1968 3500 Auto to LT77

MackyD

New Member
Hi, I have bought a 3500 auto that has been converted to 5 speed. However, the install is a bit of a "dogs dinner" and the heat shield for the brake master cylinder is resting on the exhaust manifold to fit an unknown clutch master cylinder next to it.If I am unable to source 3500S parts or left hand drive parts. Is there a reliable alternative?
 
The brake master is probably OK like that, but there ought to be a better way to protect the clutch master. An extension of the brake shield upwards and forward? Down here copper pipes are forbidden for modifications - they work harden, become brittle and crack. CuNiFer (copper-nickel-iron alloy) is the best option.
 
Looks like a fun way to do it. Saying that, if it works ok, I would be inclined just to make up a new brake shield as JP says, and paint it silver.
 
Hi all, the problem is that the clutch fluid is cooking and starts to fade quickly. When I depress the clutch and engage gear the car starts to move even before I start to take my foot off the clutch. Once on the move it seems ok. The system has been bled several times but the fluid comes out black in colour. Grrrr!
 
Hi all, the problem is that the clutch fluid is cooking and starts to fade quickly. When I depress the clutch and engage gear the car starts to move even before I start to take my foot off the clutch. Once on the move it seems ok. The system has been bled several times but the fluid comes out black in colour. Grrrr!

When I stripped my car down for a rebuild, I took a few pictures of the clutch master cylinder and how it was fitted, as it used to be an auto, and someone else had installed the 5 speed gearbox.

Sparky's winter/spring/summer/autumn work

And this is during the rebuild.

1668366237793.png

Is that any help?
 
Is there a speedo drive on the LT77? One converted car (1975) I was looking at had a separate speedo added to the left of the binnacle.
 
Just in case it may be useful to others doing an LT77:
Speedo drive gear (mechanical drive , alloy housing on left rear) - many different gears around for different installation, colour coded. I was led to believe a red gear was correct for a P6 with 3.08 diff. On the road it showed 40 when doing 60 +/- 2-3. Pulled the drive out just now (not fun!) , red, 22 teeth. Have an orange - 20 teeth - trying that next outing. The confusing part is the drive gear on the gearbox output shaft comes in at least 2 forms - black, 8 leads (NOT teeth or threads), and white - 7 leads. Dont know whats in my box, havent been able to find any info on these, except that Rimmers stock the black and white gears:- TKC1273 and TKC1274, cheap too. Still want to find out which of these gears were fitted to SD1 LT77 boxes - 3.08 diff, 195-70R14 tyres - very close to P6B.
This web page is useful :-
Morgan Plus 8 speedo Gears
 
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Rover 5 speed speedo drives (LT77 etc)


Speedo transducer; 1982 onwards (electronic speedo). 2 pin connector

3500 (20 teeth, orange) 3.08:1 axle ratio.

2600/2300 (23 teeth, black) 3.45:1 axle ratio.

2000/2400TD (22 teeth, red) 3.09:1 axle ratio.


Speedo drive gear; 1976 - 1982. Models with mechanical speedo.

3500 (20 teeth, orange) 3.08:1 axle ratio.

2600/2300 (23 teeth, black) 3.45:1 axle ratio.

? (24 teeth, blue) axle ratio ?

? (21 teeth, green) axle ratio ?

? , (25 teeth, white) axle ratio ?
 
If 22 teeth red gear gave me 40kph at GPS 60kph, going to an orange 20 teeth gear will only give me an indicated 44kph at true 60. Where do I go from here - recalibration?
 
put the 20 tooth one in and try it. From memory they are a skew gears (a multi start worm and wheel) and counting the teeth doesn't work for ratio measurements.
 
I think it's Dakota instruments that do an electronic to mechanical conversion for speedos. It uses an external stepper motor to drive your standard speedo. They have a Melbourne (or nearby) supplier.
Finally, The speedo gearing is written on the very bottom of the face, below where the bezel sits. You might want to check you have the right one...I don't have one handy so I can't give you the correct number but maybe someone else on here does?
 
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More info. The std P6B speedo for MPH is 1248 turns (of cable) per mile, a KPH speedo is 780 turns/km.
Based on std tyre dimensions of 185-70R14 these should do 518 revs/km, which is 1597 revs of the prop shaft. At those revs of the engine in top gear the speed is 60 kph. If the speedo takes 780rev/km, then the gearbox reduction is 1597/780 = 2.04, so reduction is most likely 2:1.
With my car and its LT77, with the 22 tooth red speedo gear, I wanted to know what the output shaft driving gear was - 7 or 8 lead. My tyres are 195-75R14, 5% bigger than std, which should do 491 rev/km=1513 revs of the propshaft. Reducing these turns by 8/22 speedo gears gives 550revs. 550/780 gives .705, which means at 60kph an indicated speed of 42.3, very close to what I saw on the road. So I think the speedo driving gear is a black 8 lead type. Now that I have a red 20 tooth speedo driven gear fitted I should see 46.5 indicated at a true 60kph. Road test time.......
 
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