87 k5 gear ratio question

[lvwoody]

I am looking at purchasing a 1987 350 tbi. It has 15" 33X12.5 TIRES. It has a 4 inch lift. IT HAD AN AUTOMATIC ORGINALLY WITH THE TRUCK, BUT IT WAS CONVERTED to a manual 4 speed with granny gear.

My question is: Does anyone know what a top speed would be for this truck. I don't know what the gear ratio is, but if occasionly i wanted to put this on highway and do 65-70. what is the highest ratio i would want it? 410, 373, 456, 488? I am driving 7 hours to go buy it and don't want to be disappointed if it tops out at 55. I had a 90 fullsize jimmy years ago with an automatic and i am unfamiliar with this set up.

 

[Ck1500]

hey

most 1987 K5's with the 350 Tbi and 700-R4 transmission stock was 3.42 well thats what mine have been, i have had 3 of them, but i have never converted them to manual though.

hope this helps

 

[4X4HIGH]

It is anyones guess what gears came factory in the rig BUT the deepest stock gearing for a 10 bolt axle is 3.73 and with a 4 speed manual trans and a 33" tire (lets assume 32.5" since tires are generally smaller than stated size) you would be spinng the engine at 2700 RPM @ 70 MPH. That is a little high for fuel mileage but definately not going to hurt anything other than mileage. Keep the speed down at 65 MPH and all of a sudden you're down to 2506 RPM's

 

[6.2Blazer]

It is anyones guess what gears came factory in the rig BUT the deepest stock gearing for a 10 bolt axle is 3.73 and with a 4 speed manual trans and a 33" tire (lets assume 32.5" since tires are generally smaller than stated size) you would be spinng the engine at 2700 RPM @ 70 MPH. That is a little high for fuel mileage but definately not going to hurt anything other than mileage. Keep the speed down at 65 MPH and all of a sudden you're down to 2506 RPM's

Ditto........exactly what I was going to say.

 

[BS_k5]

Doing 70 shouldn't be a problem. Have a 465 4 speed w/ 3.73's and looked down to magically find myself doing about 80