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GMC Jimmy Performance Mods

vivalabamvivalabam Member Posts: 4
edited March 2014 in GMC
I really need help with this one. I'm trying to get more speed out of my '99 Jimmy, but the problem is I don't know what I can and cant do because of the internal computer. I know I can use a power programer but I'm not sure what kind. I also want to put in a cold air intake but the stock intake looks likes its two parts with a sensor in between the two parts. I don't know what to do with that sensor if I put in a AEM brute force cold air intake. My last concern is the muffler. I know that a straight pipe would ruin the computer so I was thinking about putting in a flowmaster performance muffler but I don't know if that will mess up the computer too. If anyone could help me out or give me advice on something else I can do to get the most out of my Jimmy (besides a supercharger) I could really use the help.


  • repairdogrepairdog Member Posts: 948
    Have to have that MAF and temp sensor in the intake to feed the ECM. Likewise with the O2 sensors before and after the cat or it may have some mixture problems and the SES light will stay on. You can just add a K&N into the existing housing but watch over oiling as it gets on the MAF and screws up the readings and gas mileage. You can add a turbo muffler but it still sounds like a V6 and not smooth like you probably want (did it and took it off - interior noise was bad). They have a $400 high perf MAF that helps some but its 190-200hp so can only do so much. If 4wd that drivetrain steals (transfer case and front diff) lots of power also. Good luck - buy a V8 but then 13mpg city.
  • vivalabamvivalabam Member Posts: 4
    So your saying that I can't put a AEM bute force cold air intake? If the O2 sensors are only before and after the cat I shold be able to do anything to the muffler right? Even straight pipe it.
  • repairdogrepairdog Member Posts: 948
    Search on your topic cause there are several performance sites to answer specifics but you do need the MAF and temp sensor to run and as for no muffler and no back pressure would guess the O2 sensor will be off and your next door neighbors will certainly love you. You do not gain much from these mods like 5 hp and may not even notice it but thats only my opinion vs the possible SES light triggers.
  • vivalabamvivalabam Member Posts: 4
    yeah I know you don't get much with a muffler mod, I just want that deep loud tone, right now its too quiet. Thanks for the help.
  • mobiusdieselmobiusdiesel Member Posts: 5
    Need help finding a good set of wheels for my Jim. Still have original 15X7 Rims, would like the five spoke 16X8 2002-present GMC Sonoma SS Rims which have the same bolt pattern as my 15's, but I can't seem to find any information about wheel offset, hub chamfer measurements for fitting them on my Jim. Any Ideas? Web-sites I can get measurements? Or even better, do you guys have any? This is the aftermarket part #ALY05116U10
    OEM #ALY05153U20
  • blaze4x4blaze4x4 Member Posts: 29
    I purchased 16x8 Centerlines Mohave. Your bolt pattern is the same as a Camaro, Firebird, etc. it's five on four and three quarters, thats 5 lugs, with 4 3/4" distance across lugs (center to center). As for back space, depending on the size tire, (I used 265/75R16) you need a minimum of 5". Thats the measurement from the rim mounting surface to the back lip. That will put the tire inside the wheel well and not put excessive strain on the wheelbearings. This was installed on my 2001 4DR 4WD Blazer with a 5" BDS suspension lift. You'll probably only be able to get a 245/75R16 tire, without lifting your Jimmy. Hope that helps!
  • mobiusdieselmobiusdiesel Member Posts: 5
    Thanks that does help... I can't seem to find any information for the wheels on the newer S-10 and Sonoma pickups though. I really like the syle and to have original GMC badging on the wheels would be a huge bonus. See my Jim is lowered 3" front and rear and converted to 2wd. If I had a 5" lift on my Jim the Mohave wheels would definitely be a good buy but... well you know.
  • suiteridesuiteride Member Posts: 1
    I would like to know the largest tires i can get for my stock 99 Jimmy 4wD. Its an SLE. I hope this is the right forum for the question but I couldn't find a better one. As a snowboarder I drive to the mountains often. But in the summer I like to 4x. I'm not quite ready for a life (misspell, but true anyway) Lift yet but would like bigger tires. Any advice would be much appreciated.
  • repairdogrepairdog Member Posts: 948
    Per seeing other posts in several forums and owning 4 of these - afraid the 235-75R15 is it (235-70 is alittle wider but alittle shorter and not as common used on 2wds). With a 2" body lift from Performance (unbolt the body from frame and 16 bigger spacer inserted) you can get 30-31s on without rubbing if properly inflated. Now chains will always be a problem if not a really good fit at max turning. Then theres the Superlift 6" suspension kit thats allows even bigger but handling at higher speeds with the high center of balance will be bad. With bigger tires your gearing will be off so if you have the standard 3.42 slower acceleration and speedo reads low.
    A big problem on this model is how low it sits and the cast oil pan and trans pan are exposed - gas tank too. GM has skid plates for these and there is a Slam guard pan for the trans that has a pan with skid plate and drain included.
This discussion has been closed.