No dude i ment that as in all do respect... LOL.. how my truck performs from 3.55 to a 4.56 .. So far all i can say is WOW !!!! pulls strong real strong going up hills stays right in OD. now i havent hit my 500 mile yet for the break in its a hole different beast , im just barley touching the throttle and she just pulls. she will put you back in the seat some its like running with stock tires only better.... i wish i could of went from 3.55 to a 4.10 then a 4.56 to give ya a better idea.. around town i can punch it a little and she will fly ... but i need to break em in for awhile then ill give ya a better update.. like i said there is only 300 rpm difference from a 4.56 to a 4.88 how much driving on the highway will you do ??? like 95% country/city driving ? 5 % highway ?? give you another idea , im off the gas then on it , the only down side i see is if you go with a smaller tire then you mite have to much gear , be a hell of a TQer !!! ... i still need my speedo fix to tell you about the shift points.... no more of the truck being a dog at 45 mph in OD at 1600 rpm , like it use to drop in at 1100 rpm..

 

Silver, I have a '95 5.9 auto 35's and 4.56 gears. If you stay with 35's, I think you'll be happier with the 4.56 gears. I was on the fence too before I got mine and can say I don't regret them at all. It really puts you back to stock on the highway. If you're not going to keep 35's on it, then you might want to stay with your 4.10s. But, if you're going to go bigger than 35's, I'd say go up. I think the 4.56 gear is a perfect match for 35's on my truck. I drive it around town and on the highway. I was going to try to get you your RPM numbers today but, since it's snowing, I don't know that the numbers would be the same.

 

My biggest question has been going with 4.56 or 4.88. I really prefer to stay with 35's, but only if I can get reasonable performance out of it. I'm leaning more toward 4.56 right now because if I ever take my lift from 6" back down to 3" (I hope not to, but you never know), I could still run a 295 or some other tire that is closer to 34" that would work with the 3" lift, but not be too small for 4.56. If I go 4.88, i'm really stuck with running at least 35's.

I will know for sure when I install the tach this week. Most of my questions can be answered just by knowing what RPM I am at, and where I need to be. The only reason I think 4.88's are an option at all are because of this dang overdrive auto trans. If I had a manual trans, there would be no question, i'd definetly be getting 4.56.

 

I put the 4.56's in mine with 35's and it was great. O/D works normal, pulls the trailer better, better overall drivability. Awesome to drive again. The 37's I have now were onthe rearfor a few months before I took the truck apart to put the new lift on and it did fine with the 37's also. The RPMs were a couple of hundred higher than when the truck was stock and if doinga lot ofhighway or over 60-65 driving would recomend the 4.56'sover the 4.88's

My 2 cents....

 

Silver, I wrote down RPMs on I-25 this morning. Keep in mind that this is with my 305/70/16 tires that I use in the winter and not my 35's that I use in the summer.
OD On...
30 mph - 1250 rpm
45 - 1500
55 - 2000
65 - 2250
75 - 2500
I hope that helps.

 

Thanks Aubrey, I appreciate it. I'll be installing my tach tonight.

 

Running 35's and 4.56's in my 98 318 truck. It pulls well, but honestly would rather have the 4.11's. Well, at least part of me. I like the way it pulls around town, but I do quite a bit of highway driving, and pulling much speed at all the revs get kinda high. Especially up here being as cold as it is (north of 55'th) I spend quite a bit of time with the computer locking out O/D. Long drives (700mi) in 3rd with 4.56's sucks ***. AND gas. If you're ever considering going to smaller tires again, and are likely not to go bigger than 35's, and do ANY extended highway driving, i'd recommend the 4.11's.

 

That's actually been one of my concerns. Right now, I can get away with driving around in 3rd because with the 4.10's, the RPM's are not too bad. OD that is about useless for anything other then perfectly flat driving over speeds of about 65 or 70. With 4.56, if power in overdrive isn't better, then driving around in 3rd will be worse then it is today because of the higher RPM's. This is a worse scenario then I am in today I think. This is one reason why 4.88's were an option. My hope is that they would put me at a high enough rpm that OD would be useful again at speeds around 55-65.

 

I wonder if I could have my PCM flashed so that it doesn't go into overdrive until a higher RPM/speed then it does today. That would actually make the 4.10's a little better.

 

Have you tried adjusting the shift cable at the TB? There is a lot of change that can be made with simply adjusting this cable. Be careful though. If you have recently reset the PCM and you do this, you might just get a big surprise when you try WOT. I did this while playing around with my new programmer and my tranny didn't know what to do so it just dropped out of gear, or just down to 1st at around 40mph, and my rpms instantly jumped up to 6,000+ (the tach was tapped) and about scared the crap outta me!!! I immediately let off the throttle, let the tranny kick back in and everything was fine but I learned that you have to let the PCM learn the fuel adaptives for a while BEFORE adjusting that cable!!!

At any rate, adjusting the cable does make a huge difference with very small adjustments to positioning. Moving it foreward causes the tranny to up-shift sooner, causing the bogging down in overdrive at slower speeds. Moving the cable toward the firewall will cause the up-shifting to happen later, and will downshift sooner, thus helping the truck to stay more within the rpm ranges you are seeking.

And by the way, I am running the 4.56 gears with 36.5" tires. I believe that my rpms at 70mph in OD are at about 2,200rpm. I will check the various rpms when I leave here in a bit and will post later what they are.