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robbie thoreson 09-07-2011 02:05 PM

2.73 gear change
i have a 86 c10 with a cad 425, th400 and 2.73 gears in a 10 bolt with the g80. i was wondering on if i should change the gears or the whole rear. ik it would take a hit to my highway rpm but this is a back roads kinda truck. do the 10 and 12/14 bolts have the same u joints and what is needed to change the ring/pinion? iv replaced centers in fords b4 and built motors. just never had to mess with the pinion. i would like to keep sum kinda locker bc the snow gets deep round here.

American Muscle 09-07-2011 09:48 PM

how tall are your tires. It might be cheaper to just swap out the entire rear end. In some cases it may help your gas mileage becaus the motor is working very hard to pull that heavy truck with such a high gear. 3 08's may be a big upgrade from the 2 73's. 3;42 or 3'55 would be really great and still have decent mileage, but when you decide to go 3;73 or higher you can hang up fuel economy.

robbie thoreson 09-08-2011 10:28 AM

well in the summer i run 255 50 r15 good year eagles but my winter tires are a set of 325/60 r15 bfg r/t. i gust put the winter tires on two days ago. the rear might have to wait tho. yesterday on the way to work the truck wouldent stay in third and i had to manually shift it from 2-3 from stops.

robbie thoreson 09-29-2011 09:10 AM

ok trans is fixed. im still looking into changing my gears. im running a bb in this truck and it will very rarely see the highway, but it will happen and i live in the stix so everything is 55 mph. what gears produce what rpm?

spinn 09-29-2011 07:27 PM

Please remove.

spinn 09-29-2011 07:28 PM

My 85 truck has 305 with 8.5 rear. The 3.73 gears are right, lockup 350C trans is 2800 rpm at 65mph, cruise control on. Feels busy but very cruiseable. Trucks can have long 1 peice driveshafts. Use the OEM aluminum shaft from a 03-05 envoy. They are 9lb 66" 4.5" diameter peices that shave some weight, find them for 50-60 at . The OE cast shaft is a twig and may have a vibration at 3000 rpm cruise. Aluminum is smooth at that cruise. After doing the AL pullies, shaft, and some other rotating wt shaving, you will find a difference in power and mpg.

After switch gears use TCI $45 governor kit to reprogram shift points out to at least 5k rpm.

The BM shift kit for 30 has a HD setting that will increase drive pressure, shifts quick not harsh. That gold modulator spring in kit, gets you back to first from higher speeds, for a knock out kick down passing. Also for fish tailing downshifts around the corners.

Mobil 1 ATF is a good multipurpose fluid.

If you like footbrake driving or slug starts go 2600 stall. Adds a nice dimmension to the launch. Wind it up and let go.

robbie thoreson 09-30-2011 12:43 PM

i dont have a lock up and if i saw 5000 rpm id b replacing rockers. this is a low rpm torque truck. i have a custom driveshaft in it already since a stock piece is to long. thanks for the info tho, didnt know that. im realy wanting to go with a lower gear more pulling power but the pulling power is useless unless i can put it to both wheels uk? i love my gov-lok but at the same time hate how i cant keep both spinning in the top of first bc it disengages. is it worth keeping or should i pull the whole axle and find a diff one

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