97 Suburban front diff replacement

Discussion in 'GMC Truck Forum' started by scavanger, Jan 1, 2011.

  1. scavanger

    scavanger Full Member

    May 15, 2007
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    machinest working on retireing come June 2015
    My brothers 97 suburban was making lots of bad noises in the front diff. About a yr ago his rear axles came out going down the road taking reverse out of the transmission . Don't know if this had anything to do with the little stub shaft with splines and gear on it in the front axle breaking but he had to replace that also at that time. We think there may have been a chip from the shaft stayed in the diff and did some damage. The pinion had a couple corners broken off which we think went through the ring and pinion, and partly destroyed the bearing cage on the pinion bearing. Looked pretty rough in there with some gouges in the case. The pinion actually turned hard.

    We found a diff at a salvage yard for $200, took the old one out and find out that the replacement didn't have the switch in it to prove that it was in gear. The switch on the 97 original is next to the actuator on the passenger side extension shaft. We studied the situation and considered modifying the wiring but decide that we could switch the extension shaft housing . Everything is the same except the switch and the length of the casting where the actuator screws in. We disassembled the extension shaft on the shelled out diff , cleaned and inspected. Everything appeared to be good so we did the switch. We did have to use the 3/4 in long plug that comes with the conversion from the heat actuator to the motor type. This suburban apparently had been converted.

    Everything worked the way it should. :D

    To get the diff out and back in we had to turn the front wheels far to the left and drop the passenger side down first to twist it out. Then to install you have to set it on the passenger side extension and lift it in . This is the only way we had clearance front to rear to drop it out, it will not drop straight down. We didn't remover the axles , little tight getting it back in but with two people it works.

    The replacement had 4 wires to the actuator while the old had 3 wires with two plugs like my 95 after I converted it. I haven't seen a complete wiring diagram of the actuator but I assume it has a switch to take the place of the old style switch on the extension shaft housing.
    If you still have the old thermal actuator and run into this you will need to have the harness kit and the new style actuator. The new style actuator is larger and made of plastic so it is easy to see. The actuator was left on the diff. so my brother now has a spare. I stole the plug from it and could make up a harness if anyone would need it sometime. I also machined a couple spare spacer plugs and have those. I priced that plug with pigtail when I did my conversion and found they want $40 for it.. crazy.

    I thought I would post this if someone else runs into this. It took us about an hr extra to decide what to do and do the swap on the extension. Sorry I forgot to take pictures.

    Might change my nick to The Story Teller :rofl:

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