Question - final drive ratio

Discussion in 'Workshop Forum' started by jovani, Apr 16, 2018.

  1. jovani

    jovani True Classic

    Location:
    scottsdale
    Wonder if anyone knows a way to increase final drive ratio on 5speed gearbox? I am perfectly happy with the gear ratios, but all 5 gears are way too low. My car cruises 70 mph with just slightest throttle touch, has plenty of power, to say, to have 6th gear. I would like to run at this speed at much lower RPM and I don't know if different crown/pinion ratio is available, like on earlier Renault transmissions.
     
  2. fiatfactory

    fiatfactory Steve Cecchele

    Location:
    Western Australia
    search the forums, lots of info out here. Common upgrade is the final drive from a US spec Strada at around 3.76:1.

    SteveC
     
    myronx19 and Dr.Jeff like this.
  3. Dr.Jeff

    Dr.Jeff True Classic

    Location:
    Sin City
    Although it might not be practical in your application, but one easy way to change the final drive ratio is with tire circumference.
     
  4. Jeff Stich

    Jeff Stich True Classic

    Location:
    Norco, CA
    The US-spec Strada 5-speed final drive ratio is 3.59:1.
     
    myronx19 likes this.
  5. The above mentioned Strada ring and pinion is a pretty easy swap. I have done several. However, the really hard part is finding one.
     
  6. Rupunzell

    Rupunzell Bernice Loui

    Location:
    California
    Not a good idea. Chassis-suspension behavior will be impacted and not in a good way.
    The overall window of diameter of tire and wheel that works well on the exxe is small.

    Bernice


     
  7. Rodger

    Rodger True Classic

    Location:
    Olympia, WA
    I just did the Strada ring and pinion swap on mine and am very happy with the results. I had picked one up off of ebay almost 10 years ago and finally got around to giving it a try. It drops the RPMs about 500 when cruising at 65-70. I have a MWB performance head/cam upgrade so the car still has good acceleration. Not quite as quick as with the standard final drive, but it makes highway driving more relaxing. Guess I am getting old. :(

    You might try posting in the FS&W forum, to see if anyone has a Strada final drive stashed away.
     
  8. Dr.Jeff

    Dr.Jeff True Classic

    Location:
    Sin City
    Rodger, your feedback is valuable. Interesting, somehow I would have guessed the RPM drop might have been more; maybe 1000-1500 rather than 500, but just an assumption without doing the math (truthfully I've not looked into it before). Along that same thought, I would have guessed that if the RPM only decreased 500 at 65-70, then the decrease in acceleration ("not quite as quick") would not be very noticeable. Again just assumption. But overall, you would say the effects are better than the stock ratio for regular driving? Thanks again for your input, I'm trying to get a feel for the differences it makes.
     
  9. Rodger

    Rodger True Classic

    Location:
    Olympia, WA
    As I recall, the RPMs at 70mph were around 4000 with the stock final ratio. When I was younger, it never seemed to bother me, but with age and driving a lot of 6 speed manuals, the X at 4000 rpm seems kind of frenetic and begs for a 6th gear. With the Strada drive, the RPMs are around 3500 which doesn’t sound like a lot, but I find it more relaxing.

    If my ‘79 was still stock, I would not recommend it because of the lower horsepower, but with fuel injection and the performance head, it is a good combination.
     
    Dr.Jeff likes this.
  10. fiatfactory

    fiatfactory Steve Cecchele

    Location:
    Western Australia
    4.077 to 3.59 is a 12% drop, so at 4k revs will drop 480 revs to 3520 (4000 x 0.88)

    It will also drop rear wheel torque by 12% too, as gear ratios are torque multipliers... so unless you also improve engine torque by about the same amount, acceleration will suffer.

    SteveC
     
    Dr.Jeff likes this.
  11. Ulix

    Ulix True Classic

    Location:
    Stuttgart, Germany
    I ran a built 1600 with a 4-speed (4.08) and installed a 3.67 ratio.
    It made things better on the highway, but the car also lost a bunch of its attitude.
    Also the jump from 3 to 4 got huge, but this won't be as much of an issue as 4th is shorter on the 5speed.

    I am now just finishing a 1.9L build and am deliberately sticking with stock ratios in the 5speed, even though I live in a (the) country without speed limit.
    For me the sportiness of the car is more important than cruising comfort though.
     
    Dr.Jeff likes this.
  12. myronx19

    myronx19 True Classic

    Location:
    Toronto, ON Canada
    I had a 3.59:1 in my race car, and it wasn't great at Mosport going up the straight. I replaced it with the stock diff and it was much better for that engine.

    However, I will use a 3.59 in my stock '82 gearbox with my Uno Turbo motor. I found a Strada transmission in the US and will use the final drive from that box with my Turbo. Should help.

    My Abarth 500 is a 5spd, and I don't mind that it's not a 6spd. :) It seems to be geared quite nicely, and it really pulls no matter what gear you're in!
     
    Dr.Jeff likes this.
  13. Dr.Jeff

    Dr.Jeff True Classic

    Location:
    Sin City
    I guess this is what I found interesting. Naturally I would expect a decrease in torque (acceleration) as the trade-off for decreased rev's. But with this relatively small amount of final drive ratio change (<500 RPM), and only a 12% torque loss, I would not have expected it to be very noticeable. 12% doesn't seem like a lot. But I guess when there isn't much torque to begin with, then 12% is significant...as many have reported with their experiences.

    So it seems the <500 RPM drop at freeway speeds may not be worth the trade-off in torque loss, naturally that depends on how much freeway driving you do with the X. Personally I view it as a play car, for occasional around town or bar hopping/car show type use. So very little freeway use. That would be different if the following were true:
    Now you're just rubbing it in, Ulix. :)

    With the old school front wheel drive VW's it is common to swap the 5th gear set with a taller ratio. On those trans the 5th gear is sort of independent of the other 4 and therefore can be changed without effecting the rest of the gears. In fact it can be done without opening up the whole box (5th is in a separate compartment, it was a after thought). This gives the best of both worlds; retains good acceleration through the gears, until you drop it into 5th on the freeway and the rev's drop. That would be nice if it could be done on the X's box. :(
     
  14. jovani

    jovani True Classic

    Location:
    scottsdale
    Thanks !
     
  15. jovani

    jovani True Classic

    Location:
    scottsdale
    Thanks for replies! Will look for Strada tranny parts, 500RPM drop will be perfect. I use my X to go to work, frequently driving 15 miles highway one way, so even Honda Fit engine/manual tranny swap is a thought - tight package, correct exhaust side, close OD tires to the X, alu cast, no grater stress on the X rear structure, could use the AC, great engineering etc.
     
    myronx19 likes this.
  16. Daniel Forest

    Daniel Forest True Classic

    Location:
    Montreal,Canada
    I'm probably stupid, but I'm going the opposite way with a 5.88 ratio on my spare transmission. I want to see what it would do on an autoslalom car. I was told I would have to shift too often. Maybe... but don't hold up your breathe. I'm doing r-e-a-l s-l-o-o-o-o-w progress with my car. It may hit the road this summer.But don't expect the spare tranny to be tried before another year...
     
  17. Dr.Jeff

    Dr.Jeff True Classic

    Location:
    Sin City
    If nothing else it might make for a good 1/8 mile drag race car. o_O

    Actually it all depends on the race course layout, the ratios of the gears you use on that course, the tire circumference, the engine's power band, your driving technique, etc, etc...so it might work. Be interesting to see. What did the 5.88 R&P come from (aftermarket custom or something factory)?

    No comment on your initial observation posted above. :)
     
    Daniel Forest likes this.
  18. This is very true. I tried for many years to use an X1/9 as a GT and the answer is that you can't. Conversely, I had an Alfa 1750 GTV that was a great GT but the steering and general handling weren't comparable to the X1/9 (especially the speed of the steering). So I suppose that you either have a sports car, a GT or a compromise.

    Dom.
     
    Dr.Jeff likes this.
  19. Dr.Jeff

    Dr.Jeff True Classic

    Location:
    Sin City
    Dom, especially if you wanted to use the X as a "GT" ("freeway driver" to us Americans) on the Autobahn! I can only imagine what the engine is doing at 90-100 MPH (145-160 KPH) or more (assuming it will do that). :eek:
     

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