R12 5 speed

S

Stuey

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Fellow Frogger
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Location
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Hi all,

Is there a five speed conversion for a stock engined R12 that's worth doing? The reason I ask is that I phoned a guy selling a fully worked over 12 here in WA a while back which had a 5 speed (other spec being 4 wheel discs, twin Webers on a 16 motor, Konis and a load of other stuff) and even though he was selling the car he reckoned the stock 4 speed was better. Frankly, I reckon the stock ratios are absolutely spot on for city driving too, but a 5th that gave just over 1:1 would be ideal. All comments gratefully received :D

Stuey
 
I've always liked the idea of the 365 17TS/G five speed, with the stock 12 1.3/1.4 motor it isn't as overgeared as the 395 18 gearbox. Only problem would be is to find one! I have heard of a 395 being installed into a 1.4 Virage, and the owner reckoned it was brilliant, but I still don't like how the 395 gearing looks on paper with the characteristics of the 12 motors.

Standard 12 ratios
Diff Ratio 3.778:1 (9 x 34)
1st 3.818 7.15 km/h
2nd 2.235 12.22 km/h
3rd 1.478 18.48 km/h
4th 1.036 26.37 km/h

17TS/G 365 ratios
Diff Ratio 3.77:1 (9x34)
1st 3.62 7.9 km/h
2nd 2.34 12.3 km/h
3rd 1.61 17.8 km/h
4th 1.22 23.6 km/h
5th 0.94 30.7 km/h

395 5 speed ratios
Diff Ratio 3.778:1 (9x34)
1st 3.818 7.32 km/h
2nd 2.235 12.51 km/h
3rd 1.478 18.91 km/h
4th 1.036 26.99 km/h
5th 0.861 32.46 km/h

Mind you the 1.4 engined 12 would fly if the torque would let it pull top ratio of the 395! Fifth just seems to high for practical use. The closer ratios of the 365 though seem just about right, and fill the gap between 2nd and 3rd of the stock 12 four speed.

Even the AUS 12G works rally cars were considered over geared for their particular purpose, lower ratio diff's being preferred. The works 16TS rally car also seems to have been fitted with 13" rims as an experiment in order to lower the overall gearing so it was obviously a known problem. On the open road though, with the 1565 motor, the 395 ratios are probably just about right for an everyday road car.
 
Yeah, that's what I thought; the 395 5th is too high. The 12 could only manage a slightly overdriven 5th. It'd be the perfect solution with something like a 0.95 top. Simon, I assume that your km/h per 1000rpm figures are different between the R12 and 395 box because of wheel size? Oh, and the 395's a straight fit, isn't it?

Thanks for the info.

Stuey

<small>[ 05 January 2003, 02:38 PM: Message edited by: Stuey ]</small>
 
Hi Stuey,

If you want to frig around with a 5 speed conversion, how much harder would it be to drop in the motor and tranny from an 18 or couple the 5 speed box to a 17 or 15TS motor while the car is apart and drop the lot in.

I have a few bits and pieces lying around the place and would like to have a go at this but just don't seem to get around to it.

cheers!
 
Ha Ha. Don't laugh...I towed a 6'x4' full of concrete slabs once. It was like the QE II - no stoppin' her. Luckily there were no red light cameras...

Smokin' !!

Stuey
 
Go nuts - bolt in a Fuego 2 litre OHC alloy engine and box and give the idiots in their V8 Holdens a shock...... dance
 
It is surprising what a stock 12 will do, mine has towed a car trailer mit R8 (less engine and windows) up through the old Devils Elbow and return about twice, apart from being a bit slow up the incline I thought it performwed the job quite well.

As for upsetting people in Holdens, it used to do that regularly anyway, and when I was at school. Now I've been told "to show the old girl some respect" though......
 
It is true about the surprising abilities of that great little Sierra motor. I had a couple of R10s (same motor, just a little smaller) and they were absolutely unkillable. Started driving one with a big end noise, and 6 months later of hard city driving (the rev limiter is simply when valve bounce kicks in and it stops making power....), and runs to my parents in the country - two hours of about 4500rpm. Still ran perfectly, until an air cleaner mounting stud and nut fell into the carby - stud went into no.1, and the nut went into no. 3. Made a good noise as the liners cracked when the piston tried to go sideways when it couldnt go up!
 
Haakon, when I had mine rebuilt (only because I holed a piston days before I went overseas) the monkey apprentice I assume they put on it forgot to tighten all the oil pump cover bolts. So it was ok for about 30,000 km then I got a big end knock on startup, getting worse and worse. I just assumed they'd stiffed me on the bearings (they had since gone out of business). I dropped the sump, found the problem, and checked the bearings which were unmarked. Tightened it all up - that was well over 50,000 km ago. Still no noises, and I flog it to 6000 regularly. Too bad they didn't replace the valve guides...

Stuey
 
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