pewter82

The car is stock and its a 5speed 83 US, It feels very strong now, where will I feel the difference with the new ratio?

Jason

83S 5Speed

MarkRobinson

Huge difference. YOu'll be shifting a LOT, kinda like driving a Honda, but with wheelspin.

GlenL

(Lemme get in here before Kibort wakes up.)

Yes, but only really off the line from a standing start.

Once you're into second and third the total ratios overlap and it's a wash. That is, with the new final drive there are speeds where, for example, you'll need to be in third already where with the 2.2 you'd still be in second.

MarkRobinson

True! I raced a friend in his 928 years ago:
His car: '82 US 928 with Euro CIS engine, Ansa exhaust: 273/275rw, lighter than my 86.5 car, but without spoilers. Stock 2.73 rear end.

My car, '86.5 US 32v with stock 2.20. Both cars were 5-speeds. From 20-60, he pulled about 5 cars on me! @80, he was no longer pulling, @ 120, I was next to him, @ 140, I had a car length on him. Intersting: gears, he killed me to about 60-70, but aerodynamics took effect, helped even the odds. My car was lowered about 3", his was about 1".

M.

jyoon

it will make very little difference except in 5th gear. Check our Kibort ratios/speeds in gears on flyingdog's signature. 1st gear 83 US is 46.10 MPH@6000 RPM and 1st gear 83+ Euro is 43.46 MPH@6000 RPM. 2nd-4th are also pretty close. the only difference will be 5th where you will notice a fair amount of difference.

heinrich

It makes a HUGE difference in the feel of the car.

jyoon

there will be a huge difference if you take an otherwise stock 2.20 rear tranny and put in a 2.73 rear. however, i still don't see how there can be much difference other than in 5th on stock trannys assuming kiborts numbers are correct.

Jim bailey - 928 International

the final drive ratios for a USA 2.20 with USA layshaft ratio 1.5714 are first gear 8.947, 2nd 5.9712,3rd 4.254,4th 3.218,5th is of course 2.20 . The Euro box (similar to early USA) with the 2.7272 final drive and Euro layshaft ratio (1.4545) gives you a 1st at 10.239,2nd at 6.838,3rd at 4.881.,4th at 3,68 and 5th is 2.7272 ....5th is always direct drive power straight in the input shaft to the pinion. What you get with the Euro or early USA is a much lower first gear PLUS a 5th gear which is only 34 % taller than 4th where the USA 2.20 has a 46% taller 5th. Open road racers and WALT K have spoken of "hitting the wall" when shifting from 4th to 5 th with the USA gears at full throttle top speed and the car barely is able to pull in 5 th. Basically the EURO box is a close-ratio 5 speed and the USA is a 4 speed with overdrive. The more gears you have and can use between 0-150 MPH the closer to maximum horsepower rpms you run the engine the faster you will accelerate. Less a bit for lost time shifting

mark kibort

Only ini 1st, as glen says. (thanks Glen!)

the rest wont actually feel any different, unless you look at the stick shift and notice what gear you are in . speed to speed comparison, will have trade offs after the intersection of where the new first gear shifts into the new 2nd gear. then, let the trade offs begin.

as i aways say, acceleration is porportion to HP. the lower "new" first gear will allow more hp to the wheels (if you can keep the wheels from spinning) out of the shoot. however, after that, its a series of trade offs.
acceleration = power/(mass x velocity)

so, a 2.75 is a pretty dramtic bolt on to a stock 2.2 transmission. quite a bit more than the normal 10-12% differences of a real 2.72/2.75 and a 2.2, as just that bolted on will give you a 25% /.8 difference! If you look at the new ratios, you can plot out where your advantages (and disadantages) will be.
overall gain in acceleration barring wheel spin will be out of the hole, to 44mph. after that, there will be no "feel" differences. However you may perceive a difference , as you are shifting more, not accelerating any faster through the gears after 44mph. (stock 2.2 1st gear goes to near 55mph)

remember the drill we did with the 3.09? that was such a dramatic change, that all the gears just shifted down one entire gear space. so, we got a "sub" first at 12:1 or something, then the rest of the gears just added up to equaling the prior gear box. funny, that some that drove the car, said how fast it was, but besides to 39mph, there would be NO difference in acceleration beyond that speed. a 2.75 bolted on a 2.2 would approach this change of the 3.09, but end up somewhere in between.

Mk

heinrich

NO.

I am not saying there might be a theoretical difference if this or that, and the numbers support this or that. i am saying this:

I have driven both boxes in comparison, both on long trips and short trips next to each other, and swapped drivers intermittently. And the end "feel" of the difference is MASSIVE

6.0-928S

I second your motion. Heinrich knows of what he speaks!!
Hammer

mark kibort

Since we have gone over the gear advantages, you can see, the effects will only be in the 1st gear, and then with trade offs after that. try and race your friend from 50 to 80 !! or better yet, 95 to 115. you will kill him.
no better proof of this is with scot and his new race car. (2.72 stock 82 trans)
he has 260rwhp and i have near 320. I was much heavier with all my tires and stuff in the car and we did my 60-100 test. out of the gate, he pulls me by a half of a car length. at 80 he has to shift, and not only do i have a hp advanage, but a gear advantage as well. over all, i beat him to 100mph in the end, probably as i would beat him if he had the same gears.

again, gears dont buy you HP, they buy you specific advantages of applying HP over any certain vehicle speed ranges in the form of trade offs
Even in the extreme case of the 3.09:1 bolt on, there is even a trade off in 1st, in the form of a trade off at the high end in 5th ( ha ha, 3.09 doesnt have a 5th now,but is a monster from 0-39mph if it can apply traction) But besides that, there is really no differences after that "sub" 1st through the speed range to 145mph.

with a differece in aero of .32 vs .36 drag coef. or something, thats not going to play a part in your comparisons, especially at the speeds you are talking about. what will make a difference, is the weight you and your friend are at. when im loaded to the track, my 60-100mph goes from near 6 seconds to near 6.6seconds. ( near +500lbs.)

Mk

jadavis01

I thought the 83 US 5sp had a 2.36 rear end.

svp928

Having done this swap, I can say the close-ratio box and 2.73 rear end DO make a HUGE difference in how the car feels, especially from a dead stop, or slow roll in first. Mark is right, after the first or second, you shouldn't notice that much difference, but having the ratios closer together keeps the car in the powerband at every shift, and this is noticeable. Grin!
If you are just changing the final drive, your results may vary...but 1st will definitely feel a lot stronger, and all the gears will feel closer together. IMHO, it increases the car's fun factor signifigantly in everyday driving.

heinrich

Remember, the question here is not about horsepower. Not about torque. not about science. The question (read it above, first post) is .... does it feel any different? Answer: YES. TOTALLY.