Torque Converter Upgrades
The ZF auto as used in the LandRover vehicles uses three different diameters of torque converter. Small. Medium and Large.
"Small" is used on the 300 Tdi, P38 diesel and the TD5. "Medium" is used on the 3.9, 4.0 and the later 4.6 P38. "Large" is used on the early 4.6 P38"s. Note the large converter can only be used with the stage 2 as it will only fit the 4HP24 front end.
A larger converter is desirable on a tuned engine for a few reasons :
1) Lower stall speed, there's little point in having a nice torquey engine if the converter is not transferring the drive and you are revving straight past it. A larger converter will reduce these revs and allow you to take up drive earlier which results in much more relaxed driving. This is by far the biggest advantage of upgrading the converter. Note these reduced revs are not to be confused with lower gear shift points, these stay the same as they are determined by the autobox ECU programming.
2) Less heat generation because of the lower stall speed and reduced 'slip'.
3) The converter has a lock up clutch inside and the smaller one struggles to cope with a stock engine, never mind a tuned one. This clutch can slip as you accelerate when it should be staying locked. In a TD5 the stock converter is the small one. If you have a stock engine, stick with the stock converter. If the engine has a mild tune then we would recommend upgrading to the medium diameter one, we have sold quite a lot and get very good feedback.
			
		
 
	
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