I started posting this as a reply to an old R&P thread in Drivetrain - but really the issue is beyond that - so here goes:

I can't maintain freway speed (70-75mph) without my auto tranny constantly downshifting and unlocking the torque converter with these heavy 32" tires on steelies. I tried with the stock wheels/tires and it's really not a whole lot better. This truck is just a MAJOR dog and it's starting to get to me.

I pretty much have to leave the overdrive off and run at 4000rpm all the time on the freeway to be able to maintain speed up and down hills - which I don't like (I drove all the way back from Arizona this way... )

Maybe something is wrong with my engine that has reduced its power output...

I have been intending to regear the axles to 5.14's to help - but now that I think about it some more, since 5.14 is ~10% higher than 4.6 that'll only bump the RPMs up to maybe 2-300 (if my math is right)... I don't think that's enough to make a difference.

Anyone else have this problem with their auto tranny? It drives me mad. Maybe I'll buy some 25" tires for the street

Is there a simple way (I guess I could arrange a dyno) to tell if your motor is putting out the correct amount of power?

I put on a Calmini exhaust and a K&N drop in.... no significant difference. I corrected the timing... turns out it was advanced 5 degrees too far - but that didn't help (retarding the timing should have, in fact, reduced power... but I thought since the computer and fuel map are set up for 15 that it might help).

What's the best way to go here? I guess I need to establish whether there is an engine problem or not... and then decide what the best way to get more power is.

Then again, SLR has performance cams for $475... maybe I should go that route (how bad an install is that? I could probably do it - but I don't want to get myself in TOO deep.)

I don't think re-gearing is worth it with anything less than 5.88's or so, at least for me and my 33's.

I have 4.6 diffs now, and in hilly terrain, I also have to down shift (5 spd) to maintain speed uphill.

My truck is about 5,200 lbs with normal gear on board, more if loaded with extra tools or parts, etc...(Or god forbid, passengers...)

The 1,000 lbs of stuff (Steel, etc) added to improve survivablity on the trail is not great on the highway.

I look at it this way...I just go slower up hills, and coast up again on the down hills...and I pretend I'm being paid the cost of new gears to let the truck slow on the uphills.

Glen, I feel for you but I think you are too used to the sc2000

I too would appreciate any suggestions... but as TJ stated we both have HEAVY trucks and may have to just deal with it

I sent a PM to Keith asking what he thought of the SLR cams and if he'd help me with the install... They're supposedly good for ~20hp.

With my 32s, about the only thing I really noticed after switching from the stock 4.636 gears to 4.90 gears is that I am able to stay in lockup more/longer on hills and such. I'm still acutely aware of when the converter unlocks and I turn the overdrive off accordingly, but even before I changed gears I wouldn't say I found myself having to run with the overdrive off more than on an as-needed basis. Climbing up a mountain or such is the only time I recall ever having to leave it off for an extended period.

Yeah, but the 10% difference is the same as the jump from stock 30" tires to 33" tires. So in essense, you'd be getting a shorter gear ratio than an equivalent stock Xterra...

That 10% makes a HUGE difference.

That being said, my truck (33's) was a dog w/ the stock 4.636 gears. But since I've put on headers, I don't have the constant OD annoyance that I used to. Even when towing my popup, only the big hills causes me to drop it out of OD.

I don't think adding cams w/o doing anything w/ the intake/exhaust is going to do much for you. Calmini's exhaust isn't a true cat-back, and the K&N drop-in filter is only giving you the ability to save $$, but not really doing anything for performance. Get the external upgrades done, first, then worry about internals.

Knew I shoulda just done the SLR headers rather than putting on new stock ones.... I probably would have failed inspection with 'em, though because I have an '00 Federal model (i.e. the only cats that I have are the ones that SLR removes - so I'd have NO cats).

They are a bit of a dog. I only have 31" ATs, but I do have sliders, full skids, and shrock bumper so the vehicle is heavy. I also live at 5,000' which doesn't help either. Even driving on relatively flat roads I do have to turn off OD on pretty much any slight incline. When I hear the torque converter unlock, I just take it out of OD. It is a bit of a PITA.

Edited to add I have the Calmini exhaust and K&N FIPK which did definitely help when I added them several years ago

So you do have the cats still? Maybe that is the problem. Those things get clogged up after awhile and you lose power.

When we went to Moab a few weeks ago from Florida, I was having the same issue and made our group aware of it. Around 68-70 on even the slightest of grades the engine didn't have enough power to get up without turning off the overdrive. I found the sweet spot on the way home from Moab at around 78mph on gps not on the gauge. Back here at home i'm not having any issues at all, it was just on the long grades on the trip. I didn't use cruise control at all (I've never liked how it floors it to maintain speed) and i'm running 32's also.