Do a compression test both wet and dry and see how the rings are.

I never liked the fact that they used the 3.55 gearing and I think that is most of your issue. Even my truck would downshift on hills that it shouldn't but after I went to 4.10's it all went away. My dad had a 1995'ish with the 5.9L and 3.55's (same same) and that thing was a gutless wonder.....My 2 cents

 

This is going to be a basic question, but how did you go about checking for the code?

I mean after you shut off truck, then scan or did you have scan on while driving?

thanks

 

dont jus cut the cat out, get either a jegs y pipe or duels, i put on my jegs y pipe ith a bad plenum and i could feel that the truck had way more power

 

The gearing wouldn't bother me too bad, I could deal with the occasional downshifting and don't plan on towing a trailer too much, but it will see some trailer duty in the summer. What makes me think I'm down on power is the horrible fuel mileage. I'm guessing most 4.10 geared trucks out there are getting way better highway mileage than my 3.55 geared truck is.

As far as the code went, I was driving last night and got a CEL on the dash. Since I just bought the truck I've been driving around most of the time with my scanner attached and monitoring the live data, plus I've been keeping an eye out for any pending codes. As it happened I was just making a short trip so I didn't plug the scanner in when I left. Got across town and saw the CEL so I plugged the scanner in before I shut it off and it showed the P0420 cat code. I didn't clear the cat code until this morning just to see if it would clear on it's own which it didn't and after putting about 70 miles on today the code hasn't come back yet.

As far as the exhaust goes, I'm still planning what to do with it. No matter what route I take I'm not going to cobble it together. I haven't crawled under the truck yet, but being a 99, from what I've read the exhaust should be a 2 into the cat system, not the later Y pipe design so I need to keep looking to see what's out there. Duals would be nice, but then I'd have to fight with the single o2 sensor and decide which side to put it in.

 

If you do duals, you can use a X or H pipe, and put the o2 in the center. Although I've been told by a few on DF that it is no big deal to have it in just one side. It's not like it's a race motor.

 

Made some progress on the truck tonight. Checked down inside the throttle body and found some oil on the sides mainly of the intake, the floor was pretty clean and a bad pcv valve. Got a new pcv valve to hopefully stop some of the oil until I can get the plenum plate installed.

Checked #8 plug and it looked like new, but then so did the rest of them when I checked them so it doesn't tell me a whole lot without knowing how new the plugs are.

Sprayed some PB blaster on the o2 sensor to maybe start freeing it up so I can pull it out and see if it makes a difference.

But, the biggest improvement I think I made tonight was removing the giant mouse nest from under the air cleaner (on the fresh air side). That thing was packed pretty tight, then checked the inlet tube from the fender and inner fender which were both empty.

I unhooked the neg. battery cable while I checked the diff/tcase fluids and greased the front end which took about 15-20 minutes. When I started the truck I had all my radio presets, but the clock was reset so I'm not sure if I left it off long enough to reset the computer, any ideas? It's alot more responsive now and getting closer to where I would expect the power to be.

 

Trucks running better since I found the mouse nest. Had a light coat of oil on the sides of the intake, but the floor looks nice so I decided to replace the PCV valve while I was buying a new air filter. Then I was reading here that the parts house PCV valves are hit or miss so the next time I'm near a dealer I'll pick up a Mopar one. Planning on replacing the cat and now that the engine is flowing a little better, the stock muffler is sounding a little worse than I though so it's getting replaced too as soon as I decided on which ones to buy.


Got the build sheet today, not much I didn't know about the truck already, but I see there's an outstanding recall for the trailer hitch reinforcement and the hood latch that I need to get taken care of.

Also, does anyone know if a reman PCM for this truck would have the death flash in it? The PO replaced the PCM and the sticker is well worn, but doesn't look like a Mopar sticker so I was wondering if he used a parts house reman unit.

thanks

 

Maybe its been asked or mentioned and I missed it but does this truck have stock sized tires? The symptoms your describing sound like what would happen if you increased the tire size with the doggy EPA minded 3.55 gearing..
The generic atf+4 is fine..... It has to meet spec to have that label and atf+4 already surpasses the atf+3 the truck started out with from the factory...the dipstick says dextron (or was it merc?) is ok too but many say it will destroy the transmission fast especially if converted over from atf since it has different wear and friction properties... Of course many also say if the fluid is worn and dark replacing it will also mess up the tranny so there's a lot of opinions about what to do and not to do when it comes to those...

 

Sounds great about the ATF, Hopefully I'll have time to change the fluid this weekend. Had a bunch of test this week so I aven't had much time to get much work done, but luckily that means I haven't put many miles on it either.

The tires are a 285/75/16. I wasn't sure what it had from the factory, but the build sheet I got shows a 245/75/16 so there is one contributing factor. I was always happy with the older trucks I've had with 4:10's (but they were also 4 speeds which helped a little more) so it looks like I'll save up for a 4:10 swap.

I need to weight this truck vs the truck my brother just got, it's a 75 W100 with a 360/727 and 3.55 gears with 33x12.5's and a 2bbl and it just seems like his truck has more power than the 5.9 in mine.