how do i find what gears are in the front so i can match the rear

[whiteknight1970]

hey everyone , i just bought an 89 k5 with 350 and 700r trans.
it has a 4inch lift and 35in tires. the previous owner said the gears in the back no longer match the front. the rear was replaced with a junkyard rear. the front gears are the original. can i still drive in 4wd like this??????? if not how do i find what gears are in the front so i can match the rear??????

 

[jim burke]

can i still drive in 4wd like this??????? if not how do i find what gears are in the front so i can match the rear??????

No, you *really* shouldn't (unless the ratios are within about 1% of each other).

One way (the only way I know of to be 100% sure) is to take off the cover and count the teeth on the gears. Example: 41 teeth on the ring gear, 9 teeth on the pinion. 41/9 (41 divided by 9) = 4.56 ratio.

HTH.

 

[mudhog]

take the cover off and count both the pinion and ring gear teath and divide the ring gear by the pinion and no you cant run 4 wheel drive the way it is

 

[UseYourBlinker]

Like said before..DON'T drive it in 4 wheel drive to you figure out what gears you have.

Also fill out your profile,and use the search feature. It work's!

Welcome aboard

 

[87BrnRsd]

Like stated in both of the other posts, DO NOT DRIVE IN 4WD WITH MISMATCHED GEARS!! It will destroy your ring and pinion. Now that I have said that, there is another way to tell the ratio. You can count the number of teeth on the ring and pinion and divide like said before, but tis sometimes hard to see the teeth on the pinion gear to count them. If you take the cover off, there should be a line of numbers stamped somewhere artound the outer edge of the ring gear. It will look something like this:
1Z5768423 7 89 41 10
The first long number (it may have more or less numbers than the example I gave you) is the serial number. The next two (7 89 in this example) are the build date. This would be July of 1989. The final two are the ratio. You take the larger number and divide it by the smaller ratio. In this case, it equates to 4.10's. Since you dont know the rear, you should pull both covers and find each gear ratio. That way you can keep the lower ratio, and upgrade whichever axle has the higher ratio.
It is possible that your blazer still has the factory options list in the glovebox. Check on the inside lid of the glovebox for the options list. It will tell you your original factory ratio. This works but I would check the ring gear if I were you. It sound like whoever you got the truck from didnt know either gear ratio, and who know what has been replaced.
-Harrison