86 K5 4spd what gears would i have

[84CUCV]

I was told 3.08s, but i dont see how that could be. My cucv has a 400 and 3.08s. So what would i have? Should i stop being lazy and go pull the cover? Just need to know. I would like to run 35" bfgs for now with stock gears.

As always thanks for the help

 

[84CUCV]

anyone

 

[tRustyK5]

My '81 was a factory 465/208 truck and it came with 2.73's...so yeah, I'd pull those covers and find out for sure before slapping some 35's on it.

Rene

 

[84CUCV]

so if it is 2.73s what will happen if i do put on 35s? to much rpms? thx rusty

 

[ryoken]

too little....

http://www.florida4x4.com/tech/gearcalc.php

 

[84CUCV]

not to sure i get you, dont know much about gearing yet. Could i get away with 33s? thx

 

[berserker]

old school

jack up the rear end so both wheels are off the ground then turn one wheel by hand one full rotation and count how many times the driveshaft spins that will give u a rough estimate

if the drive shaft spins 3 times you probably have 3.08 gears if its just under 3 times its probably 2.73

​

youll should be fine with 35's with 10 bolt axles you will wany some gears though

 

[BowtieBlazer]

for what its worth my stock 84 w/4spd had 3.73's i was suprised felt like 3.08's

 

[84CUCV]

OK so 3.73s, 2.73s and 3.08s are all highway gears? so i think the truck would be real slow with the 35s. am i thinking right or way off? thx for the help

 

[BowtieBlazer]

I ran mine with 3.73's and 35's and it wasn't bad. 4.11's woke it up some. Just don't go too deep in the gearing if you plan on running much interstate

 

[tRustyK5]

With 2.73's and 33's I used to have to use granny low gear as a regular first gear to get the truck moving. The only upside was it was pretty good on fuel mileage on the highway...was only turning 1750 rpm on the highway. When I swapped to 3/4 ton diffs they had 3.73's which was much better. I ran 35's with the 3.73's and it was fine with the 4 speed.

Rene

 

[84CUCV]

Ok thx for the replys, i think i got it.

 

[Creek]

Check the inside of the glove box lid for RPO codes.

RPO FY LY DIVISIONAL RPO DESCRIPTION
GS4 85 86 AXLE,RR 3.70 RATIO
GT4 76 88 AXLE,RR 3.73 RATIO
GT5 76 88 AXLE,RR 4.10 RATIO
GT8 76 88 AXLE,H.D. RR 4.10 RATIO
GU1 76 87 AXLE,RR 2.41 RATIO
GU2 76 88 AXLE,RR 2.73 RATIO
GU3 82 85 AXLE.AR 2.93 RATIO
GU4 76 88 AXLE,RR 3.08 RATIO
GU5 76 88 AXLE,RR 3.23 RATIO
GU6 76 88 AXLE,RR 3.42 RATIO
GV4 82 87 AXLE,RR 3.36 RATIO
GV8 82 85 AXLE,RR 2.72 RATIO
GW4 84 85 AXLE,RR 3.31 RATIO
GW6 85 88 AXLE,RR 3.27 RATIO
GW9 76 88 AXLE,RR 2.93 RATIO
G80 76 88 AXLE,RR LOCKING TYPE
G83 82 83 GEAR,RING 8.75 IN
G87 76 87 GEAR,RING 8.50 IN
G88 76 83 GEAR,RING 8,875 IN
G89 76 87 GEAR,RING 7.50 IN
G92 76 88 AXLE,PERFORMANCE RATIO
G95 85 88 AXLE,ECONOMY RATIO

 

[dyeager535]

Go check dremu's brochure pages. I'll bet money that there probably aren't more than 4 possibilities that year:
2.73 maybe, 3.08, 3.42, 3.73

It seems that later years didn't even bother with 2.73's, but they did hang on for awhile. Nowhere near as common as 3.08's.

As an edit, I don't see that available gear ratio's are shown in the brochures for '85 or '86, at least. ('81 looks like the last year that gear ratios were important enough for owners to know)

 

[84CUCV]

thx guys i will find out.

 

[84CUCV]

damn they are 2.73s thx for the help

 

[BKinzey]

Hmmmm. My 87 w/ 700r4 has 4.10s

 

[84CUCV]

4.10s from GM? never knew that one for a k5

 

[BKinzey]

OOPS! I'm lying The RPO code says 3.42. Previous owner said 4.10

What does the FY & LY stand for?

 

[tRustyK5]

First year, Last year

Rene