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Discussion Starter #1 (Edited)
Seems like a lot of cooling fan noise at 5000 RPM vs. my '87. How can I tell if I have the correct fan?

Seems to be revving fairly hard at 70. What RPM at 70 mph with a stock differential? How do I determine if my differential is stock?

Thanks
 

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I think the earlier cars had 4.56:1 axle ratios, the later cars have 4.1:1 ratios. There may be an external clue on the differential but one way to tell is to jack up the rear end, put the transmission in neutral and count how many turns of the driveshaft makes the tire turn one revolution. (4 1/2 turns vs slightly more than 4 turns)
 

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There are two fan styles, a thinner Euro and a USA fan. Both are acceptable. Does your 87 have a clutch? 74's didn't have a clutch.
Is your fan missing any chunks out of the blade arms? Is your water pump going and noisy?
You can jack up your car and count rotations. Do a search on this website.
 

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My 1976 revved a LOT higher at Hwy speeds than my 1983. Not sure what year they moved away from the 4.56's but yours definitely came with the deeper gears from the factory, and it sounds like it still has them!
 

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Yep, should have 4.56, 10% shorter than a Bosch Spider, so 10% more rpm at a given speed. What tire size? That affects the gearing too.

Both should have had mechanical fan on pump, not clutch. There are three or four different fan designs, the bigger the blades the more noise.

Looked like Carlsbad from the pic; I lived there 74-81.

Andrew
 

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ya its just a different form of performance. i own both a 70s and 90s spider. and one is great for highways, but pretty sluggish off the line, while the other (which yes, barely gets to 90mph) can lay rubber down, and haul *** off the line. also the 70s model can climb hills and accelerate out of turns like a bat out of hell.

i like them both in their own ways.
 

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Discussion Starter #8
ya its just a different form of performance. i own both a 70s and 90s spider. and one is great for highways, but pretty sluggish off the line, while the other (which yes, barely gets to 90mph) can lay rubber down, and haul *** off the line. also the 70s model can climb hills and accelerate out of turns like a bat out of hell.

i like them both in their own ways.[/QUOTE

You nailed it. That's why I told my wife I needed 2 Spiders.
 
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