98 Ram 1500 Trouble

[Nick Kuhn]

Hi guys,

Not much of an auto guy here. Took my brother's truck up to lake for the weekend. I believe it's a 4 + OD automatic. What I found out is from it's final (OD) gear it would not shift when climbing a hill unless you really floored it, and when it did it would shift 2 gears. This made towing the boat especially annoying. Also when you gave it a little gas when in the final gear it would change the blower from the dash to the defrost. My best guess is bad vacuum hoses. Any other ideas (throttle related maybe)? Otherwise the engine runs fine, and the transmission itself shifts well when it does finally decide to shift. Just looking where to start trouble shooting.

[PurpleFloyd]

I had that same kind of truck and it seems to me you might have a vacuum problem. Mine actually had that same issue with the heater/ defrost but the mechanic never found the source.

The transmission issue might just be an adjustment to the linkage that controls the downshift. I know when I had mine rebuilt if I really kicked it down it would downshift and then shift down again and the rpms would spike so I took it back in and they made an adjustment and it worked correctly.Was the trans worked on at any point?

[Jeremy airjer W]

I have been thinking about this since you posted it and I knew I had ran into a simular problem many years ago. Then it dawned on me!

There is a vacuum chamber under the passenger side cowl (under the wiper blades). Make sure that vacuum chamber is able to hold vacuum. You can test it with a vacuum pump. It should hold vacuum for a long time.

If it does and your vacuum pump has a built in gauge place it on the vacuum line that connects to the vacuum chamber that goes back to the engine. Start the engine. it should read 20" of vacuum or so. Shut the engine off. It should continue to read 20" of vacuum. If it drops than the one way valve somewhere between the vacuum chamber and the intake is bad.

You can test this with the vacuum pump as well. It should allow air to pass when vacuum is applied on one side and not allow air to pass when applying vacuum from the other.

Solve the vacuum issue and the other issue will likley be resolved.

[Nick Kuhn]

Was the trans worked on at any point?

The previous owner had a new transmission installed about 10k miles before my brother bought it. So maybe 30k miles ago was the last time it was worked on.