Quote:
Originally Posted by RRPhil
Based on 275/40 R20 front & 315/35 R20 rear tyres the rolling radius is around 361mm
Axle ratio for the 4.6iS is 3.9091 (i.e. 43/11)
The transfer box ratio is 1:1
4th gear ratio for the 5HP24 is 1.0000, and 5th is 0.8037
Hence, the driveline is geared at 21.6mph/1000rpm in 4th and 26.9mph/1000rpm in 5th
At 50mph, with no converter slip, that’s equivalent to 2310rpm engine speed in 4th and 1860rpm in 5th
At 60mph, with no converter slip, that’s equivalent to 2775rpm engine speed in 4th and 2230rpm in 5th
Clearly, in addition to the accuracy of the speedo which will be between 3% & 5% fast, the main problem is the fact that, in failsafe, the lock-up clutch is unlocked in the torque converter.
To get zero slip across the converter requires a fine balance between drive & overrun which isn’t easy to achieve on the road when there’s traffic to think about as well as gradients, speed limits, etc. but maybe it’s worth trying to drive at a steady 50mph or 60mph and reading off the engine speed to see which gear it corresponds with?
Phil
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My main concern with trying that is that it’s at least 2 mile of stop/go lots of traffic lights and roundabouts to get to a busy dual carriageway. If the drum has gone how much additional damage might that cause as well as all the slippage to clutches. It is about the same distance of 2 mile to a transmission repair centre who have diagnostics, would the diagnostics they have be able to tell which gear it’s in and do an accurate assessment of the problem. I’d rather run the 2 mile and pay the roughly £100 fee than risk further damage potentially spreading all those bits of metal around.
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