Tranny ratios

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Ron Hoff
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Tranny ratios

#1 Post by Ron Hoff »

I know this has been discussed before, but my search did not really answer my question. I have BBBD gears in my S-90 T-6 coupe. Is this the typical gearing seen in the S-90? Now that the transmission is torn down on the bench I have the opportunity to change if I wanted different gears. I plan to do typical "spirited" cruising on the backroads of the Pacific NW but freeway speeds in Oregon are limited to 65 legal, 70 in Washington. 80 mph will get you a ticket fairly quickly in most areas. I have not driven this car enough to get a good feel for its sweet spot, so looking for any advice.
Ron Hoff
NW Oregon

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Ernesto Cabrera
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#2 Post by Ernesto Cabrera »

Ron, BBAA is really Sweet for spirited driving if you are comfortable with approx. 4300 RPM @ 70MPH in 4th on the none twistys. The next best thing is a B 4th gear as on the speedster. Provided you have the 7:31 ring and pinion which is the most common ratio.
 

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Al Zim
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transmission gearing

#3 Post by Al Zim »

The faster you spin the engine the quicker it wears out. When you are driving 80 MPhH, I think this is the top of the useable limit of the 356.! I would suggest using the 4C gear to keep the RPM's low. If you really want the drivability of the 356 with power, I suggest pre 1974 911. A car with and E or S motor or converted to a 3.0 SC engine should be more that the average person can handle. Just one man's opinion al zim
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Jim Nelson
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#4 Post by Jim Nelson »

My two cents--4300 rpm @ 70 mph would make me crazy, and I've never been accused of poking along. BBBD works well in my S90 T6, and the sweet spot of 3500-4000 rpm for freeway cruising in SoCal ( the roughly 70-80 mph range) gives me a reserve for faster stretches, if you have the inclination and the opportunity to do so.

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Ernesto Cabrera
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#5 Post by Ernesto Cabrera »

Hey Guys, I'm referring to the fun quotient. The Super 90 engine, more than any of the pushrod engines is a bit nervous and likes to be pressed hard. I know a bunch of us have gotten old and set in our ways................. Give the young guys a chance to experience 356 driving at its best.
 

Dick Weiss
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S90 longivity?

#6 Post by Dick Weiss »

Back in 1986, co-drove a '62 S90 cp to the WCH in Newport Beach, CA and I cruised at 100MPH for 2-hrs. in Utah's open roads and my foot got tired; the manual cruise control (hand throttle) wouldn't come out far enough. We won the long distance award of 2415 miles and mae good friends w/the shortest driven distance of .8 miles.
After the trip west, we headed north to Jackson Hole, WY via Yosemite and Grand Tetons in the snow to Laramie, WY and had no problems other than running out of towels to wipe the fog from the windshield.
Overall, no problems encountered w/the 5500 miles driven during the 1-1/2 week trip and the S90 loved it--still does as its never been torn down since then and has participated in several holidays.

Dick

Dick Weiss
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#7 Post by Dick Weiss »

Forgot to mention--the round trip was from Cincinnati, OH and the holiday was just
2-weeks after the ECH in Louisville, KY.

BTW, the car was driven to the WCH in 1982 previously--whose car? Tom Oerther's.

Dick

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Ernesto Cabrera
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#8 Post by Ernesto Cabrera »

Back in 1969, during a college break, I took a stock 64 SC to Mexico from Altanta all the way down to Tiapas Mexico by way of Mexico City and Acapulco. In Mexico we were traveling mostly in the three digits. The only thing that past us during the trip was a 911S lightweight with German Plates.............. but I gave him a run for his money. Anyway, I was wishing I had shorter gears. The BBBC gearing was just too tall for twistys and elevation changes.
 

Ron Hoff
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#9 Post by Ron Hoff »

Thanks everyone for the advice both on and off line. I'm thinking, along with several others, I may be best off leaving well enough alone as to any change in gearing. We will be doing a fair bit of freeway travel up and down I-5 and I think keeping the revs down somewhat might be a good thing afterall. I am using stock tires, well, stock as much as 165 Kuhmos are. A variation in future tire size may be all that is needed later as I get used to the car.
Ron Hoff
NW Oregon

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Chris Duerr
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Gear ratios

#10 Post by Chris Duerr »

If your engine cannot maintain 5k revs on a sustained basis, then it wasn't assembled properly or you need to go get a stronger prescription for Midol. 356 cars are not Bugattis or other pre war stuff that are tender and breaks under duress. These cars can be driven hard for long periods of time and they actually work better in those conditions as compared to some Lady poking around in traffic. Ernie is absolutely right when he suggests BBAB with a 731 ring and pinion but most cars sit in the garage so who cares what the ratios are so long as the date stamps on the wheels all match!!!!! That is the stuff dreams are made of.

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Jim Nelson
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#11 Post by Jim Nelson »

If your engine is turning 5k revs on a sustained basis with Ernesto's gearing, you're only going 80-85 mph, and that's not the stuff my dreams are made of.

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