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transmission modification

Discussion in 'Workshop Forum' started by bill, Sep 15, 2010.

  1. bill

    bill my cockatoo likes you

    Location:
    minnesota
    hello i remember hearing that it was possible to use a 4 speed and a 5 speed and make a 5 speed with the 4 speed differential is this correct? never worked on the 5 speed before i know there similar but not sure if this is a "x1/9 myth"
     
  2. Mark Plaia

    Mark Plaia True Classic

    Location:
    Springfield, OR
    Myth -- using FIAT parts.....

    As far as I know.

    I have a FAZA 5-speed conversion transaxle in my car, and there are a number of special, custom parts plus specific modifications to the transaxle case. So, I do have a 5-speed transaxle that uses the 4-speed differential and axles.

    I have never heard of someone converting a 4-speed using FIAT supplied parts. I suspect that if it were possible, someone like Steve Hoelscher would have done it.

    Ciao,
     
  3. AngleT

    AngleT Always more tuning to do

    I would say "No"

    The case and gear shafts are longer in a 5 speed to allow space for the 5th gear. A 5 speed shaft will not fit in a 4 speed case. The gear shaft and the diff have to match, so if the gear ratios are different, it isn't going to fit together right and not work. If you want a different gear ratio in the final drive, custom parts will have to be made/bought. sorry.

    Different gear ratio final drives are out there if you ask around.

    Like Mark said, Steve Hoelscher is a guru with these trans and could point you to some good options.
     
  4. Niklas Andersson

    Niklas Andersson Daily Driver

    Location:
    Eskilstuna Sweden
    I guess I've done the impossible then. :cool:

    I took the inner parts and the 5-speed case-extension and mounted them together with the 4-speed final drive in my 4-speed casing.

    I needed to weld on some tabs and machine (mill and tap) so I could mount the case extension instead of the 4-speed case lid.

    I also needed to file down one of the support ribs inside the casing about 1-2 mm in order to engage the fourth gear.

    I did this so I wouldn't need to change drive shafts but still get more gears.
     
  5. Old Fiat Driver

    Old Fiat Driver Old Fiat Driver

    Location:
    Chula Vista
    another approch

    I melded together a X19 5 speed with an X19 4 speed and a yugo 5 speed. The ring gear in the X19 4 and 5 speeds are the same assuming 4:08 ring and pinion. I ended up with a 4 speed carrier and ring gear and a X19 4 speed case with some Yugo case parts. I then had Summers brothers make me axles out of 302 steel that used the 4 speed tripod inner joint and the later X19 5 speed outter CV joints. I also added lower 4th and 5th gears PBS style.I ended you with a 5 speed with the later lower 1st gear and the possitraction from the 4 speed and larger outter CV joints. You can do about anything you want but it's a little work.

    Charlie
     
  6. Mark Plaia

    Mark Plaia True Classic

    Location:
    Springfield, OR
    Cool, Charlie!.....

    I would like to trade gear charts with you to see how your approach compares with the FAZA setup that I have.

    Ciao,
     
    Last edited: Sep 16, 2010
  7. bill

    bill my cockatoo likes you

    Location:
    minnesota
    gears

    i have the stock 4 speed gears from a 74
     
  8. Mark Plaia

    Mark Plaia True Classic

    Location:
    Springfield, OR
    Here is the FAZA 5-speed gears/speeds chart.....

    [​IMG]

    This transaxle has a different 5th gear ratio and a different final drive ratio that never came in North America single cam transaxles.

    Ciao,
     
  9. AngleT

    AngleT Always more tuning to do

    So, what your saying is....

    It's a stock 5 speed trans in a 4 speed case?
     
  10. bill

    bill my cockatoo likes you

    Location:
    minnesota
    humm

    looks like 4th gear get's stepped up and 5th is added as a gear and not overdrive and the final drive ratio is raised from 4.07 or somthing like that to 4.368. do those gears fit in a 74 4 speed case? i know my 4th gear is .90 in mine i think.
     
  11. Mark Plaia

    Mark Plaia True Classic

    Location:
    Springfield, OR
    The first four gears....

    match the ratios of a 128 transaxle. The 5th gear and the final drive are from a Euro FIAT model that used a similar transaxle.

    Your 4-speed ratios will be:
    3.58/2.24/1.46/0.96 that are coupled to a final drive ratio of either 4.08:1 or 4.42:1 depending on model year and whether in California or North America smog trim.

    Interesting trivia: The X1/9 4th gear ratio is 22 to 21 teeth = 0.96
    128 4th gear ration is 21 to 22 teeth = 1.043

    Ciao,
     
  12. Ulix

    Ulix True Classic

    Location:
    Stuttgart, Germany
    Yugo parts?

    Don't Yugo 5-speeds use tripode style axles?

    Wouldn't this be the ticket?
     
  13. fiatfactory

    fiatfactory Steve Cecchele

    Location:
    Western Australia
    Not a Myth....

    done it more than a few times, and there a write up about it here...

    http://www.turbo124.com/forum/viewtopic.php?f=10&t=4244

    My Strada 65CL is basically the same gearbox too...tripode inners, four speed style differential carrier, 180mm flywheel and 4 speed starter motor... but it's got 5 forward gears from the factory.

    SteveC
     
  14. bill

    bill my cockatoo likes you

    Location:
    minnesota
    thanks

    i read your writeup on it. is the procedure the same for all 4 speed gearboxes for the x1/9? i have a 74 box in a 78 car. my rollers broke off the driveshaft when i first got the car and broke the case so i had to switch boxes. i think the flywheel is different as well but not sure about the internals or the case itself.
     
  15. fiatfactory

    fiatfactory Steve Cecchele

    Location:
    Western Australia
    74 gearbox is a little different to a 78 in a couple of ways... the input shaft has the reverse gear cut in a different place (closer to second gear) as the 1/2 synchro slider was changed (reverse gear around the top facing second gear as opposed to the early slider having the reverse gear facing first) along with the syncromesh assembly, and the 1/2 shift fork... sort of complicated to explain without pictures, but doesn't affect the conversion process, as you chnage the entire input shaft anyway...

    The trouble is that in the USA you dont get the same models that we do here in Australia, specifically the regata 85... you get the strada, but the five speed strada has inner CV's (repezza joints) not tripodes.

    The regata 85 gearboxes are five speed but with tripode inner joints, and come with either 3.58:1 or 4.08:1 final drive ratio, so it make the conversion a lot simpler as far as using a complete innards to exchange.

    You could get around it by using the 13 tooth pinion from a 4.08 five speed set, and then mating it to the 53 tooth crown wheel from a 4.08 four speed differential...

    I've done this before too and it does work, but theroretically could lead to mesh differences as the CW&P come as a lapped pair from the factory... though I've had no problems mixing and matching as both parts were in good condition.

    74 casing is a little different too, the area where the pinion bearing fits in the post 75 gearboxes is taller inside the bellhousing, thats why the clutch pressure plate (38mm tall and 45 mm tall) and flywheel (for the different heights of PP) are different, to clear this area (has a coreplug fitted) whereas the later cases don't have the coreplug , it's cast over in alloy, and the casing has less clearance.

    If you wanted to do the conversion it would probably be easier to start with a later model (78 on four speed) gearbox casing, but in the US there is an abundance of x19 five speeds (unlike here in Australia) that it would be simpler to use the later model hubs/axles/flywheel and five speed gearbox complete.

    The modifications to the casing to fit the extension housing are the same for all models of X19, and apply to 128 as well... I've done this to a couple of 3p's too.

    SteveC
     
  16. GregS

    GregS ProjectX

    Location:
    Australia
    5th gear swap

    Hi steve, I just read your interesting articles on 4 & 5speed gearboxes, and was wondering if you may be able to help me out with my dilemma. I bought a used Regata 100S gearbox (same gearing as Strada 105TC except diff) to use the gearset in my X1/9 5 speed box to give a close ratio box for sprints etc. My problem is the fifth gear is a very slack fit, nearly 0.3mm clearance on the lay shaft sleeve, and I am loath to use it, but I haven't been able to find a replacement. What I was wondering was if the X1/9 4 speed 4th gear (ratio 0.959:1) might be interchangeable with the Regata 5th gear which has 47 teeth (ratio 0.959:1). I don't have a 4 speed box in bits to be able to compare them, but if you know how many teeth there are on a 4 sp 4th gear (lay shaft side), and its length and fit on the sleeve etc compared to an X1/9 5th gear (lay shaft) it would help me work out if I can use one, I may have a better chance of finding one than a Regata 5th gear. I have an X1/9 5th gear set I can use if I get stuck, but the 0.863:1 ratio is higher than I would like.
    Hoping you or someone else may be able to help.
    Cheers, Greg
     
  17. Andrew Coles

    Andrew Coles Say no to rice

    Would this be Greg Schultz in Adelaide?

    If so, I've got an X19 4 speed and Regatta 5 speed in a semi dissassembled state at home in the shed - your more than welcome to come around and compare parts if it helps :)
     
  18. Used transmissions and 5 speed conversions

    Good used transmissions are very hard to find. I see you are in Richmond. I have a rebuilt 4 speed that I need to sell if you are interested. I am a couple of hours away in Harpers Ferry.

    As for the 4<5 speed conversion. Yes, I have done a number of these. it isn't hard if you know the issues.

    Its best to start with a '78 4 speed case as they have the larger bolt holes for the 5 speed extension housing. You will need the 4:08 ring gear from a 4 speed to mate with the 4:08 (5 speed pinion shaft) and a complete 5 speed gearset.

    The 5 speed gearset can then be dropped into the 4 speed case along with the shift rails and internal linkages. You can use the 4 speed reverse idler but you will also need the 5 speed pinion shaft bearing that fits in the blind hole in the case as this is a larger ID than the 4 speed.

    You also need to trim the casting ribs near the big end roller bearings to clear the 4th gear shift fork. I also grind the fork down for clearance.

    Mating the 5 speed extension housing is pretty easy assuming you used the 78 case. If not, you need to drill and tap for the 8mm bolts. There is also a dowel that must be sunk.

    After that, it goes together pretty easily.

    I have also converted a few Yugo 5 speeds into X1/9 4 speed cases. Its a slightly different gearset and you can substitute the combo X1/9 4:08 for the Yugo R&P. You cannot use the Yugo 5 speed case in an X1/9 because the shift and clutch linkages don't match up.
     

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