze bush and where it fitted in the tail shaft case. The 2 components may have been within their individual tolerances but they were at best at the opposite ends of their respective tolerances and not useable as supplied. The prop shaft bush was also too long and under no circumstances could the prop shaft oil seal be fitted.

Al’s fastidious care and attention to detail measuring everything with great accuracy made dealing with the supplier easy and in fairness to them they promptly and willingly sent replacement parts directly to Al which proved to be ok. When I returned the originally supplied tail shaft case and prop shaft bush to the supplier in person and demonstrated the issue they were surprised.

I fitted the aluminium bell housing myself once I had the gearbox back and it fouled the starter ring gear along the lower inside edge of the bell housing. The aluminium bell housing is a thicker casting than the cast iron version. I reduced the wall thickness of the aluminium casting with a small grinder, guided by the witness marks left by the ring gear. I didn’t run or crank the engine whilst it was fouling, only turned it by hand.

The so what of all of this is that sometimes pattern parts that should fit without a problem don’t (I’ve had and continue to have issues with parts that don’t fit as supplied). So measure carefully, test fit and be prepared at best to ‘fettle’ and at worst seek a replacement. In my recent experience the quality control of the supplied parts is variable at best and at worst non existent.

[RichardHawkins]

Not entirely relevant, but I bought a new fuel gauge sender earlier this year, and it fitted! I can’t remember this happening before, most parts I buy are poor and can be altered, or are so bad they are useless. As a friend said, “ don’t throw anything away, you may need it as a sample”.

Richard Hawkins

[mark030358]

I’ll give it a miss I think based on the fact that tolerances are poor.

Thanks for all the comments
Mark

[mikealdren]

Not entirely relevant, but I bought a new fuel gauge sender earlier this year, and it fitted! I can’t remember this happening before, most parts I buy are poor and can be altered, or are so bad they are useless. As a friend said, “ don’t throw anything away, you may need it as a sample”.

Richard Hawkins

How I agree, I have had several similar issues with my Zetec rebuild. It's sad that after market suppliers are often to shoddy.

Mind you, quality generally wasn't very good in the '60s and '70s motor industry when our cars were built and we are getting used to our modern close tolerance cars and, especially, the motor racing industry.