Old questions asked again - trans gearing and others

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Re: Old questions asked again - trans gearing and others

Postby Larry Jowdy » Mon Oct 08, 2018 1:21 pm

Mike, call Kevin at KCR trans. in Riverside. Tell him you know me and I suggested you call for a quote. He has built several transaxles for members of Spyderclub He does all my trans work and does a "GREAT" job. (1-951-688-1904)
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Re: Old questions asked again - trans gearing and others

Postby DannyP » Mon Oct 08, 2018 1:42 pm

Mike, I run stock 1-4, and a 3.44 final. If I was to change it, I'd get a slightly shorter 3-4.

If I had a 3.88, I'd get a taller 1-2 and use stock 3-4.

I have the numbers all worked out on a couple of online calculators. Changing 3-4 is cheaper than 1-2, due to the fact that 3-4 are just gears while 1-2 is a shaft and 2 idler gears(more $$$$$)

I can detail the actual numbers if you want to end up with a very usable close ratio 4 speed. It's not for drag race starts or ultmate high speed, but for blasting through mountain hills and curves, it will be perfect. Planning to build a new/extra box this winter.
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Re: Old questions asked again - trans gearing and others

Postby SpyderMike » Mon Oct 08, 2018 10:46 pm

Larryl Thanks for the referral. I will call him.

Danny, please detail your actual numbers. I would like to pull the trigger on the right trans the first time, if at all possible.

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Re: Old questions asked again - trans gearing and others

Postby EEricson » Tue Oct 09, 2018 4:34 am

Mine's the same as or similar to Danny's. I have one in Bridget, my Suby powered MG TD (1800 pounds, 137 hp) and one in the Spyder under construction (1500 pounds, 120 hp):

3.80
2.06
1.26
.93
R&P: 3.44

Some guys run the .89 4th gear and get a little lower RPMs in top gear in exchange for a slightly wider 3-4 shift.

These ratios will give you nice, even rpm drops between shifts and, depending on how high-strung your engine is and how tall your tires are, can yield speeds very much like the originals. This is what I'm shooting for and, given my engine should peak at 5500 and rev not too far past 6000, here's how I calculated for a car set to run 165/80-15s:

Original Spyder-------------vs------------Replica
Top speed in
1st: 40 mph-------------------------------35
2nd 66-------------------------------------65
3rd 105------------------------------------105
4th 137 @7400---------------------------143 @6000
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Re: Old questions asked again - trans gearing and others

Postby SpyderMike » Tue Oct 09, 2018 8:14 am

Thanks for chiming in! Who did your trans if you don't mind me asking?
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Re: Old questions asked again - trans gearing and others

Postby RBP » Tue Oct 09, 2018 9:36 am

I've ran a 3:88 R/P with a 3.10 1st, 1.93 2nd, 1.26 3rd, and a .82 4th. Works perfect but personally, I wanted a taller 4th, revs to high just trying to keep up with traffic on the expressway. A 5th would have been ideal. I now run a quaffi with a 3:44 R/P, a 3.80 1st, 2.06 2nd, 1.26 3rd and a .89 4th. I get maybe 3 mph more on the top end and a great relationship between all the gears. There isn't much difference between the 2 configurations but there is a tiny bit more top end in 4th (I took anything I could get).

The difference is in the cost, much less $ to go the 3:44 route and stick with the basic gears than to go the 3:88 route and the more custom and costly gearing!
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Re: Old questions asked again - trans gearing and others

Postby egrant5329 » Tue Oct 09, 2018 12:32 pm

Kevin at KCR did my transaxle. I think it was the pro-street or pro-street plus. It's a 3.44 with 3.78 1st, 2.06 2nd, 1.26 3rd and a 0.93 4th. No quaiffe and it has the aluminum side cover on one side. I like the step from 3rd to 4th, but it would be nice to have a taller 1st gear.
I would suggest looking at one of the RPM/speed calculators with what ever tire size you plan to run. Look at what speed you typically cruise the highway and pay attention to what RPM you will be at. I really like being ~3000 rpm at 70mph and 3250 at 75mph. That's the speed traffic seems to run and you have a lot of top end remaining if you feel like risking you life more.
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Re: Old questions asked again - trans gearing and others

Postby EEricson » Tue Oct 09, 2018 5:37 pm

Mike, both my transmissions were put together by Jimmy Sartwell. He's local to me and does a lot of drag boxes, working out of whatever garage or shop will let him basically live there.
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Re: Old questions asked again - trans gearing and others

Postby SpyderMike » Tue Oct 09, 2018 6:30 pm

Thanks for the input RBP, Egrant and EEricson...looks like I have some calculating to do.

This car was replaced in the driving hierarchy by other cars and some motorcycles over the 30 years I have owned it. It ended up at the bottom of the drive list some time ago (maybe 20 years or so). I haven't driven it in so long that I can't remember the last time. I am committed to getting it back up higher on the list. I recall the trans gearing and a strap mount being the main issues back then. There seems to be quite a few different ways to go.

I also will be doing a better carb linkage setup - maybe the hex bar mod or the center swivel setup. But, the trans is the biggest focus for me right now based on the effort and cost.

I really appreciate the responses.

Mike
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Re: Old questions asked again - trans gearing and others

Postby RBP » Wed Oct 10, 2018 5:23 am

Ed, what are you running for rear tires. I'm on 205/55/16 and run at about 70 MPH at 3000 RPM with the .89 4th. I figure I'd drop about 5 MPH with a .93 4th unless I found rear tires of larger diameter.
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Re: Old questions asked again - trans gearing and others

Postby egrant5329 » Wed Oct 10, 2018 5:34 am

I moved to these last year, Coker Vredestein Sprint Classic, 185/70HR15 (25.2" diameter). I still have my 185/65/15 and 195/60/15 on my steel wheels If for some reason I needed something wider.
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Re: Old questions asked again - trans gearing and others

Postby DannyP » Mon Oct 15, 2018 1:48 am

I'm running 3.80, 2.06, 1.26, and 0.89 with my 3.44.

I'd like to change 3 and 4 to 1.39 and 1.04. Not drastic change but a very even percentage between gears. 70 mph becomes 3400 in 4th instead of 3000. I drive mostly 55 roads and twisty stuff. Most often I'm in 3rd gear, and 4th is too tall. My current second is revving out and 3rd is a bit too tall. I think the shorter 3-4 would make the car more fun in the mountains. Really the current 4th should become a cruising 5th but not practical in a swing-axle Spyder.

Top speed drops from a supposed 143 to 123 at 6000rpm. Honestly, we'll never see either of those. At 110, the front end starts to get very light. I hit 125 indicated once a long time ago, and it was really around 115 given the optimistic VDO speedometer.

I used Weddle's calculator for this, my percentage pull(or spacing between gears) becomes: 1-2 31.8%, 2-3 33.5%, and 3-4 at 34.7%. Really even, and the lowest cost way to do it.

The real money is in the LSD. They go for 1500 minimum for a ZF LSD to over 2K for a Torsen type.
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Re: Old questions asked again - trans gearing and others

Postby EEricson » Mon Oct 15, 2018 4:44 am

My tires? Tall skinnies on the MG: 165/80s on 15-inch wire wheels.

Planning to run the same in Vredstein Sport Classics on the Spyder, but not 100% on it yet.
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Re: Old questions asked again - trans gearing and others

Postby sjgharib » Mon Nov 12, 2018 9:27 am

Perhaps this may be useful to folks

When I was trying to choose gears, I figured one place to start was to understand the original transmission that was mated to my engine by the factory (I have a Subaru, so it was originally in a car with a Subaru 5 speed transmission), then compare it to the choices I had on the VW transaxle.

Also factoring in the size of the wheel / tire combination to calculate RPM vs vehicle speed in all ratios.

The math is correct - I have very accurate correlation between my calculations and actuals (I data logged with MegaSquirt, which allowed me to collect RPM & GPS based speed, and by counting the shifts I could pretty clearly deduce what gear I was in).

The nice thing is you can just drop in gear ratios, final drive ratio, and tire specs (i.e. 205/55R16) and it drops out the graphs.

Happy motoring!
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