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89 K5 350 700R4 Silverado Edition- Gears

G

GalDemSuga

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ATLANTA, GA
Does anyone know what gears came in this truck from the factory. I need to replace the rearend and dont want to be wrong on my purchsae.

I may get a set for the front and the rear.
 
My 89 blazer silverado came with 3.73's and 31" tires factory. Your best bet is to pull the diff cover and count the teeth on both the ring and pinion and do the math (divide the ring gear tooth count by the pinion tooth count) this is the ONLY way to be 100% sure.
 
4X4HIGH said:
My 89 blazer silverado came with 3.73's and 31" tires factory. Your best bet is to pull the diff cover and count the teeth on both the ring and pinion and do the math (divide the ring gear tooth count by the pinion tooth count) this is the ONLY way to be 100% sure.
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I was told that they were 3.73 and the truck did have 31's when I got it. I upgraded to 33's and drove it that way.
 
On another note, I do alot of highway driving during the winter months. Is there a set of gears better suited for this whlie being able to handle snow/mud etc?
 
4X4HIGH said:
My 89 blazer silverado came with 3.73's and 31" tires factory. Your best bet is to pull the diff cover and count the teeth on both the ring and pinion and do the math (divide the ring gear tooth count by the pinion tooth count) this is the ONLY way to be 100% sure.
Click to expand...

Also, what was your spline count, 30 or 28?
 
4X4HIGH said:
Assuming you're talking about rear axle spline count and mine were 30 spline which is what GM changed to starting in 1988/1989
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Ok. Thanks:)
I will look around for deals on 4.10 gears.

Would the front axle also be 30 spline?
 
GalDemSuga said:
Ok. Thanks:)
I will look around for deals on 4.10 gears.

Would the front axle also be 30 spline?
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If it's an original axle it will also be 30 spline. The bad thing is that the 30 spline axles are marginally stronger than a 28 spline BUT all GM did was to bore the carrier to fit the larger 30 spline axles so now you have a stronger axle and a weaker carrier. Also if you ever need replacement axles there are FAR fewer since you're limited to 1988/1989 and later.
 
What would be the effect of running 3.08 gears with 33" tires with a 700R4 tranny?

I ask because I do 90% of my driving on the interstate and 10% offroad. The current setup is 3.73 gears with 33" tires and 700R4 and I average 10-12 MPG.
 
In my opinion 3.08s and 33s would make OD pretty much useless , not help fuel economy and shorten the life of your trans.
 
big rig + big tires + highway gears + 700r4 = death in the end.

covered here tons of times. when od tranny auto go as deep as you can but still keep it with in range. or the tranny cycles 4th to 3rd to 4th to 3rd and hunts for gears basicly.

this creats heat and frys the tranny.

like scott (4x4high) said 4.10 would prob be best in the end for your driving or if on the cheeper. new 3.73 for the rear only and be done like you never changed a thing.
 
With 33's and a 700r4 I vote 4.10's also.... this calculator isn't perfect but it'll get you in the ballpark. All three of these are at 70mph and 33" tires the first being 4.10's then 3.73's then 3.08's.
With 4.10's you'd only be around 2k rpms at 70mph which is perfect IMO.

gearing-1.jpg
 
I see both sides of the conversation here... if you're going to go with 4.10's it would be easier/cheaper to find a set of 3/4 ton axles with 4.10's already in them and toss them under your truck. That being said for what you do 10b's are fine and offer more clearance and are lighter which should minutely help with mileage.
 
Avery4jc said:
I see both sides of the conversation here... if you're going to go with 4.10's it would be easier/cheaper to find a set of 3/4 ton axles with 4.10's already in them and toss them under your truck. That being said for what you do 10b's are fine and offer more clearance and are lighter which should minutely help with mileage.
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that is precisely why i'm so iffy on this decision. i want good mpgs and still go offroad:)

Thanks to everyone for the great advice and support:)
 
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