Thread: 300tdi auto gearing optiins

Why would you change either? Going to 3.7 diffs, you will only get about 100rpm higher at 100kph. Not worth it in my opinion.
3.9 diffs would be better though.
Having had a disco1 300tdi, i can feel your pain when it comes to towing a camper, its painful how slow and gutless they are. In the end i gave up and bought a better tow vehicle, then built an isuzu range rover, towing was never an issue ever again.

The 1.4 case makes lockup in 4th come in at about 65 to 70kmh..... and causes a whole heap of extra NVH at highway speeds as you are at about 2700rpm at 100kmh.
Like Damien says, they don't make a fantastic towing vehicle..😑 the 3.9 ratio change would be better, and retain some better low range performance too.

Ashcroft do a 1.3 ratio gearset for the TC, you could put in an atb while your at it - and with your vnt up around 20psi, you should have no problem towing your camper up hill and down dale.

I wouldnt rule out the 1.4, if the vehicle is primarily used for towing a heavy camper. 2700rpm at 100kph is high but its not reving its tits off.

How heavy is the camper?

Camper is not too bad. Ita a jayco half thingy pop top. Not too bad i guess. Car runs ok atm with vnt and large original position intercooler. With the vnt going to 20 psi thats using a boost t piece? Common from supercheap or autobarn?
With my calcs going from 1.2 to 1.4 would set my cruising rpm from 1750 to about 2135. Thats nothing. Did i get my calcs wrong? Thanks for tips. Might be a good idea to raise the boost. Ill try that.
Has anyone changed the air con compressor to an electronic one? Seems like it takes some grunt from the motor when running.
I was thinking upgrading to electronic pump and converting original to air compressor?

I think your calcs are out a bit. Going off ashcrofts ratio calculator, you are doing 2449rpm at 100kph with 1.4tcase vs 2137rpm at 100kph with the 1.2 tcase.

Not sure vern im doing 1750 at 100kph now is that not normal for 300tdi auto? I am running 245 x75.

Here, try it yourself, maybe i have the wrong specs

Ashcroft Transmissions - Ratio Calculator

Fit smaller tyres and it should accelerate faster. I had the same experience with ours. Bigger tyres equals slower acceleration.