Automatic, Manual, Petrol Diesel?

[Rover 75 Man]

Hiya guys, just a quickie........

A Manual or Automatic Gearbox does it matter if its from a Petrol or Diesel vehicle?

I mean can an Automatic Petrol Gear Box be used in an Automatic Diesel car and vice versa?

Thanks every one

[trikey]

They are all different I'm afraid!

[James.uk]

Auto boxes for petrol engined cars have much higher gear ratio's than those used in diesel powered cars..
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[SD1too]

John,

I am able to explain in more detail from MG Rover data.

The JATCo transmission for the K1.8 & KV6 2.0 litre engines shares the same gear ratios as your M47R diesel except for the final drive. This is 3.45:1 on your car but 4.15:1 on the petrol models I have quoted. This would lower your road speed by about 5 mph at 1000 rpm in top gear; quite a difference.

If you have a fault with your automatic transmission did you know that the two known weak points (solenoids and reverse piston) can be repaired without removing the gearbox from the car? It is also recommended to stick to the specified type of transmission fluid. Many garages do not.

Simon.

[James.uk]

That doesen't seem to make sense??? My car is only revving at 2150 in top at 70 mph. I bet the petrol engines are doing far more than that?

And I doubt the revs are comparable at any speed in any gear??? E.G. 3rd gear at 70 mph my diesel would be doing approx 4000 revs.. ?? Is that the same for a petrol engines?

If it is correct, then I want to swap my auto gearbox for one meant for a petrol engined car.
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[Rover 75 Man]

Thanks everyone that has been a great deal of help.

[SD1too]

Originally Posted by James.uk

That doesen't seem to make sense??? My car is only revving at 2150 in top at 70 mph. I bet the petrol engines are doing far more than that?

Yes, they will be, because the final drive on the petrol engine gearbox is lower geared (or higher ratio if you prefer to think of it that way). My 2.5 litre V6 runs at 2,500 rpm for 70 mph in fifth gear. The figures say that the other petrol engines will be at 2,700 rpm.

And I doubt the revs are comparable at any speed in any gear??? E.G. 3rd gear at 70 mph my diesel would be doing approx 4000 revs.. ?? Is that the same for a petrol engines?

No, it won't be the same. The final drive ratio affects the relationship of engine speed to road speed whatever gear the transmission selects. On top of that, the 3rd. gear ratio is different on the 2.5 litre KV6.

All this can get very confusing. Put simply, if the OP puts any of the automatic gearboxes designed for petrol engines into his diesel, his engine speed will be higher at any given road speed.

Simon.