Speedo/10 0ver

[ARTIC]

Just wondering if some one has had this senireo before-89 SURB~SLE 1/2 ton the running gear-front/rear axels/transfer case ect looks stock,but what do i know! i do know some one has been in the rear end,lots of goo around the dif cover,ive had the cover off and gave it a quick visual,no broken teeth,no shavings just dirty oil. some one has done some work to it all so,put the cover back on and filled it up with 80/120. on this truck it has 32x11 tires,witch would means my spedo will be out, over iam guessing.there is no reduction gear on my trany,looks stock,700r4,so i was just wondering why my speedo is 10 over and not 10 or so under,the tranney locks up in #3 @ 32 mph @ 40mph in OD because of the pick in the speedo at the dash.this seems to soon? what did they do the rear end of this truck to make it do that??

 

[southernspeed]

My '78 read 10mph slow with stock 3?? (can't remember!) gears and 33" tires. I put 410 gears in and now it's just 2mph slow (checked with GPS).

I guess the 32"'s are enough to throw yours off by that much.
I think my stock '91 locks in third at around that speed if you're just light on the gas.

 

[84_Chevy_K10]

Most 700s lock in 2nd, 3rd, and 4th, mine did.

Speedo isn't off by a preset number of MPH, but rather the percentage of old tire circumference to new.