Track down cause of abnormal slowness.. (1 Viewer)

[desertwampa]

I realize that the data is probably all over the place, and there's LOTS of variables..but since you all are the likely most experienced folks with the 80..I figured it can't hurt to ask. The question is below, but I'll say after posting on FB most people seem to say that my results (72mph) are NOT normal. Can you guys list out some likely culprits
rig is 97 lx450. gas. fze

On the freeway today, floored the gas pedal. Couldn't go faster than maybe 72mph. Pretty flat road. 35" Heavy mud terrains, 3" lift and stock gears. What is your top speed in miles per hour? Just trying to guage what's "normal". thanks

 

[devo]

90+ mph

 

[SpenserAK]

Same tire size/lift/gears. I could easily go faster than that, and don't believe I've ever come close to maxing out the pedal. Sounds like something is funky. Maintenance history?

 

[ajax1]

Clogged cat or muffler
95 stock gears in mtns I 70 I can do 70 to 90 of course it depends on hills, 285 75 on 17s Arb bumper 2.5 lift and roof rack
96 5.29: 37s full armor, storage box and 37 spare on bumper, 4 inch lift. 70 to 90 mph
Both trucks are equal in acceleration , I also kick out of over drive before any hill.
I did set the cruise on 80mph in the 96 from Vail down to Junction and it held it pretty good only needing to kick out of cruise and overdrive to maintain speed.
Not knowing the health of your truck hard to say what problem is, did it just start are always been this way? Any codes?

 

[fourtrax]

90+ easy , a stuck brake caliber could make it slow.

 

[jpoole]

It won't change the overall story much but is the speed from an uncorrected speedometer or GPS, ie. how accurate are your numbers?

 

[desertwampa]

Same tire size/lift/gears. I could easily go faster than that, and don't believe I've ever come close to maxing out the pedal. Sounds like something is funky. Maintenance history?

not alot to go on. Reading through things, I guess an easy place to start would be to have my exhaust system looked at

 

[desertwampa]

Clogged cat or muffler
95 stock gears in mtns I 70 I can do 70 to 90 of course it depends on hills, 285 75 on 17s Arb bumper 2.5 lift and roof rack
96 5.29: 37s full armor, storage box and 37 spare on bumper, 4 inch lift. 70 to 90 mph
Both trucks are equal in acceleration , I also kick out of over drive before any hill.
I did set the cruise on 80mph in the 96 from Vail down to Junction and it held it pretty good only needing to kick out of cruise and overdrive to maintain speed.
Not knowing the health of your truck hard to say what problem is, did it just start are always been this way? Any codes?

no codes. and it's been pretty slow since I've owned it, but haven't really pushed it before that day. Gonna get the cats/exhaust looked at

 

[desertwampa]

no codes. and it's been pretty slow since I've owned it, but haven't really pushed it before that day. Gonna get the cats/exhaust looked at

actually, it did have the egr 0401, but I threw in the resistor bypass.

 

[fourtrax]

Might do a compression check. You can usually get a loaner gauge from the ocal box store.

 

[mudgudgeon]

What is your top speed in miles per hour?

How long is the downward slope? And is there a run up before the down slope?

 

[lumbee1]

Get a cheap IR thermometer and measure before and after the cat.

I can go 90+ but I'm rebuilt with a supercharger.

When you say floored at 72mph, what is your RPM? Do you have a scangauge? Is the truck struggling to maintain 72? Do you hear any strange noises?

 

[fatrap]

1. Tune up?
2. Fuel filter (yep) ?
3. Like Ajax1 said above, cat converter may be plugged.

My 80 has stock tires and I can hit 90 real easy.

 

[Mark W]

Top speed? more than I ever really want to push it to. How fast have I gone? 85-90 with more left.

You are gonna have to give us more than that. ANYTHING that reduces power or increases load or interferes with delivery of power to the load can result in an inability to reach higher speeds. With no more info than what you have given, nothing can be ruled out and nothing comes to the fore. Any suggestions you have gotten or will get are nothing more than wild ass guesses based on... well based on the nothing you have given anyone to work with.

I could throw out 40dozen "it could be" thoughts but why waste that time. For all we know it is gonna turn out that you have two dead cylinders, you are smoking like a mosquito fogger, you tire pressure is at 5psi and you have a 20x20 canvas sail mounted on the rig for some reason.

Give info!

Mark...

 

[simple]

"posting on FB"

Well that's one problem worth solving.

 

[bigredmachine]

so i think that we still didnt get an answer if that 72mph is what the speedo is reading or corrected, not saying thats that easy answer to the problem but still kinda good to know before we just start guessing

 

[ppc]

If real top speed is 90 and the speedo shows 72 that is a 20 percent difference. That is is much greater than any ratio of gear sets available in the market when combined with a 35 inch tire.

@bigredmachine if the speedo was that far off and you were doing 90 you'd feel no need to complain about slow performance. You'd be to busy clinching that steering with fear.

 

[leonard_nemoy]

I'm lucky to hit 80mph anywhere I drive...... what no one is mentioning or asking is where are you driving. I am sure I could go much faster if the interstates I was driving on were flat. But everything in utah pretty much has some sort of grade.

Are you struggling on flat roads or roads with grade?

Also, are you locking it into 2nd gear to
check your top speed or just cruising in drive.

 

[SpenserAK]

It won't change the overall story much but is the speed from an uncorrected speedometer or GPS, ie. how accurate are your numbers?

With 35s & stock gears, my speedo was about 11% off when I corrected it with a yellr box - same result if you calculate stock 275/70 & 315/75. Assuming it'll be roughly the same, that makes his 72mph about 80. Not nothing, but not a ton. I think a healthy 80 should still be able to go faster, but does it need to...

 

[ppc]

Weight will be a big factor as well.