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    The only "Shire" in the USA !
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    Formula Firebirds, Old GM ( EMC and EMD)2 stroke diesel trains
  • Drives
    GMC 2500HD Firebird Formula 455

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Formulabruce's Achievements


Enthusiast (6/11)



  1. This is 100% correct. At one point, I used to swap out my T stat for the summer to a 160, which worked perfect and the ac ran cooler, but after some research and testing I found my truck doesnt get above 195 unless towing. I would HIGHLY recommend a upgrade size trans cooler if you tow, the stock ones seem to be bare minimum IMHO.
  2. 05 is same as 04, same as 06, and 07 classic in 3/4 ton , 1 ton only.
  3. There are a FEW "Black bear" tunes. They are VERY NON descriptive on what they are, and do. I will guess they only adjusted the trans shift points. Then messed with engine timing, mixture etc. NO tune will disable the 1-2 rpm up shift. Even a Brand new GMC Denali will NOT downshift to 1st when the cruise is on going down hill. ( decent control) . I am betting youll be doing a trans rebuild if you start to manually shift it if its got over 150K on it. Your 4 crew cab is Not a light truck.
  4. Jay, 1. The Power you seek DOES come from a slow blow fuse. It is under the hood, DS in the big plastic Distribution box. It will be "MISSING". Its Square and closer to the engine. This will power up that +12 v pin at the 7 pin connector. I do not recall what its called, but its pretty obvious. 2. The reverse camera. IF your camera is "wireless" ( only has ground and hot from reverse light AND an antenna) You will NOT want it powered all the time. Why? There are folks driving around with more powerful transmitters and you will Receive THEIR feed. I drove 50 miles one day on a busy highway and all I saw was the INSIDE of a Horsetrailer that was near me on the road. This is for WIRELESS only... Wired, No issues.
  5. Adding a capacitor ( noise suppressor) is an old trick that used to work well, and may just fix this. ( credit to Pizza) The Body control module ( all cab functions) GROUND is UNDER the truck, on the DS, right under the DS door on the CAB mount Extension facing the REAR of the truck. These ground wires need to be removed and cleaned well, and frame cleaned. After put some waterproof GREASE on it.. Did you do this ground?
  6. My vote get some THROTTLE BODY Cleaner ( ONLY use specific Throttle body cleaner) pull off the air intake giant hose clamp, and hose, and clean, clean, clean, and back side of the throttle plate too. All it takes is a Little dirt to cause this.
  7. The problem lies with whats called a Ground loop. The radio, for lack of a better term, is using the speakers as a ground. Pull the radio. If you used an adapter pigtail, make sure you Solder the power and ground leads. Check the ground wire size, make sure its same as power. Check the ground wire ( truck off, key out) coming to the radio, to truck ground with a ohm meter. I turn on the beep on my meter, so I don't have to look at the resistance. Probably a NEW ground wire from the chassis of the radio, to a GOOD truck ground, ( possibly one of the 2 cigar /12 volt outlets below) will do the trick. Good luck!
  8. BCM Ground. Driver side CAB Extension mount ( just under the DS door) On the mount, facing rear are a bunch of wires grounded to the mount. Remove, clean WELL, then grease/woolwax after re installing. Cost... about Free... Still have issues? Grounds at back of engine to Firewall..
  9. I only use Dex 3 compatible, and ALWAYS re use the original Rubber pan gasket on the 4L80E. the aftermarket gaskets are folded paper. ter originals are rubber with metal inside and very durable. Im not sure the 1/2 ton HD gets a 4L80 though...
  10. Get a good used 6L90. You'll need a harness and a controller to run the 4l80, and the link to the current truck harness will not match. Even making the 4L80 a manual shifting trans will still cost more and then youll still need a lock up connection. Call these guys. The 6L90 IS actually a more rugged transmission. whats wrong with it? https://www.justchevytrucks.com/
  11. So, did you do the grounds on the frame extension below the drivers side door, facing the rear of the truck? If not, better get those wires and frame clean, and cover it with marine grease after.
  12. Check the grounds on the brakes. some controllers are more sensitive. The grounds are usually a metal magnetic disc that moves and tightens the arms/shoes. These, and the area they ride on can get rustly
  13. DOT 4.5 is THE Highest you can go. It has a slightly higher boiling point, still synthetic.
  14. When replacing, I use "Copper" Never size to add a 3rd dissimilar metal between the threads. I get no corrosion of any type. There are brackets to hold the manifold tight on the DS rear if you want a quick fix, but it bolts to the back of the head.
  15. Does this have a 2500 HD cooling set up, or is it the 1/2 ton electric? Clutch on fan can cause this if the 2500 type. time for pics and more facts
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