Nobby
11-14-2008, 20:22
So in replacing the front pads I have discovered the following discrepancy that I need confirming/clarifying.
My Suburban is badged as a K2500. It has a 3:42 rear end SF axle and hence its GVWR is badged at 7900lb which is where the issue begins.
When I purchased new front pads my local auto store offered me only GVWR of 7200lb or 8600lb so being as my front axle is 8 lug I went for the 8600 offering. Turns out my existing pads were different to these but the new ones were able to fit in the caliper OK and were close to fitting. Back at the store my existing pads matched the 7200 offering. I suspected that the calipers would be the same possibly and a check showed that all generic makes except Delco showed the same caliper for both 7200lb and 8600lb. Now I want to get this right and get the right calipers and pads on this truck. I know that when I purchased the truck the calipers and pads were replaced as a kit so what are the odds that owing to the 7900 GVWR discrepancy the 7200lb calipers and pads were fitted which will fit?
Now as I understand it and please correct me if I am wrong I have the 8 lug front axle which is the 8600 axle. The 7200lb axle is a 6 lug. Except that don't all Diesel burbs have 8 lug?
If I understand my GMC manual correctly the 8600lb axle is a JD7 spec and has a 12.5" x 1.26" rotor. The 7200 is a JD6 spec and has a 11.57" x 1.25" rotor.
My truck is spec'ed as a JD7 with a vin# of G making the brake system 8000-9000lbs and would be referred to as a K3.
Now what is interesting is that the manual does discuss two kinds of 3400 Delco caliper one with a 75mm bore and one with an 80mm bore and I am assuming then that the 75mm is for the 7200lb and the 80mm is for the 8600lb and I am also then assuming that the aftermarket makes are lazy and just offer one caliper for both.
I know that this is no real biggy but the 7200lb pad is slightly smaller and so uses less of the available disc and a smaller bore caliper will obviously give slightly less effort.
Now furthermore this also reraises my confusion in regards to my 2500 badging. Seems as though the 3:42 was an anomaly for the 2500 as they usually started off with 3:73 and the FF. Now my assumption is that my truck got rated at 7900 because of the use of the SF axle. Now according to my VIN# the truck is a code 1 which makes it 1/2 ton? Now I am told that the rear spring packs in all Diesel Burbs are 6 leaf as is mine but then I just read somewhere that the thickness's differ and that a 1/2 ton burb rear spring is still different to a 3/4 ton burb. Can anyone input on this or better yet can someone with a true 3/4 ton VIN# code 2 (6th digit) suburban measure there leaf thickness's so that I can compare. I really would love to know what rating my springs are? To that matter anyone with a true 1500 1/2 ton suburban care to post up on there spring leaf thickness's and number?
Hey DaveNY you have a 3/4 ton FF dont you? Care to meet up for coffee so I can take a look?
cheers
Nobby
My Suburban is badged as a K2500. It has a 3:42 rear end SF axle and hence its GVWR is badged at 7900lb which is where the issue begins.
When I purchased new front pads my local auto store offered me only GVWR of 7200lb or 8600lb so being as my front axle is 8 lug I went for the 8600 offering. Turns out my existing pads were different to these but the new ones were able to fit in the caliper OK and were close to fitting. Back at the store my existing pads matched the 7200 offering. I suspected that the calipers would be the same possibly and a check showed that all generic makes except Delco showed the same caliper for both 7200lb and 8600lb. Now I want to get this right and get the right calipers and pads on this truck. I know that when I purchased the truck the calipers and pads were replaced as a kit so what are the odds that owing to the 7900 GVWR discrepancy the 7200lb calipers and pads were fitted which will fit?
Now as I understand it and please correct me if I am wrong I have the 8 lug front axle which is the 8600 axle. The 7200lb axle is a 6 lug. Except that don't all Diesel burbs have 8 lug?
If I understand my GMC manual correctly the 8600lb axle is a JD7 spec and has a 12.5" x 1.26" rotor. The 7200 is a JD6 spec and has a 11.57" x 1.25" rotor.
My truck is spec'ed as a JD7 with a vin# of G making the brake system 8000-9000lbs and would be referred to as a K3.
Now what is interesting is that the manual does discuss two kinds of 3400 Delco caliper one with a 75mm bore and one with an 80mm bore and I am assuming then that the 75mm is for the 7200lb and the 80mm is for the 8600lb and I am also then assuming that the aftermarket makes are lazy and just offer one caliper for both.
I know that this is no real biggy but the 7200lb pad is slightly smaller and so uses less of the available disc and a smaller bore caliper will obviously give slightly less effort.
Now furthermore this also reraises my confusion in regards to my 2500 badging. Seems as though the 3:42 was an anomaly for the 2500 as they usually started off with 3:73 and the FF. Now my assumption is that my truck got rated at 7900 because of the use of the SF axle. Now according to my VIN# the truck is a code 1 which makes it 1/2 ton? Now I am told that the rear spring packs in all Diesel Burbs are 6 leaf as is mine but then I just read somewhere that the thickness's differ and that a 1/2 ton burb rear spring is still different to a 3/4 ton burb. Can anyone input on this or better yet can someone with a true 3/4 ton VIN# code 2 (6th digit) suburban measure there leaf thickness's so that I can compare. I really would love to know what rating my springs are? To that matter anyone with a true 1500 1/2 ton suburban care to post up on there spring leaf thickness's and number?
Hey DaveNY you have a 3/4 ton FF dont you? Care to meet up for coffee so I can take a look?
cheers
Nobby