'68 Alfa Romeo Gt Junior
Discussion
VM: heres the drivetrain spec:
The gearbox is not original, it is from a later car and has the higher .79 fifth ratio instead of the 1300's .86. This was fitted with the larger engine, freshly overhauled by Bob Dove and should be no trouble. I do not know what speedometer drive is fitted however. The axle is the original as far as I know and is probably 4.55:1 giving you gearing that is standard for a 1600cc car. The intermediate ratios are the same for all boxes, so you have 1750 spec except for the axle which should be 4.1:1 as standard.
I have a bit of a clunk coming from the diff when the car is moving at slow speed, so will look into this at some point, maybe at the same time upgrading to the 1750 spec.
The gearbox is not original, it is from a later car and has the higher .79 fifth ratio instead of the 1300's .86. This was fitted with the larger engine, freshly overhauled by Bob Dove and should be no trouble. I do not know what speedometer drive is fitted however. The axle is the original as far as I know and is probably 4.55:1 giving you gearing that is standard for a 1600cc car. The intermediate ratios are the same for all boxes, so you have 1750 spec except for the axle which should be 4.1:1 as standard.
I have a bit of a clunk coming from the diff when the car is moving at slow speed, so will look into this at some point, maybe at the same time upgrading to the 1750 spec.
Not sure, I get mine just as the backlash is taken up.
A high revs clunk sounds more like a cenre prop shaft bearing or perhaps the donut. When you get chance have a look underneath and see if you can see any tell tale marks where the prop shaft has contacted parts of the tunnel, you might see them as scratches around the prop shaft. I've had these but I have to confess dropping the clutch at 4500 revs will tend to do that!
A high revs clunk sounds more like a cenre prop shaft bearing or perhaps the donut. When you get chance have a look underneath and see if you can see any tell tale marks where the prop shaft has contacted parts of the tunnel, you might see them as scratches around the prop shaft. I've had these but I have to confess dropping the clutch at 4500 revs will tend to do that!
velocemitch said:
I've got a spare 1750 Axle in my Garage, but it's non LSD, I'd expect you want an LSD??
I thought the drive train would be as you say, it does explain why the speedo is out it will always read high with a 4.55 in it.
The clunk might be the UJ's, mind does it too, it's not unusual.
That is quite tempting Mitch, I'll sit on that one for a while. I take it you can retro fit an lsd?I thought the drive train would be as you say, it does explain why the speedo is out it will always read high with a 4.55 in it.
The clunk might be the UJ's, mind does it too, it's not unusual.
What I'd like to achieve is a longer reach in 5th. Currently 70mph feels ok, but any more than 4500 and the engine thrums which I try not to subject it to too often. Am I right in thinking that the 4.55 would achieve this - bring the speedo and rpm back down?
I'm not sure if you can retro fit an LSD, I know there is a visible difference in the casings of the LSD's, but not sure if that affects interchangability.
Did you mean a 4.1 diff would change the speedo and 'calm' the engine a bit?. If so yes it would, 4500 rpm in fifth would be good for over 90 with a standard transmission. Seventy is a comfortable cruising speed, the engines don't sound stressed at all at 3250 or there abouts. Wind noise is always dominant at those speeds anyway and there isn't much you can do about that I'm afraid.
Did you mean a 4.1 diff would change the speedo and 'calm' the engine a bit?. If so yes it would, 4500 rpm in fifth would be good for over 90 with a standard transmission. Seventy is a comfortable cruising speed, the engines don't sound stressed at all at 3250 or there abouts. Wind noise is always dominant at those speeds anyway and there isn't much you can do about that I'm afraid.
Sorry, yes the 4:1!
That sounds about right. To overtake I sometimes go up to around 80, which I feel is overworking the engine a bit and approaching 5k on the tach! Is it an easy change Mitch? I take it the brakes would swap over ok.
I'm going to a Red Letter driving day at Rockingham on Sunday - skid control and power drifting instruction. I'm driving the backroads over there from Derby in the Alfa - really looking forward to a good cross country drive. Don't worry, I'll be skidding Rockingham's BMW!
That sounds about right. To overtake I sometimes go up to around 80, which I feel is overworking the engine a bit and approaching 5k on the tach! Is it an easy change Mitch? I take it the brakes would swap over ok.
I'm going to a Red Letter driving day at Rockingham on Sunday - skid control and power drifting instruction. I'm driving the backroads over there from Derby in the Alfa - really looking forward to a good cross country drive. Don't worry, I'll be skidding Rockingham's BMW!
Edited by joesnow on Thursday 24th November 13:16
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