I have really enjoyed the information shared here...I am a new owner of a 2500HD 4X4 Duramx LLY and have several questions:


1) I have put 285/75-16's on my truck and have noticed in several posts that there could be "issues"...what do I need to do to compensate or what should I simply be aware of??


2) I have noticed that several of you change oil and diff fluid at 500 miles...I currently have 1130 miles...should I be doing something even though the recommended service does not mention anything?


3) I am considering a K&N air filter...thoughts?


4) I too have the "morning chirp"...I am not worried about it, should I be?


5) I am considering a Cat back exhaust replacement...thoughts and recommendations?


I really appreciate the help and knowledge...thanks in advance!

Greg, I have 265's on my new truck. I didnt go any bigger for two reasons. 1st, the 285s will probably rub somewhere on the fender when turning, and 2nd, GM doesnt have the ability to reprogram the speedo/tranny for anything bigger than 265s. As for the fluid changes, I just got done doing mine. I have 2300 miles on my truck. There was a lot of metal on both front and rear diffs. I replaced the fluid with mobil 1 75w-90. I also did my 1st oil change putting in shell rotella t. I changed the fluid in the transfer case, and also put a new spin on filter on the tranny. I put a k&n air filter in my truck. Being the airbox has a big hole in it, I dont think it hurt any. As for the cat back, I just ordered a full turbo back system from Dynomax. I dont think you would see much improvement from a cat back because you still have a lot of twists and turns in the exhaust from the cat forward. Hope it helps ya out.

Emerick,


Thanks for the reply...since you cannot re-program for the 285's will it damage or hurt the tranny in any way?? I have gotten the rub issue addressed.


Did you do your fluid change at the dealer??

GregGil,


I also have the "morning chirp", doesn't seem to last long though. I have also noticed I have the dreaded "tick", only seems to be noticeable after driving for a long period of time. I have almost exactly the same mile as you (1141). I'm going to tow my old pickup (Toyota 4X4) up into the mountains and then I will do as "emerick115" did and change the fluids and Allison spin on. I was going to change the oil at 700mi but couldn't get the filter off(%^#^#&&)http://www.dieselplace.com/forum/smileys/Angry.gif So I guess I will have to go to the dealer and have them loosen it for me. I'm not really sold on the K&N but some seem to like it. Do a search and you'll see a lot of debate over air filters and their abiltiy to filter out dirt. I'm loving my truck I hope you are too

GregGil
Go to the parts store an get a tsrap filter tool, works like a charm on the filter.

1) I have put 285/75-16's on my truck and have noticed in several posts that there could be "issues"...what do I need to do to compensate or what should I simply be aware of??


The dealer can void your warrenty for oversize tires so I would be careful with them.


2) I have noticed that several of you change oil and diff fluid at 500 miles...I currently have 1130 miles...should I be doing something even though the recommended service does not mention anything?


Better safe then sorry later


3) I am considering a K&N air filter...thoughts?


I just run the stock paper and change it every 7500 miles


4) I too have the "morning chirp"...I am not worried about it, should I be?


Mine seems to come an go, the colder it is the worse it is. It's only belt noise from what I can tell.


5) I am considering a Cat back exhaust replacement...thoughts and recommendations?


I'm running the TTS catback and have dropped about 100* on the EGT and gain no sound level. It's as quite as stock in the cab with a nice mellow tone if you have the windows down. No drone's at any engine speed.


I really appreciate the help and knowledge...thanks in advance!

Diesel Tech,


Thanks for your input...a couple of follow on questions:


1) Can the 285's cause damage to tranny, etc.?


2) I looked at the tts website...who would you get to install the tts cat back and does it have warranty implications?

I have 285's on my 2004. The dealer put them on before I took the truck off the lot. They did not say anything about voiding the warranty with bigger tires. You would thnik that they would say you can only but on as large as 265's if it was going to void the warrant.


They had a truck there being delivered and it had 285's on it also. My wife said that that truck looked good with them bigger tires and that I should just have them dealer install them before I took it off the lot. She said the 245's made the truck look to wimpy.


I figure since the dealer put them on and it is documented on the sale, reciept they should honor any warranty problems if there ever was any. Many people on this site run 265's to 315's.


With 285's you should see a 4 to 4.5 mile an hour differance in on your speedometer. So going 60on your speedo you should be safe to say you are actually going 64mph.

Greg, the bigger tires shouldnt hurt your tranny any. As for installing the exhaust, if you are the least bit handy it should be a breeze. Most aftermarket exhausts all use the stock hanger brackets and all you need to do is unbolt from the square flange back and slide the new exhaust into place. Should be an easy job.