Thread: Tune-up for 3.8 Supercharged 2002 GTP

1. Pick any oil, I ran rotella and valvoline just about every oil change, they are normally the cheapest. I'd stay away from penzoil. since you live down south, you could run 10w30 if you wanted aswell.

2. I run napa filters, basically anything that is a wix filter works good.


3. Either Ac delco plugs or auotlite 606's, just remember that the 606's only last about 15k miles because they are copper cores.

4. Ac Delco wires are like 30 bucks off rockauto, to me they are the best wire for the car and cheap enough.

7. Trans fluid is Dexron 3 for that car, I wouldnt run anything else in it personally, you will need 7-8 quarts with a pan drop.


8. For anything else just check over small stuff. Perhaps replace the PCV, new fuel filter and check to see if teh intake gaskets and coolant have ever been changed.

Yea I forgot to mention that I planned to do a coolant flush and change. I forgot about PCV but yes that will need to be replaced. Where is the fuel filter loacted? Inline I assume?

I will eventually do a LIM and valve cover gasket change but cant do it right away.

Fuel filter is under car near rear driver wheel... You'll see it if ya get under there.

Id go Mobil1 and filter for a few oil changes at low mile intervals prior to sea foaming (crankcase) if that's what you plan to do. Coolant flush and replace with NON dextron coolant. Tranny pan drop, fluid change and filter is always great, i used the new dextron fluid, not aware of any issues doing so. Is it running well?

I like Taylor wires (8mm), but not necessary. Leave the coil packs alone unless problematic. You can check all you ground connections, battery and alt too, clean em up if they look bad. Plugs are always good thing. Check tires for uneven wear and if so, then alignment is called for. If new tires, might be reason why.

Check ROCKAUTO for stuff prior to going to Autozone, they have good deals at times.

LIM gasket? You have leaks showing?


Welcome aboard, good luck with new (old) car
post pics when you get the chance...

I would defintely do the standard, oil/filter, plugs/wires, air/fuel filters, and get a PCV filter for the supercharger (2 bolt plate on the charger covers it). I use Mobil1 10x30 syn, Delco filters, cheap plugs wires with NGK TR55 plugs, Delco fuel filter, and Spectre air filter. PCV was from Autozone, don't remember the brand.

Service the tranny, filter + 7/8 qts of Dex3 or Dex6, re-use the factory gasket if you can. Its designed to be re-usable, the crap gasket that usually comes with aftermarket kits are not, and they tend to leak. I use the Delco filter and fluid.

After these I would save and wait then change the LIM gaskets, valve cover gaskets, coolant elbows, S/C and T/B gaskets, new injector o-rings, and do a full coolant flush and re-fill (Dex or Green is up to you) at the same time. Make sure you get the metal LIM gaskets, not the standard plastic compound replacement ones.

Then you should be good to go on fluids, minus the P/S and Brake fluids but they should be ok.

As far as the GM Supercharger fluid goes tho.... (yes I'm about to go there again)
http://www.grandprixforums.net/remov...il-2-4906.html
Bottom of page 2 shows my bulletins from work (Parts Sales Rep @ GM Dealership) for use of Mobil1 5w30 in place of the GM S/C Fluid when fluid is not available. The dealership I work at, doesn't stock it, nor does any dealership within 100 miles. Its just not used enough to require us to stock it. So we have options. If you notice the bulletins, it states for the old M62 blower, but I have verified this still stands for use in the newer M90s, same gears, coupler, seals, bearings. Same fluid to be used between the 2 blowers, so if it can replace it in one charger, it can replace it in the other.
Should you wish to spend the +/-$20.00 for 2 bottles and have it locally, more power to you. If you have to order it and wait, you may consider this. Several including myself use it. I use a syringe and suck out the old oil every other oil change and replace with new 5x30 syn Mobil1. Blower runs fine. But up to you. just giving some options and opinions.

Coolone, Thanks. Everything looks pretty good under hood. I have not crwled under the car but just from the top view looks ok. Yes there is a little bit of oil under the SC snout but not much. There is some around valve covers. Eventually I want to get all the mail gaskets without having to go to the heads but all the top stuff. The tires are not worn uneven or anything. The tread is still pretty good but the sidewalls have cracks from rot. I got this car for my son who turns 16 next month. He has 2 more years of high school before going off to college so we have a little time to get things up to snuff and then it should last him for a long time. He wont be putting to many miles on it over the next 6 years but think this car is worth saving for a long time.

Originally Posted by coolone

Fuel filter is under car near rear driver wheel... You'll see it if ya get under there.

Id go Mobil1 and filter for a few oil changes at low mile intervals prior to sea foaming (crankcase) if that's what you plan to do. Coolant flush and replace with NON dextron coolant. Tranny pan drop, fluid change and filter is always great, i used the new dextron fluid, not aware of any issues doing so. Is it running well?

I like Taylor wires (8mm), but not necessary. Leave the coil packs alone unless problematic. You can check all you ground connections, battery and alt too, clean em up if they look bad. Plugs are always good thing. Check tires for uneven wear and if so, then alignment is called for. If new tires, might be reason why.

Check ROCKAUTO for stuff prior to going to Autozone, they have good deals at times.

LIM gasket? You have leaks showing?


Welcome aboard, good luck with new (old) car
post pics when you get the chance...

Thanks TL I didnt know where the PCV valve was exactly or the fuel filter. Do the NGK TR55 plugs have same heat range as the 606's and do they last longer than the 15k miles? Really thankful for the re-use tip on the tranny gasket. I was not aware that was even possible. I will check it for leaks and if non than I will re-use for sure. I will consider the use of Mobile 1 5w30 oil in the SC. I don't even know if the SC oil is available around here or not? Would Lucas help? Im all about saving money as long as Im not cutting costly corners. I love opinions and advice. I'm new to this car and want to do it justice as best as I can afford.My sons life could depend on it.

Originally Posted by TLSheff

I would defintely do the standard, oil/filter, plugs/wires, air/fuel filters, and get a PCV filter for the supercharger (2 bolt plate on the charger covers it). I use Mobil1 10x30 syn, Delco filters, cheap plugs wires with NGK TR55 plugs, Delco fuel filter, and Spectre air filter. PCV was from Autozone, don't remember the brand.

Service the tranny, filter + 7/8 qts of Dex3 or Dex6, re-use the factory gasket if you can. Its designed to be re-usable, the crap gasket that usually comes with aftermarket kits are not, and they tend to leak. I use the Delco filter and fluid.

After these I would save and wait then change the LIM gaskets, valve cover gaskets, coolant elbows, S/C and T/B gaskets, new injector o-rings, and do a full coolant flush and re-fill (Dex or Green is up to you) at the same time. Make sure you get the metal LIM gaskets, not the standard plastic compound replacement ones.

Then you should be good to go on fluids, minus the P/S and Brake fluids but they should be ok.

As far as the GM Supercharger fluid goes tho.... (yes I'm about to go there again)
http://www.grandprixforums.net/remov...il-2-4906.html
Bottom of page 2 shows my bulletins from work (Parts Sales Rep @ GM Dealership) for use of Mobil1 5w30 in place of the GM S/C Fluid when fluid is not available. The dealership I work at, doesn't stock it, nor does any dealership within 100 miles. Its just not used enough to require us to stock it. So we have options. If you notice the bulletins, it states for the old M62 blower, but I have verified this still stands for use in the newer M90s, same gears, coupler, seals, bearings. Same fluid to be used between the 2 blowers, so if it can replace it in one charger, it can replace it in the other.
Should you wish to spend the +/-$20.00 for 2 bottles and have it locally, more power to you. If you have to order it and wait, you may consider this. Several including myself use it. I use a syringe and suck out the old oil every other oil change and replace with new 5x30 syn Mobil1. Blower runs fine. But up to you. just giving some options and opinions.

Originally Posted by falcongt

Thanks TL I didnt know where the PCV valve was exactly or the fuel filter. Do the NGK TR55 plugs have same heat range as the 606's and do they last longer than the 15k miles? Really thankful for the re-use tip on the tranny gasket. I was not aware that was even possible. I will check it for leaks and if non than I will re-use for sure. I will consider the use of Mobile 1 5w30 oil in the SC. I don't even know if the SC oil is available around here or not? Would Lucas help? Im all about saving money as long as Im not cutting costly corners. I love opinions and advice. I'm new to this car and want to do it justice as best as I can afford.My sons life could depend on it.

The NGK TR55s are 1 heat range colder than stock, but they are iridiums like the factory plugs so they burn hotter than a standard copper core and last alot longer, but they run about the same price as a standard iriduim plug (+/- $10.00 each i think).

The GM Supercharger oil is GM# 12345982. Call to a local GM Dealership and have them check the number, alot of dealers have a locator so if they don't have it, they can see which dealer close keeps it in stock. If like at the one I work at, and 100 miles is too far to drive for oil, use the Mobil1 5w30. Do not add lucas to it. Just the synthetic oil and change every 5-10k.

Would a coupler change be a good idea (unsure of mileage unless I missd it)? I probably would not do it oil the standard tune up stuff, but when you have the supercharger off for the LIM gaskets it might be a good idea to change. Other then that I see everything else has been touched on.

Coupler change? What coupler? Mileage is 132k + some change

Originally Posted by dbextreme

Would a coupler change be a good idea (unsure of mileage unless I missd it)? I probably would not do it oil the standard tune up stuff, but when you have the supercharger off for the LIM gaskets it might be a good idea to change. Other then that I see everything else has been touched on.

No comments on this section?

Originally Posted by falcongt

I know this is not part of a regular tune up but thought I would throw this in as well. This thing rides pretty rough (bad dry rotted tires) and seems to bottom out. Once we get the new tires on it I plan to re-evaluate the ride but suspect it will need new struts. I find them at Rockauto from $50-$100 bucks some with springs and some with coils. Any recommendations on this?

Also is there any other problem areas with from suspension? Any particular rubber components that normally need to be replaced? Car has 132K. I felt something in the floorboard when hitting a big bump like something was hitting against the bottom of the car or frame. Any suggestions as to what this could be?

Maybe an exhaust hanger is gone and the piping is hitting the bottem side of the car.

As for the suspension, if the car does bottom out then likely it will need new struts. You have the option of buying a quick strut or just buying a strut and putting the old coil spring on it with a new strut mount.

The coupler is the piece that "mates" your snout of your blower to the case (If I explained that right). It's a round plastic piece. If you google it there's pics for a better visual.

INTENSE-Racing.com: INTENSE Supercharger Coupler Change Kit

Oh yea I remember seeing that in a few post that I have read. Don't know anything about superchargers so I hadn't thought anything about the coupler. Do they get worn out and wobbly or something like that? If its a piece that is prone to wearing out and needing to be replaced around a certain mileage or as a precaution like a timing belt or chain would be then yes that is something I might look into replacing. Thank you for the heads up.

Originally Posted by dbextreme

The coupler is the piece that "mates" your snout of your blower to the case (If I explained that right). It's a round plastic piece. If you google it there's pics for a better visual.

INTENSE-Racing.com: INTENSE Supercharger Coupler Change Kit

I'm pretty sure that we will need to replace struts. Will determine more after new tires. Like I said before I haven't looked under the car yet so I really don't know how the engine is mounted or anything. I was thinking that it felt like the cradle or what ever you call it might have been moving and causing something to bind or it may just be the front suspension bottoming out? I'm not a suspension expert by any means so I might just take it to someone who knows those things more and have the whole front suspension checked out. Hopefully it isn't anything too major.

Originally Posted by Fivefingerdeathpunch

Maybe an exhaust hanger is gone and the piping is hitting the bottem side of the car.

As for the suspension, if the car does bottom out then likely it will need new struts. You have the option of buying a quick strut or just buying a strut and putting the old coil spring on it with a new strut mount.

Originally Posted by falcongt

Oh yea I remember seeing that in a few post that I have read. Don't know anything about superchargers so I hadn't thought anything about the coupler. Do they get worn out and wobbly or something like that? If its a piece that is prone to wearing out and needing to be replaced around a certain mileage or as a precaution like a timing belt or chain would be then yes that is something I might look into replacing. Thank you for the heads up.

The coupler will wear out, just depends on how the car is driven and how often the fuild was changed as to how long it will last. If you are constantly snapping the throttle it will wear out faster than just easy sunday driving. Most tend to start making a rattle around 100k+. Fairly easy to change out with basic tools. Simple writeup here. VVV
How to replace an M90 snout coupler without removing the entire blower

You can get a coupler from several vendors. GM is not one of them, GM services the Charger as a whole unit, no couplers. ZZP, Intense, Ebay, etc... my favorite is ... INTENSE-Racing.com: INTENSE Supercharger Coupler Change Kit - Gets you a new coupler, new fluid, and the gasket maker stuff. $40 + shipping.

If there is no noise (usually sounds like rocks in the blower, or a sack of marbles being shaken) you are likely still in good shape, but you could still change it if you like. What happens is the 6 holes get egg-shaped due to torque and the slack causes a rattle. Its more annoying than anything, it won't hinder the blower unless it actually breaks and come apart, but that NEVER happens.

When I did mine, I followed the write-up I linked above, but I saved a few steps. I thought, I'm not unbolting my Alternator, I can work around it. So I did. Left the 1 bolt that requires the Alternator to be moved still bolted in, but backed way out, and just flipped the snout over, like so...


Made it a little harder to clean out everything with a rag, but I got 99% of it so I didn't worry.

Word of advice tho, WEAR GLOVES!!! thick ones! The old fluid is nasty smelling, you want a good idea, open the check/bolt and get a smell. It will soak into your hands and stay for a couple days, not ideal if you like touching your woman. so wear good latex gloves when doing this.
And lots of rags to soak up the fluid. It will go everywhere.

Took me about 30-45 minutes to change, wasn't hard at all.

EDIT: be careful of the vacuum Tee connecting into the lower intake manifold. You can see it in the picture at the bottom between the white rags. The lines are plastic type and can break if your not careful with them, that will cause problems and easy to over look.

Thanks TL. Very helpful. I figured the noise would come from rounding out the holes but wasn't for shure if that was the main concern or if it was prone to gernading. The engine is very quiet. I really don't think the car has been beat up too bad just a little neglected. Once I get the oil changed I will listen more closely to see if I hear any rattle from the SC. Does reving up the engine a little make a difference in checking the SC for noise? If no sound is coming from it I may wait till I do the LIM and stuff to replace the coupler.

The only real way to test the coupler is simple. Take the belt off and rock the pulley back and forth, if there is slack it needs to be replaced. If its tight, then you're still good.

Check the video.


This is my personal video for the supercharger on my car, soon to be fixed... again. Cheap Ebay ones are cheap... buying a good ZZP or Intense one this next time. The rocking you see is not moving the gears or rotors at all, that is complete slack in the coupler. Amazingly aweful.

Funny note too, in the garage, the simple tick was loud on camera, tho was also a 1/2 sec behind the video too

As for suspension, KYB makes quick struts, about $120 per piece @ Rockauto. I can dig up the part #'s if you want as I remember they don't just list it for the 97-03 but they're there... good price considering it only takes 5 bolts and the entire strut, spring, strut mount combo is replaced. No need for spring compressors, no putting nice new struts in worn mounts then wondering why the suck! Lol... It's a worthy investment.