More info -- Rotors/Spindles -- 88-91 6 lug

[dennislbrooks]

I saw a 97 -- 2500 - 6 lug Cheyenne yesterday -- learn something everyday.

Anyway pics show a 71/72 rotor (5 lug in pic) that does fit on a 3/4 ton LD spindle and also shown is an 88 3/4 ton LD GMC 6 lug rotor. Both take same A3 and A5 bearings and seal. I have not tried yet but I believe the 72 or 88 calipers will work with respective pads. Not sure if the 88 caliper takes the same flex hose yet either. 1/2"-20 x 1.720-1.750 with a .615/.625 diameter knurl replaces the metircs wheel studs-- one has been replaced. I could not find a 7/16 with a big enough knurl. Should still work fne on oem 6 lug wheels. The 88 spindle takes the same 6117 lower ball joint -- the 71/72 takes a 6124 upper and the 88-91 (may be others) take a 6136 upper ball joint. The outer tie rod end on the 88 spindle is a rethreaded 88 to fit a 65-70 c10.

Anyone else have any info or experience on this?

[Hart_Rod]

I've got a nice set of 2003 suburban wheels w/tires if you need them.

Rob

[corn]

This thread has a ton of good info on conversions...

http://67-72chevytrucks.com/vboard/s...ad.php?t=35042

[dennislbrooks]

good thread for sure-- point here is also to interchange rotors from 5 or 6 lug. I list the 3/4 ton LD spindles to use the 6136 upper -- I have not found A-arm changing necessary --- but maybe -- there are things I do not know --- 87 LD 1/2 ton 5 lugs will go on 65-72 spindles with use of correct spindle year upper and lower ball joints (6117 and 6136)---- appears near all 1/2 ton 71-91 (may be higher) use the 6117 lower ball joints --even the 3/4 ton 6 lug LD. Does anyone know if the 71/72 calipers work on a 88 3/4 ton LD spindle? I suspect it may.

[SCOTI]

Originally Posted by dennislbrooks

I saw a 97 -- 2500 - 6 lug Cheyenne yesterday -- learn something everyday.

Anyway pics show a 71/72 rotor (5 lug in pic) that does fit on a 3/4 ton LD spindle and also shown is an 88 3/4 ton LD GMC 6 lug rotor. Both take same A3 and A5 bearings and seal. I have not tried yet but I believe the 72 or 88 calipers will work with respective pads....

This was my understanding: The 71~87 1/2T w/1.25" rotor & 88-up 3/4T 'LD' rotor both utilize the same inner/outer bearing...... Right?

If this is a true statement, why swap all the 88-up stuff? Why not just use the 88-up 3/4T 'LD' 6-lug rotor on the 73~87 spindle? The wheel studs will require possible changes but bearings & rotor width/diameter are the same. This would seem easier than locating the C20 3/4 ton lower arms just to use the 88-up spindles.

What am I overlooking?

[dennislbrooks]

I believe we are in agreement Scoti. I will pick up calipers/pads for the 72 and 88 this week to see the diff --will only purchase one pair -- hopefully the 72's as they are less expensive. Somethings ya just have to know. haha As far as the 88 spindles--just whatever is cheap easy to get at the time $10. I do not know if there are any differences between the 1/2 ton HD and 3/4 ton LD spindles -- I believe they are the same 73 up with exception of maybe the upper ball joint which both fit in the 1/2 ton 65-70 A-arms. Anyone know this not to be true?

[Geezer]

Post back what you find out please! I’m using 88 suburban spindles and have found that the 1991, 6 lug rotors have a different rotor centerline and the calipers won’t fit using them.

[SCOTI]

Originally Posted by dennislbrooks

.... As far as the 88 spindles--just whatever is cheap easy to get at the time $10....

Agreed. Cost is a big factor when making the decision of which selection of parts one uses, even more so when there's a tight budget. $10 bucks for the spindles (plus the 88 spindles are prob more plentiful in the yards) is a good price.

[dennislbrooks]

Good info Geezer -- will do on the posting ---- I have a 72 5 lug on one 88 spindle and a 88 6lug on the other 88 spindle --will get a pic side by side also

Ok--agree with offset --- for sure the left one takes an 88 caliper --one on right is a 72 rotor on an 88 spindle --will see if a 72 caliper works on the right one.

Looks like wheel to hub mounting surface is same height--hard to see in pics.

[70c10]

Dennis, after you get all this sorted out, you should start selling kits for all us 6 lug guys!. Thanks for sharing this info.

[dennislbrooks]

Ok-may help when trying to be scientific on the approach to be a scientist. OK --the spindles are from a 88 Chev G20 Van ---- the 72 5 lug rotors work on them with the 72 calipers and pads as shown in pic. 72 calipers are cheap even with no core.

I will pick up the pair of 88 G20 van calipers tomorrow evening to see if they work on the 88 G20 van spindles with the 88 3/4 ton LD 6 lug rotors -- I do know the 72 calipers will not work because of the offset. Stay tuned.

[SCOTI]

Keeping this one up front as we wait for our friendly 'scientist' to complete his experiments.

[dennislbrooks]

OK--- I tried the 88 G20 Calipers on the 88 G20 spindles which by the way are very near identical to 71-87 1/2 ton HD --- tie rod ends and upper ball joint may differ ---- and the 88 G20 calipers still will not work with the 88-91 3/4 ton LD 6 lug rotors. I really think as others alluded to that if you do not want to buy your 6 lug rotors from McNaughy's or similar then you need the 88 3/4 Ton LD spindles and calipers --I do not know if there would be brake line connection problem or not. 11/16 inch RH tie rod ends can be overcome if the spindles could be used at all on a 65-70. If any one comes across a 3/4 ton LD 6 lug spindle rotors and calipers take some pics or drop off at my house.

[SCOTI]

Dennis.... Is it the bearing race location/depth (relative to the rotor surface C/L) that's different? I can only assume that's where the difference would be if they can utilize the same bearings.

[dennislbrooks]

Bearing locations are fine. Machining of the lip seal is ok also. Just like Geezer said above the rotor is offset about 1/2 inch outward. I did have a caliper for an 88 3/4 ton LD and it is longer/larger than a 72 1/2 ton and a 88 G20. Next time I walk a junk yard I will look for some of these 3/4 LD parts.

[67 cst swb]

Guys... I already went down this road (I think)
I work at a Auto Parts Warehouse. I was thinking a 88-92 3/4ton LD rotor would go on a 73-87 spindle. I found the offset (where the inner race rode on the spindle) was too far outboard.
But, I see your talking about a "van" rotor. I can look at the diamensions of that today.
I do know, the adjuster sleeve on a 71-87 versus 88-92 are the same thread. I used the 88-92 LD 3/4ton spindle (88-92 1/2ton HD is same, only if 1-1/4 rotor thickness, but still need to use 3/4ton LD 6 lug rotor), caliper, rotor, & outer tie rod end. I did this so that I could get the aftermarket 2" lowering spindle. Now, if you do use the 88-92 spindle, you need to use a 63-87 3/4ton lower control arm as the ball joint diameter is the same. you can use your 1/2 ton upper with a 88-92 ball joint.
I see that you are looking at slightly different applicated stuff so, I will help you research this stuff. Even though I'm complete in my front end build. I'm always up for new knowledge.
You can email me direct at bryan@sturdevants.com and I can look at the parts spec's books to give you diamensions. So, email me the application on anything your thinking of using.

[dennislbrooks]

67 cst swb -- knowledge is good. I used a G20 van spindle which accepts the 71/72 5 lug rotor and caliper. The rotor I used was an 88 GMC 3/4 Ton LD -- and I agree with what you say. Unless you have the matching spindles installed--stay away from the 6 lug 3/4 ton LD rotors for use on 71-87 spindles.

[Bob Moore]

Dennis - I have one DUMB question - what is 3/4LD? What does LD stand for? I love this thread where we are trying to save money and adapt other parts to these old trucks.

Listen to this guy. He is a genius at adapting parts. 6 lug rotors, hydraboost, and probably other things we don't even know about yet.

Keep thinking - Bob

[dennislbrooks]

I learn as much from you guys -- LD means Light Duty --- take a look at rockauto.com for an 88-91 GMC C2500 2wd 350 eng -- brake/wheels/hubs - then rotors 7200#'s fronts


I saw 97 Cheyenne C2500 that had 6 lugs also -- and not a 4wd

[Deuce]

Can somebody put this in the FAQ section??
I love this site!!!

[dennislbrooks]

Bob Moore, sometimes my experiments have a downside... This is an ironicle joke -- but if any one needs 2 new 88 GMC 3/4 ton 6 lug or equiv rotors ----- let me know....... 8-) or drop off a pair of correct spindles.