Can anyone tell me what the exact final ratio is..

[regularman]

for 5th gear in the FS5W60A Datsun transmission that is used in the conversion is?

 

[Baz]

Try this, it has an F in it....
https://www.mgcars.org.uk/midgetspriteclub/sprite/sprite5speed.htm

 

[regularman]

Thanks Baz, looks like it is .846 in 5th. Just trying to figure out my rpms at 60 or 70. I got 175/70/13 tires on my midget. I can't remember what size stock was. Maybe 145/80/13?

 

[Trevor Jessie]

I thought it was .82 in 5th. I guess I was being optimistic.

My rpms at 60 are almost exactly 3000 with 3.9 rearend and 165/70.

 

[regularman]

I may not use 5th much then. I changed my rear gear to a 3.55.

 

[Trevor Jessie]

2576 Rev/min at 60mph with a 175/70 and 3.55 and .846 overdrive.

 

[regularman]

Man, that is going to be weak, but might be ok on flat ground for giving good mpg and that was my intent. I intend to go places in this car and hated the engine whine on the highway.

 

[Trevor Jessie]

Before adding the supercharger I had to drop down to fourth if I want to accelerate or pull a loooong steep hill. However, your acceleration from still should still be good since the datsun first and second are lower than stock. It might give you motivation to add a supercharger or turbocharger in the future. (I can now accelerate in 5th gear from 65 to 90 with no problems)

 

[drooartz]

Trevor -- what rear end were you running before you went to the supercharger?

 

[Trevor Jessie]

Same 3.9.

The 3.9 and five speed and 1275 was fine... rarely did I have to drop out of 5th gear to maintain 65 mph.

 

[drooartz]

Thanks Trevor. I'm starting my calculations for the 1275 upgrade to the Tunebug, and I've been wondering if I'll keep the 4.22 (I've got a 3.9 handy as well). I've got lots of long, steep grades, plus mountain passes up to 8000 feet or so. Not really Sprite territory. /bcforum/images/%%GRAEMLIN_URL%%/grin.gif

 

[Trevor Jessie]

I'd think the 3.9 would be fine. The bugeye is light, and fourth gear is good up to about 88 mph with most stock 1275 engines. How fast do you want to go up the mountain?

 

[kcbugeye1275]

Any carberated auto is going to have power problems at a change of altitude if it doesn't have a supercharger or a turbocharger. One of the things that induced me to go with the supercharger was a story of a smiling old man who pulled into the Denver all Brit in an old bugeye many years ago. The friend who told me the story said he had an Judson supercharger on his bugeye and had been passing some big Healys in the mountains.

 

[drooartz]

Right now, with the tired 948, I can manage about 35 tops on the main freeway grade from my house to work (about 1000 or so elevation gain over a couple miles). I'd be pretty happy with 50, really.

I've been thinking some about supercharging, given the altitude (5550' up to about 8000' or so around here), but the cost is pretty steep. Once all those costs are factored in to my budget, I start looking at just buying a car with a much bigger motor.

 

[regularman]

Re: Can anyone tell me what the exact final ratio

Before adding the supercharger I had to drop down to fourth if I want to accelerate or pull a loooong steep hill. However, your acceleration from still should still be good since the datsun first and second are lower than stock. It might give you motivation to add a supercharger or turbocharger in the future. (I can now accelerate in 5th gear from 65 to 90 with no problems)

Here in the mountains I plan on having to gear down on the hills. I will just have to see how it works out. Worst comes to worst, I can find another 3.90 hogshead and swap it out. I don't think I would fool with changing the gears back. It takes time.

 

[regularman]

Re: Can anyone tell me what the exact final ratio

I sent an email and asked rivergate what the final gear ratio was in 5th and here is what they said <div class="ubbcode-block"><div class="ubbcode-header">Quote:] [/QUOTE]

Will Perry
Rivergate The overdrive ratio is .86.

From: Kim A Webb
Date: 2007/03/22 Thu AM 01:40:11 EDT
To: rivergate5speed@bellsouth.net
Subject: 5 speed gear ratio question.

If I did one of these conversions, what would the gear ratio be of the
the FS5W60A transmission when it is in 5th gear . What is the exact
overdrive ratio? Thanks