Gearbox / Speedo Issue

[Alic01]

Hi all, I have had a read round and a good search but I wonder if you could point me in the right direction.

I bought my Ph1 172 a couple of weeks back and on the way home from the dealers the gearbox blew, I made it 45 miles in my new purchase which was kind of gutting, I had all the service history for the car and its has been so well looked after I fought tooth and nail with the dealer for them to repair it rather than give me my money back.

I have now got the car back with a recon box in it and the speedo is reading incorrectly, its reading about 82ish when GPS says 70 and reads about 38 when GPS reads 30. Unfortunately I didnt have sat nav in the car before the box went to know if it was wrong before it went.

I have read all sorts of information regarding the speedo drive being from the ABS rings but also people saying it comes from a speedo sensor in the diff housing. Could someone please enlighten me and advise if there is anything I can do to get the speedo right.

I did read a post about someone having the wrong number of teeth on an abs ring or damaged rings which have caused similar issue, if they are driven by the rings I will look at this over the weekend.

If its a speed sensor on the diff should I be worried I might have the wrong box? I will never get anyone to admit that now!!

Cheers

Al

 

[Russ_16v]

As yours is a ph1, the speedo read is taken from a sensor in the box.

Is the car standard? Does it have bigger wheels/different sized tyres?

 

[Alic01]

All standard and original, thats what i liked about it!

If its in the box im wondering if i have a Ph2 box then, i know their final drive was shorter wasnt it to get the acceleration back with the extra weight.

Was it shorter by approximately 15% as in this case tho, could have been i guess

 

[Russ_16v]

the only way it could be a ph2 box is if it was a cup box, as they dont have abs so they have a speedo sensor in the box same as the ph1's. the ph2's take the speedo reading off the abs sensors

 

[boomerbang2006]

Dont worry about the gps reading different speeds to the car,dont forget the gps travels to space and back before it shows the speed,the car does it instantly,mines the same.

 

[Alic01]

Cheers for the replies, i understand it would have to be a cup box to be a ph2 box.

Is there anything which can be done to make this right? The difference is not to do with the sat nav signal etc as i have used the same sat nav in about 10 cars before this time all of which read the normal 5-10% slow, I dont want to drive around with the sat nav in all of the time so i would really like an accurate speedo.