5th Gear at 5000 RPM and 35mph

[AZHomesteader]

My Buddy just called me up, he bought a 90 K1500 Shortbox that has a 5 Speed Manual Transmission in it, I am assuming it's original, An engine from a Pre 79 Vehicle in it (305 from what I can tell) and he said he was out driving it today (Guy said he just put a new clutch in it) and it's Doing about 5000 RPM on an aftermarket Tach, about 40 Mph or so and in 5th Gear? Not sure of the Transmission Type as I am not usually a Chevy Guy and the Stamping on the Side of the Transmission says GM 8672306, Guy that put the clutch in also said he refilled the Transmission with 75-80 Weight Oil. Anyone ever run into a Truck that is THAT geared so Low that Only 45 MPH could be attained in 5th Gear and running close 5k on the Tach?? Something doesn't sound right on this. Waiting for him to Get home now and call me to find out if there is a sticker in the Glove Box identifying the transmission. He lives on a Indian Reservation out here and This Truck is a Frankentruck and been Cobbled together from Gawd Knows how many other vehicles.

 

[stutaeng]

Definitely sounds like something is not right. Do those have a 4Hi/4Lo? Maybe it's stuck on the 4x4 low speed? Although you'd definitely can hear the difference in sound when 4x4 is engaged...

 

[GoToGuy]

Even in low range 5 at 5000 rpm it would be faster than 40. Is the trans 5 speed road gears or 1st granny and 4 road? Tried cycle in and out of 4 low 4 high 2 high? Are 1 through 4, shifting normal rpm at normal ground speeds? And the clutch is correctly adjusted? Using correct shift pattern? Just some ideas?

 

[yevgenievich]

Truck with nv4500 and low range selected at 5000 rpm in 5th would be around 50mph. Assuming 4.11 rear end ratio and 31" tire

 

[PlayingWithTBI]

Maybe the aftermarket tach is set for 4 or 6 cylinders?

 

[618 Syndicate]

Maybe it's stuck on the 4x4 lo?

^^This.

Maybe the aftermarket tach is set for 4 or 6 cylinders?

^^Or this.

Does it sound like it's turning 5k?

 

[AZHomesteader]

It doesn't Sound Like it's Running 5k To me. When it's Idling the Tach shows 1000 Rpm and Not aroun 750 like it should. It's a Manual Shift 4 wheel Drive (lever) and it's in the 2 Hi Position. It does have 15 Inch Tires on it with 31x10 Tires on it. I went over today and test drove it and MPH would NOT go over 45-50 MPH and I had the Accelerator Floored. Not sure what the rear end is geared at. Hell, not even sure if the rear end is original. Like I said, the engine is pre 79 as it has the Dipstick on the drivers side versus the passenger side, the alternator is jerry rigged up for a KILL switch because the ignition switch won't shut off the truck, the Power Steering Pump when Ordered for the Truck was completely wrong for what was on there, no way it would mount due to the return line being in the wrong place, so ordered one for a 76 Monte Carlo that came close but still no cigar, back of pump was fine but bolt holes on front were off to the Mounting Bracket wouldn't work. UGh. This Truck is a nightmare, 95% of the wires are CUT or Missing. 4 Wheel Drive Doesn't work, Per using Jacks and All 4 wheels off ground and shifting it to 4 Lo or 4 Hi. (I think his actuator is bad)

How would I be able to tell on the tach if it's set for 4 or 6 Cylinders and not 8?? Never dealt with an aftermarket tach before. Clutch is correctly Adjusted. 1st gear I am assuming is a granny gear because it barely moves the truck, Shift Pattern is Correct. I assume when he called me that he might have misshifted and was in 3rd Gear instead of 5th Gear by mistake.

 

[GoToGuy]

The tach should be the easiest problem. What's the brand? Gotta a photo? Some have a slide switch. The old 4 inch Sun tach in chevelle had 3 transistors, cut 1 out for 6, cut 2 out for 4 cylinders. Thats one example. Do a online search for the brand and model number, if its not listed or similar an email can usually get some info. As to the rear axle, what if any history however small do you have. It may come to taking a wire brush to the axle area where part numbers, model numbers and usually ring pinion installed ratio might be located, if your lucky the metal id tag might still be there. Good luck.

 

[618 Syndicate]

If you've confident it's not in 4-lo, and it doesn't sound like it's screaming, the tach is the likely issue.
The advice from @GoToGuy is the same as what I'd give you.

 

[reservoir dog]

The sound of the engine should be the key indicator, I can tell a big difference in my truck just pulling it down to D verses OD, sound and torque. Its 3.42 geared.