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1970 blazer 4wd drum to discs need advice

J

JosR

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Hello to all, it's great to be a member of this awesome site. I just purchased a 70 k5 4wd 1/2 ton Blazer. The truck is 100% stock. I have been trying to get some good info. on converting my front end to disc brakes. The local mountain roads here in southern cal are scary as hell with these manual drums.... I hope to find someone that can tell me with absolute certainty if I can take the knuckles/hubs off a 71-72 and mount them to my 70 axle. I just purchased a 71-72 front axle complete and was thinking of just swaping the whole front end out, but I have not checked the gear ratios of either diff yet. I also don't know the condition of the 71-72 front end seals, so It would need to be gone through anyway. Any advice will be most welcome. Thanks, Josh
 
I kinda remember doing this @ 20 years ago. I also kinda remember having to grind brake calipers for some reason. sorry thats all I got!
 
Some early "pre-71" Blazers had the closed knuckle front axles I'm pretty sure...dont know if those can be converted to disc,or is worth doing..might be easier to swap a newer front axle in with the same ratio..master cylinder will need to be swapped also,they are different--.
 
I would swap the whole axle out. The early axles used a smaller axle U-joint than the later axles and is a weak point.
 
69 was last year of closed knuckle, drum brakes. 70 was open knuckle? drum brakes (rare, 1 year only brake drums and parts) and then 71-72 was open knuckle disc brakes. Id save your axle and try to find someone who needs 1970 correct, and source a 71-72 axle.
 
Thanks for the input everyone. My stock 70 drum front end is an open knuckle for sure. The only difference I can see physical on the outer hub is that the 71-72 axle I have has an aluminum cast lockout mechanism that you grab with your whole hand versus the stock 70 that you use your fingers to lock the hubs. It looks like I will be taking Scott's advice and going through the 71-71 axles and just swapping the whole enchalada. I still wish there were someone with a definite answer on just using the 71-72 stub shaft/knuckles out on my current 1970 drum axle , just in case the gear ratios are different. Thanks, Jos
 
Since your axle is an open knuckle everything will swap over if needed.
 
Thanks Scott. I will reply back with detailed pics and text of this to give something back to the forum. Thanks again. Jos
 
Eager to see your 70 K5. I've got a 70 also and I swapped in a 1978's Dana 44 to get disk brakes.
 
I was out today gathering parts. I picked up a set of reman calipers and I'm trying to hunt down USA made ball joints. The local auto zone and pep boys carried some taiwanese crap. I also am trying to decide what rotors to buy. Drilled and slotted versus stock oem type? Evil bay has quite a bit to offer for around $140/PR. I have decided to use the knuckles out on the 71-72 donor front end I purchased. The gears were 3.07's which matched up with my current 70 front end, but one of the spider gears on the donor had a tooth missing and I already know my original unit in the truck is in great shape and will only need some cleanup. More to come. Jos
 
ball joints = moog or trw

and dont get cross drilled rotors. go slotted if you wish. i have read a lot od crossdrilled warping faster and grinding pads up with the holes full of rust over time and mud and little pebels from mud.

but if you dont drive it much or do mud then prob be o.k.

and you swaping from drum to disk you will fell like a race car.
 
Ok fellas.... The verdict with proof is out. A 1970 k5 outer knuckle is slightly different than the 71-72 disc brake knuckle.The most notable difference is the placement of the outer knuckles six studs. I will post pics shortly. This difference causes issues with the caliper bracket placement, which in turn also causes issues with the caliper position, not to mention interference with the outer tie rod. As long as the knuckles outward, including the stub axles (71-71) short axle shaft are used, this project does work smoothly. Pics to follow soon.. Thanks, Jos
 
Sorry it didnt work out,but I feel better about my memory.On edit I did get this to work and drove the truck several years!
 
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