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1988 gmc 3500 tranny

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May 30, 2010, 1:17 AM

Post #1 of 2 (1735 views)
1988 gmc 3500 tranny Sign In

i have a 1988 gmc 3500 with a 5.7 and a 3 speed manual w/granny gear.140,000 miles.i drive on the highway a lot and i was thinking of putting a 4 speed or 5 speed in to lower the rpms at highway speeds.can anyone tell me if there is a tranny i can use with the same input shaft size and spline i can use?i am trying use the same clutch because cash is tight.also what problems am i going to cause with gearing issues.i dont know what rear end ratio is,but i can find out.any info would be appreciated.....

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May 30, 2010, 11:54 AM

Post #2 of 2 (1727 views)
Re: 1988 gmc 3500 tranny Sign In

What is the rpms you are getting at 70?
You are probably going want to know your gear ratio for the rear end. Maybe stick some lower ratio gears in there for the freeway of course doing this you'll notice it a little more doggy on the bottom end.

but I'm guessing you aren't worried about the hole shot off the line with this ride.

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