To Do List - Advice?

[Juke22]

Hi All,

I'm pretty new here, got my truck inspected and plated, and been driving it past few months. There's a list of projects I'll write below, hoping to get some advice to get me started. Previous owner says it has a 305 engine, 1986 High Sierra K2500.

Transmission:

1) The TH400 automatic transmission kicks pretty hard when shifting between P, D, R. It also kicks when shifting up gears while driving.

It's leaking ATF pretty bad from the output shaft, and slightly from the pan bolts, so i'm planning to replace the fluid with correct GM fluid (which is?), and also replace the filter, seal, & pan gasket.

The ATF looks very clean, and maybe overfilled, so i suspect previous owner tried to fix the hard shifting problem. The vacuum modulator also looks shiny clean, so I may try adjusting that first counterclockwise two turns, or replace it and clean the valve inside.

Carburetor:

1) I cleaned and rebuilt the Edelbrock 1406, there was encrusted dirt in the float bowls, and one of the metering rods was missing a spring and seized shut. After tuning the carburetor and idle, the transmission kick was slightly less.

2) I'd like to replace the vacuum lines, something I noticed is the distributor vacuum advance is connected to the manifold vacuum (driver side), and the transmission vacuum is connected to the timed vacuum (passenger side).. i think this is wrong, but when i switched them the engine idled poorly. I need to figure out how the transmission vacuum routes through the firewall.

Timing:

I'm thinking of getting a all new distributor, wires, and plugs. I think the original GM HEI distributor is still in there. Is it okay to put a new distributor in an old engine? Are those $300+ ones on Summit Racing worth the money?

Dash Gauges:

1) Oil Pressure gauge stuck on the 3 O'clock position, or slightly past the 60psi mark. I replaced the sending unit on the engine, but nothing changed.

I also noticed there's another connection on the brass elbow that has nothing connected to it. What's supposed to connect there?

2) Temperature gauge jumps to 200 degrees and just bounces all over the place with the engine rumbling.

3) Fuel gauge only goes up to about 3/8 on a full tank and E for empty, it kinda works, but is not using the full range of the gauge. I recall testing the resistor and thinking it might be bad.

i need to go follow the troubleshooting videos again with my voltmeter and report back, but maybe you have some ideas.

4) Speedometer seems to read inaccurate +/- 20mph, although it is connected and working; it bounces around quite a bit. It says i'm doing 85 while everyone is flying past me. Will replacing the cable fix it?

Body:

What is the best way to preserve its current condition? The doors and cab corners have a bit of rust, but overall in very good condition. Can i wax it, or is it already too late?

Thank you

I think i wrote too much, no one is going to read this.. i got a lot of work to do!

 

[Matt69olds]

The transmission should be on full time manifold vacuum. Don’t mess with the modulator until the vaccum lines are sorted out.

I wouldn’t replace the distributor, repair or replace what’s worn.

Unplug the oil sender, ground the wire. Turn on the ignition , the gauge should read zero. With it not grounded, the gauge should read well beyond 60psi. If that checks out, either the engine has phenomenal oil pressure sender, or you got a bad sender.

If the dreaded tin worm has moved in, it’s too late to prevent rust, all you can do is prevent future rust. Go to your nearest automotive paint supply paint supply store, get a couple cans of internal panel costing. Spray it in the rockers, cab corners, body mounts, anyplace you can’t reach to clean, but dirt and water can collect. Start saving for future rust repairs.

 

[edgephoto]

A transmission fluid and filter change is a good idea. Do not waste money on the crappy auto parts store cork or paper gaskets. They will leak. Spend the money on a lubeLocker gasket. When the pan is off take a ball peen hammer to each bolt hole and bend the hole flat or a tiny bit toward the outside. This will ensure a good seal when you torque it.

As for the leaking output shaft seal. It could be just a tired seal, worn bushing or it could be a groove worn in the yoke where the seal rides. You will have to diagnose which it is. You can buy a repair sleeve to install wear the seal rides on the yoke to give the seal a "new" surface to ride on. They are easy to install and are dirt cheap.

These old girls take Dexron III fluid. The newer stuff is backward compatible although some will argue not. Read about it and make your own decision.

If you buy a new distributer stick with stock HEI. HEI was a very good system and unless you are revving at crazy high RPMs you wasting your money on "speed" parts. Personally, I would just replace the cap, rotor and coil. Inspect the rest and replace as needed.

Your speedo bouncing is a dry old cable. Replace it and then see where your speed reads. You will have to replace the driven gear at the transmission to change the calibration.

You oil pressure gauge....get a manual gauge and read the actual pressure. Then do the test as directed above.

Your temp gauge, fuel gauge, and oil pressure gauge could be as simple as a bad ground. Just do basic electrical testing to diagnose it. These three issues are most likely related vs. three separate problems. Electrical diagnosis is super easy. Grab a wiring diagram and make the tests. If you need help we are here.

 

[HotWheelsBurban]

A transmission fluid and filter change is a good idea. Do not waste money on the crappy auto parts store cork or paper gaskets. They will leak. Spend the money on a lubeLocker gasket. When the pan is off take a ball peen hammer to each bolt hole and bend the hole flat or a tiny bit toward the outside. This will ensure a good seal when you torque it.

As for the leaking output shaft seal. It could be just a tired seal, worn bushing or it could be a groove worn in the yoke where the seal rides. You will have to diagnose which it is. You can buy a repair sleeve to install wear the seal rides on the yoke to give the seal a "new" surface to ride on. They are easy to install and are dirt cheap.

These old girls take Dexron III fluid. The newer stuff is backward compatible although some will argue not. Read about it and make your own decision.

If you buy a new distributer stick with stock HEI. HEI was a very good system and unless you are revving at crazy high RPMs you wasting your money on "speed" parts. Personally, I would just replace the cap, rotor and coil. Inspect the rest and replace as needed.

Your speedo bouncing is a dry old cable. Replace it and then see where your speed reads. You will have to replace the driven gear at the transmission to change the calibration.

You oil pressure gauge....get a manual gauge and read the actual pressure. Then do the test as directed above.

Your temp gauge, fuel gauge, and oil pressure gauge could be as simple as a bad ground. Just do basic electrical testing to diagnose it. These three issues are most likely related vs. three separate problems. Electrical diagnosis is super easy. Grab a wiring diagram and make the tests. If you need help we are here.

I'll add in, the Blue Streak cap and rotor have brass contacts and better plastic. We ran those on all our square body trucks and Burbs (8 total) and on our Buick LeSabre Estate Wagon too. Coil in cap HEI, I would not use anything else.