505 GTI diff change
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Thread: 505 GTI diff change

  1. #1
    Fellow Frogger!
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    Default 505 GTI diff change

    Gearing in the GTI always seemed a bit low but I've been too lazy to do anything about it. Not sure what motivated me on Saturday, but I put in a 504 diff that I've had lying around for longer than I've had this 505 (25 years).

    I'll bypass the joys of diff oil running down my arms -- the old syringe is now on the scrapheap -- and get to the point. I'm kicking myself that I didn't do this when I first bought the car. On paper, a change from 4.11 to 3.89 doesn't seem much, just a 5% lift in gearing. Tyre tread depth alone is about 2%. But suddenly, first is a useful gear, and fourth is pretty nice around town. Perhaps I shouldn't be surprised, but going through the gears now feels much more like the old 504. And it's good mental exercise adding 1/20th to the speedo reading all the time too.

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    With the Megasquirt my 505 has a bit more torque than standard and I think the ideal ratio would be the 3.70 diff (code 'M'). I believe this was in some 604s. If anyone has one of these knocking around, I'd be interested in giving it a good home. But if not, I'm still enjoying the longer legs the 504 ratio has given my GTI. Recommend it to others.

    Have fun,

    Rob.
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  2. #2
    Fellow Frogger!
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    Now go to Jaycar and buy a GPS speedo

  3. #3
    1000+ Posts robmac's Avatar
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    Quote Originally Posted by ianrobbo View Post
    Now go to Jaycar and buy a GPS speedo
    https://www.jaycar.com.au/lcd-gps-speedometer/p/LA9025
    Mutual Respect is Contagious


  4. #4
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    Good idea. If I get the 3.7 diff I can add 10% in my head, but I have to close my eyes to add 5% and that might be dangerous.

    Have fun,

    Rob.

  5. #5
    Fellow Frogger! Rally's Avatar
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    I have a 3.7 diff , happy to swap for a 4.11.
    Peugeot 504 Rally car V6
    Peugeot 504 LTI
    Peugeot 504 Ti
    Citroen SM
    Citroen Light 15
    Peugeot 406 SV 5 speed
    Peugeot 307 Wagon
    Toyota Land Criuser V8 Super charged ( to tow the rally car )
    Rally with www.AMSAG.com.au

  6. #6
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    Many thanks Rally; pm sent.

    I took a lie down under my 604 last night, just to see what ratio it had. The table that has been posted here in the past wasn't much help. Checking the 604 manual, the last letter on the side of the diff housing indicates the ratio. On my 604 it's 'R' which stands for 3.58. Other possible endings are 'B', 3.78 and 'C', 3.70. These codes are nothing like the table that has been posted here in the past. Weird that Peugeot did such a good job standardising the diff itself, but couldn't fix on an identification scheme.

    Was toying with the idea of trying out the 3.58 but am very happy that Rally's offer will spare me a double diffectomy.

    Have fun,

    Rob.

  7. #7
    Fellow Frogger! Rally's Avatar
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    Quote Originally Posted by robs View Post
    Many thanks Rally; pm sent.

    I took a lie down under my 604 last night, just to see what ratio it had. The table that has been posted here in the past wasn't much help. Checking the 604 manual, the last letter on the side of the diff housing indicates the ratio. On my 604 it's 'R' which stands for 3.58. Other possible endings are 'B', 3.78 and 'C', 3.70. These codes are nothing like the table that has been posted here in the past. Weird that Peugeot did such a good job standardising the diff itself, but couldn't fix on an identification scheme.

    Was toying with the idea of trying out the 3.58 but am very happy that Rally's offer will spare me a double diffectomy.

    Have fun,

    Rob.
    i have a 3.6 from a 604 and a 3.7 from a 504 Ti and a 3.89 from a 504 carby And a few diesel diffs that I am not sure of the ratios , if you have a preference.
    Peugeot 504 Rally car V6
    Peugeot 504 LTI
    Peugeot 504 Ti
    Citroen SM
    Citroen Light 15
    Peugeot 406 SV 5 speed
    Peugeot 307 Wagon
    Toyota Land Criuser V8 Super charged ( to tow the rally car )
    Rally with www.AMSAG.com.au

  8. #8
    1000+ Posts BIGRR's Avatar
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    My Ti had 3.58 in it for years. Pulled it really well. Until I started towing a 680kg trailer and car (Lots of clutch required off the line).
    Present fleet:-
    Peugeot 93' 205 Gti 16v
    Peugeot 73' 504 Ti from new
    Peugeot 08' 407 Hdi Coupe from new

    Previous fleet:-
    Peugeot 95' 605 Sv
    Peugeot 92' 205 Gti
    Renault 72' 16TS from new
    Renault 69' 10
    Renault 71' 10s
    Renault 68' 10 from new

    "Be reasonable do it my way!"


  9. #9
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    Interesting. I'd have thought the 3.58 would be much too tall. While I don't tow a trailer, I am afflicted with a steep driveway, and the 505 has a slightly taller 1st ratio than the 504 too. Still musing about what would be ideal.

    I took a run up to Bathurst on Thursday. It is interesting what a difference this 5% ratio change has made. Yeah, it cruises 150rpm lower, but the most striking thing is how much wider the apparent gear spacing has become. With the low diff I typically short-shifted my way to 5th, and it was good from about 50kph upwards. With the taller diff, short-shifting is not rewarded; you need to hold each gear for a bit longer so the next gear will be somewhere useful on the torque curve. So the widened gear ratios more or less force you to drive in a more spirited way. 5th feels much more like a cruising speed gear rather than an all-day gear.

    It's definitely an improvement; I just have to unlearn the habits of the last couple of decades and drive it more like the 504.

    Have fun,

    Rob.

  10. #10
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    A quick update on this.

    Took up Rally's kind offer. My old 4.11 is now in pastures green and his 3.70 is back into full time service.

    I installed it on Saturday morning but have only had it for short runs so far. It has further lengthened the car's legs and means 5th is definitely for cruising. 4th is the gear for suburban roads and I'm glad to say that 1st manages my driveway well enough -- it wouldn't want to be much taller. Time spent in each gear away from the lights has been lengthened.

    Very happy with the change. I did get a GPS speedo, but I'm not sure I'll get to like it. Mounting is so-so and power cord isn't pretty. Will see. The mental arithmetic isn't too bad.

    Anyhow, many thanks to Rally for the diff swap. Hope my old diff serves him just as well.

    Have fun,

    Rob.

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