Results 1 to 9 of 9
  1. #1
    Join Date
    Oct 2016
    Location
    Madrid
    Age
    42
    Posts
    14

    Problem with final drive gear speedometer (sierra cosworth tremec + stewart warner)

    Hello everyone,

    I have a problem with reading the speedometer (it marks me much less speed than the one I actually go).


    My gearbox is a T5 tremec from a 1987 Ford Sierra cosworth , my rear differential is 3.08 (jag unit) and my wheels are 15 inches with 235/60 (it's a DAX).

    The problem I have is that the final speedo drive gear (which is inserted in the gearbox) is too large (it is from the 1987 ford sierra cosworth). I have tried to buy in the USA a new final drive of tremec T5, but it is not valid (attached picture, the one I bought is the white one), since those are made for tremec from USA (mainly mustang). Does anyone know what I can do to get a correct reading on the speedometer?

    Thank you!

    P.D: My speedo is a mechanical stewart warner unit (cable operated)
    Attached Images Attached Images

  2. #2
    Join Date
    May 2004
    Location
    Cowbridge, United Kingdom
    Age
    60
    Posts
    9,819
    I had a similar issue on my Contemporary, I ran out of available ratios for the speedo driven (like your white one).
    I had all the different colours but could not get the speedo correct enough.
    Eventually I changed to an electronic speedo which I could calibrate as required.
    That was on a TKO 600 gearbox and jaguar 2.88 diff.
    Kev Davies
    South Wales Area Rep. UKCC Membership Secretary
    DAX Mk4, 383 Chevy Stroker, Tremec. SOLD
    Contemporary CCX 3-4028, 445ci Big Block FORD FE,TKO 600, Old School IVA'd and SOLD
    Dax De Dion LS2 and T56 IVA'd June '17 SOLD
    1965 Ford Mustang 289 Convertible

  3. #3
    Join Date
    Feb 2011
    Location
    Devon
    Posts
    259
    The one you’ve bought is ok for a T10 gearbox, a quick search on google gives you driven gears which look the right type for T5 gearboxes. You need to know the number of teeth of the drive gear and then you can work out if there is one with less teeth than your present one. There are a couple of sites that can calculate the correct driven gear with your ratio and tyres etc.

  4. #4
    Join Date
    Oct 2016
    Location
    Madrid
    Age
    42
    Posts
    14
    Thank you Mitch.

    I did the maths and I need a 17 teeth drive (in fact the white one is a 17 teeth one). Where can I buy one that works in to a Ford sierra cosworth gearbox? (I am unable to find where)

  5. #5
    Join Date
    Feb 2011
    Location
    Devon
    Posts
    259
    Hi there, these look like they should work, as far as I know, but check first.

    https://transmissioncenter.net/shop/driven-gear/

  6. #6
    Join Date
    Oct 2016
    Location
    Madrid
    Age
    42
    Posts
    14
    Thank you Mitch,

    I emailed them to ask if they can help me.

    Thank you again.

  7. #7
    Join Date
    Feb 2011
    Location
    Devon
    Posts
    259
    Hi, a bit more research indicates that the T5 sierra box has a different drive position, so the gears are cut differently.
    Apparently it can be adapted using Land Rover drive gear and modifying a Borg Warner 35 holder.
    Sorry not an easy fix.

  8. #8
    Join Date
    Mar 2007
    Location
    Lincolnshire
    Posts
    312
    I am running a Smiths mechanical gauge and Cosworth T5 box. No idea what the drive wheel in the box is but i just had the speedo calibrated by Speedy cables to suit the diff / wheel / final drive combination. Tested on a rolling road it was accurate at every 10 mph increment up to 100. Would it be worth talking to Speedy cables regarding your Stewart Warner gauge to see if it can be calibrated?
    Crendon 427 Chassis no. 10 - 351 Cleveland. Tot Rod mini me.

  9. #9
    Join Date
    Oct 2016
    Location
    Madrid
    Age
    42
    Posts
    14
    Quote Originally Posted by Yellowbelly View Post
    I am running a Smiths mechanical gauge and Cosworth T5 box. No idea what the drive wheel in the box is but i just had the speedo calibrated by Speedy cables to suit the diff / wheel / final drive combination. Tested on a rolling road it was accurate at every 10 mph increment up to 100. Would it be worth talking to Speedy cables regarding your Stewart Warner gauge to see if it can be calibrated?
    Thank you Yellowbelly! I will try to contact them.

    Just to inform you: I spoke with the guys from "transmissioncenter.net" and they told me that those final drive gear in metal no longer made by anyone, and that they could not give me any solution since it was a very unknown piece for them (for them a sierra cosworth is something very rare)

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •