Home of all dually trucks with the GMC/Chevy 3500HD series truck a point of interest.

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You can appreciate the “beef” of the GMC/Chevy 3500HD trucks, a stripped rolling 3500HD chassis weighs more than a running C1500!

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Welcome to the forum created October 2009

Recent Posts

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Body-Interior-Electrical / Re: factory electric fan issue / help
« Last post by ROAD on January 08, 2018, 12:38:10 PM »
   That fan is in place to keep the head pressure down in the ac compressor. And is controlled by the high pressure switch in the high side line on top of the ac compressor. unplug  the connector and jump the plug the  fan should come on if all relays and fuse are good.
Body-Interior-Electrical / Re: factory electric fan issue / help
« Last post by ED-NY on January 08, 2018, 12:15:34 PM »
According to my Engine Control Module Wiring Diagrams and Pin Identification manual you have an Auxiliary Fan Relay circuit:

#6 on the Black 24 pin connector, circuit #473  DK/BLU wire (see attached)

Body-Interior-Electrical / Re: factory electric fan issue / help
« Last post by ED-NY on January 08, 2018, 10:51:46 AM »
If you have the PCM service number ...might be able to locate a pcm pin out to see if it has a fan signal provision.
Suspension-Brakes-Hydraulics / Re: caliper assembly question
« Last post by remingtongoose77 on January 08, 2018, 09:58:21 AM »
thank you for the tip. I too did the sanding and lubricating.
Body-Interior-Electrical / Re: factory electric fan issue / help
« Last post by someotherguy on January 08, 2018, 09:47:51 AM »
That fan was original equipment on the 1996 C3500 dually that I pulled the 7.4 engine, harnesses, pcm, and many other parts from to convert my 1994 3500HD from diesel over to gas.

In 1996 it wouldn't be controlled by the pcm; pretty sure it's just a switch and relay arrangement, with the temperature sensor acting as the switch - though I never studied the wiring close enough to know for sure.  I believe it wasn't until the later 1990's before pcm control of the aux fan became a thing, and they eliminated that second temperature sensor over on the passenger side head.

Suspension-Brakes-Hydraulics / Re: steering alignment stuff
« Last post by ED-NY on January 08, 2018, 08:15:41 AM »
Any time I have axle questions I go to my local school bus garage, those folks work on them all of the time and have a high repair standard.

Did locate this motor home manual, front end I-beam specs are noted on page 3-2, might help some.

It appears GVW affects alignment specifications also.
Suspension-Brakes-Hydraulics / steering alignment stuff
« Last post by remingtongoose77 on January 07, 2018, 09:21:32 PM »
Hello all,

I have 96 HD. I bought it last May, tore it down the the frame and cab, then began the rebuilding process. I'm getting close to being done.

I just finished hanging both axles and all steering and suspension and I noticed something in the front end.

I rebuild my front axle completely, stripped it and powder coated it, rebuilt the front hubs and spindles. I put in new bushings, honed them to fit the pins and put it together.

I just set my front bearing clearance to the GM manual, I have them at .005 axial play. When the truck is on the lift and the hubs are facing straight and you look at them it looks like the hub face is cambered out positive. Is it supposed to be like this? I assume if it had a bunch of weight on it the front axle would flex slightly and make the tire straight.

Remember the truck is living on my 2 post lift. I normally see some positive camber in independent front suspension trucks. As the tires move up the camber in, but this is an I beam front axle, and I have no experience with it. I'm not too worried because its all in spec, but for the life of me I cannot remember what it looked like when I bought it.

thanks all. 
Body-Interior-Electrical / Re: factory electric fan issue / help
« Last post by remingtongoose77 on January 07, 2018, 09:12:53 PM »
Yes, my harness looks just like yours.

I sent my ECU off to be tuned by Ed Wright from his company "fast chip". He has been very helpful with questions that are computer / engine specific and he thought the electric fan was not an option in 1996. In addition when he tuned my computer he thought there was not a provision for an electric fan.

Thanks guys,

Off Topic Items-Politics-Jokes etc / Re: TBI tuning option!
« Last post by MrC. on January 05, 2018, 03:14:46 PM »
You are right Someotherguy, I did read that only 94-95 3500HD's had the high pressure pump. Thanks for stating that.

I have a 1994 3500hd. I have not checked the pressure, but from what I have read it should be 30psi with 42# injectors.
That said, would there be any gains if I switched to a 50-60# injectors and removed the cat and opened up the exhaust?

Off Topic Items-Politics-Jokes etc / Re: TBI tuning option!
« Last post by someotherguy on January 05, 2018, 09:01:26 AM »
I have been reading we (3500hd's) have a higher pressure regulator factory. I have read it is 30 psi as opposed to the 13-15 psi of a half ton truck. I have also read we have small stock injectors 42#
It's not a 3500HD thing.  The 1994-1995 7.4 engine has a higher pressure pump and different injectors than the earlier years, even in the 3500 and 2500 trucks.

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