1987 Gmc Sierra 1500 4x4

green 788 · November 23, 2009

My friend found a really nice 87 Sierra 4x4 the other day... half ton, long bed, 305 V8, newly replaced with a crate motor. It's an automatic tranny... It was a North Carolina truck, and they don't salt the roads down there in the winter where this truck came from, so it's amazingly clean and virtually rust free on the undercarriage.

We just had some questions about the truck.

What transmission is this? It's a 3 speed (not an OD). Is it a TH350, or something else?

The truck has twin tanks, and the right side tank has a bad fuel pump. (Truck is a throttle body injection). Are these fuel pumps integral with the sending unit (like many of the late 80's early 90's), or can the pump be replaced without having to buy the whole pump/sending unit?

Are there any known weak points with this truck (like transfer case, 4x4 components, transmission, electronics, etc.)?

Thanks for any advice or comments.

Dan

Stevens03 · November 23, 2009

The engine is weak.. otherwise, a pretty solid truck from my experience. Theres a million bolt ons to help the little 305.. but it will never run like a 350. Its just underpowered for the size of truck.

Luvbelly · November 23, 2009

Sorry no answers to your questions but a comment. My first truck was a 73 K20 with a 350. I absolutely loved that truck full time 4wd and all. If they still made that body style I would own one. Always liked them, always will. If you can post up some pics. I only had one truck with the 305. It was a 98 K1500 extended cab. Not sure what changes occurred over the years but the motor was adequate for the truck. No speed demon by any means but I never hung my head in shame either.

grampadirt · November 23, 2009

You can tell which tranny your friend has by the shape of the pan.....

TH350

Th400

most likely it's a TH350.I can't see GM putting a TH400 behind a 305 engine

I replaced my fuel pump last year on my '95,only changed the pump,nothing else.Prolly the same on the older trucks.

green 788 · November 23, 2009

I drove the truck back from the town where he bought it from... and it actually seems to have a good amount of power, but it's geared LOW... runs at pretty high RPM (no tach, not sure exactly what RPM) at highway speeds. Guessing, it's probably turning 2500 to 2800 rpm's at 65 mph.

It's got the G80 option, so it shouldn't have any trouble getting stuck.

If he can get me some pictures, I'll put 'em up. Maybe he'll drive it by here and I can take some. It's a really solid truck, two tone, tan and maroon...

My '96 K3500 has the vortec 350, which many say is weak for it, but with its 4:10 gears, it pulls my 7000+ pound camper about as well as you'd want it to, up some steep hills I was keeping up with a built Ford 351 pushing supposedly 300+ horsepower, and his trailer was about half the weight of mine.

Thanks for the replies... it probably does have the TH350, which is a great tranny in its own right.

Dan