Trans gearing change
10-28-2002, 09:05 AM
#1
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Trans gearing change
I have been hearing about the great effects of changing the gearing in the 4 speed transmissions in cars like my '87 930. Has anyone done this? What does it involve? What have been the results?......and finally, at what cost.
10-28-2002, 06:55 PM
#2
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[quote]Originally posted by Louis:
<strong>I have been hearing about the great effects of changing the gearing in the 4 speed transmissions in cars like my '87 930. Has anyone done this? What does it involve? What have been the results?......and finally, at what cost.</strong><hr></blockquote>
Hi Louis:
FWIW,....we have quite a number of these since 1976,....
Since the proper way to do this is to repalce all 4 ratios, this involves replacing the mainshaft and 4 gearsets. 1st gear is machined onto the mainshaft so its replaced whenever 1st gear is altered. Some people have re-welded different ratios onto the stock mainhaft, but this not satisfactory to me at all and makes that part fragile.
The tranny is disassembled, the mainshaft is replaced and all 3 other gearsets. Any marginal operating sleeves, syncros or other parts are replaced at this time as well. This is also the best time to add an LSD, if you do not have one.
With four custom close-ratio gears, the transmission becomes an asset, instead of a liability and the engine will not fall off boost between shifts anymore. The difference in acceleration is astounding,....
A brief breakdown in costs are:
1st gear; $ 1400
2nd-4th gear $ 650/each
Labor; 8 hours
Add some extra for parts if the tranny needs to be overhauled.
<strong>I have been hearing about the great effects of changing the gearing in the 4 speed transmissions in cars like my '87 930. Has anyone done this? What does it involve? What have been the results?......and finally, at what cost.</strong><hr></blockquote>
Hi Louis:
FWIW,....we have quite a number of these since 1976,....
Since the proper way to do this is to repalce all 4 ratios, this involves replacing the mainshaft and 4 gearsets. 1st gear is machined onto the mainshaft so its replaced whenever 1st gear is altered. Some people have re-welded different ratios onto the stock mainhaft, but this not satisfactory to me at all and makes that part fragile.
The tranny is disassembled, the mainshaft is replaced and all 3 other gearsets. Any marginal operating sleeves, syncros or other parts are replaced at this time as well. This is also the best time to add an LSD, if you do not have one.
With four custom close-ratio gears, the transmission becomes an asset, instead of a liability and the engine will not fall off boost between shifts anymore. The difference in acceleration is astounding,....
A brief breakdown in costs are:
1st gear; $ 1400
2nd-4th gear $ 650/each
Labor; 8 hours
Add some extra for parts if the tranny needs to be overhauled.