I'm confused?? Need some advice please or an explanation??

[Tuomy]

I have replaced my 172cup gearbox which broke with a used 172cup gearbox from another cup. Now I won't disclose speed but the car pulls fine through all gears until 5th gear when it feels like it is struggling and I have lost about 12mph off my top speed in 5th gear. This is very frustrating and confusing as they are identical gearboxs from same model of car!!! I had a new clutch and rear offside wheel bearings replaced at the same time and the car was serviced in april. I can't work out why the gearbox would chop 12mph off my top speed and why it would feel so sluggish getting there in the first place!!! Any help please i'm confused...

 

[E11OOT]

your 1st replacement was probably a PH1 gearbox which is geared longer as opposed to your current gearbox which will be a PH2 gearbox with closer ratios to help move it's lardy arse along the road as quickly as a PH1.

 

[maupineda]

Dont make sense, a shorter 5th ratio would make it faster thru that gear. Problem is not with the gearbox regarding the sluggish feeling you have. As for the gearbox, are you sure it is from another cup? Maybe it was from a 1.6 as they have shorter gearing and the boxes look identical.

 

[E11OOT]

i was only referring to the loss of top end speed in 5th not the problem of it 'struggling'

 

[sideways danny]

new box come from something non-sport before it went in the car you got it from? so 5th is cruise/economy friendly? get the number's off the box tbh

 

[Tuomy]

My car is a phase 2 cup and know the full history of my car. I saw the gear box come out of an identical phase 2 172 cup! Same year, same model car, so surely they should be the same? Took my car back to the garage today they ran a diagnostic and the engine is running without a glitch. So they said it must be the gear box but they can't understand why it would be different either!! It's an absolute mystery.. Can anyone tell me what revs there 172 cup cruises at when you are doing 90mph in 5th gear and 4th gear please?

 

[Russ_16v]

How many times have you tried getting it to top speed mate?

To be honest id like to be its simply the car is not running quite right when you have tried it, it could be that the latest run the air was hotter, maybe tyre pressures down a little, more/less fuel, different stretch of road, or all of the above.

 

[Tuomy]

It's a regular stretch of road I drive on a regular basis, driven the straight literally hundreds of times and irrelevant of fuel level, air temp it hits a certain speed and I checked tyre pressure recently. It is 100% running short in 5th it feels breathless generally when driving. Just frustrated thought I had my car back and it still feels sick!!!

 

[Russ_16v]

lol id check the codes on the box then mate, see if you definately have the right box, there is no difference between the cup boxes so cant be anything like that