Drums to Disc

[68gmcjon]

I'm wanting to change from all drum brakes to all disc brakes. Does anyone know of some cars disc and calipers, etc. that would fit a 68' GMC 1/2 ton. What all would i have to change? Master Cylinder, booster, and others. Any help would be appreciated.

[1971Stepside]

For the front you will need new spindles, rotors, calipers and hoses. I have a set of stock spindles and rotors if you are interested. For the back you could try various 9" Ford applications or newer Chevy trucks (they have 6 bolt wheels though) or you can buy the kit for the rear for $600. You will need the booster and proportioning valve.

I spoke with the guys at Early Classics and they recommend not going with disc in the rear. They say they have tried several ways and each time it does not work well at all. They can't get it proportioned correctly. They actually have talked me out of converting the rear to disc on my 71.

Hope this helps some. It will not be a cheap job to do.

[Southpa]

I found that the easiest way is to do a complete front end swap with a 71 or 72. If you can assess the condition of your front suspension, steering linkage etc. and if you find you will need to replace some things anyway (like ball joints, tie rod ends, etc.) then that is the way to go. Just find a donor truck of those years with better susp./steering components. Its much less hassle than having to pull everything apart. You would need the master cyl, prop. valve for a disc brake truck. If your booster is still good you can use that. 71 and 72 wheels are 5-lug, btw, so you will also be needing to change rims unless you pick up some aftermarket 6-lug rotors.

I heard that rear discs from late 70's Cadillac Seville will fit our trucks with minor modifications. But I won't go hunting for that setup unless its right under my nose for really cheap. Most of the important braking power involves the front brakes anyway.

[slam33]

rear set up is 78 Caddy Seville but there a 5 lug and you have 6. Try Early Classics, they have a 6 lug set up.

[68gmcjon]

Thanks for the help. I am know considering just changing the front to discs now. Would i still need to get new master cylinder??

[Longhorn Man]

Yup, still ned it.
The rear brakes are only responsable for about 30% of your braking...and I think that is ballooned a little.
I drove for 2 or 3 years with the hyd lines on my rear brakes crimped off. You could hardly even tell, then when i installedd rear discs on the same car, the braking was improved, but no way was it worth the $$ i spent on them.

[muscletruck]

whoa longhorn....man you got lucky....i heard when you crimp the back brakes on any car or any brake line it can cause the others to lock up......MAN my brother was a dumb @$$ and did it to his CRAPSTANG cause he didnt wanna buy new wheel cylinders for the back...as soon he stepped on the brakes the fronts would grab and it would stiff and ****ty from there....he finally sprung for the cylinders when he was going down the freeway around 110 and the front wheels were smoking cause the brake pads were wearing down!!! GOT LOVE F@RDS

[ChevLoRay]

I am so happy with my Early Classic drum to disc conversion, that sometimes I just want to spit! Oh, what a feeling....brakes!!

Seriously, you won't regret the change. I bought the whole package from Early Classic Enterprises. Everything was there. All the brackets, bolts, brake lines, clamps, hoses, calipers (pre-loaded with pads), rotors, bearings, seals, master cylinder, proportioning valve, etc., etc. Oh, yeah, the spindles. You'll have to change the spindels, but their spindles give you the option of maintaining the stock height, or dropping it 2.5-inches.

If there is a down side, you'll be looking at the springs, ball joints, tie-rod ends, control arm bushings and shafts, etc. No better time to replace what needs to be replaced.

In the end, following an alignment (mine went back to factory specs, even tho dropped), you'll enjoy the drive. It's the best investment that I have made since I bought the truck 3 years ago. The suspension/brakes were done almost a year ago. No problems.

Plan on spending about $1200, plus labor, if you replace all 4 springs, rear shocks and add the adjustable track bar, which gets you the spindles and the complete conversion kit (minus power brake booster). My truck had power brakes before I made the change. Add $$ for the additional items to be replaced. My cousin did all the work on my truck for $300 (at home, after hours). All totaled, I have about $2K in the chassis, including 2 new tires on the front, the alignment and all of the above stuff. Thought it would be good for you to be prepared. It ain't cheap, but it was the right thing for me.

[Snowbound]

You don't need to spend $2K to get front discs! I picked up a complete front frame clip from a '79 C-10 off a farmer for $25. (He'd made a trailer out of the box) Swapped the whole thing over - bought new calipers and pads, machined the rotors, new upper ball joints, replaced the brake lines, bought some 5 lug rallies, and swapped the rear end also from a '71 GMC. All in total I spent maybe $400 on everything. I did it all myself in the driveway in the middle of winter ( only when it warmed up to about 10deg F) This was my first attempt at any serious mechanical work, so with some help from the guys on this board anybody can do it!

PS - was at the pick-a-part on the weekend and saw a late '70's Caddy with rear discs. I think it was a Fleetwood. Very tempted to grab everything, but I didn't have my coveralls with me. Damn!

Brian

[Southpa]

Good score Snowbound. Another driveway mechanic, lol. I picked up my 71 disc frontend for $200 over a year ago. I'm still using the same pads that were in the calipers. I guess I should have grabbed the rear axles because I have hybrid wheels now (5-lug in front and 6 in back). My old front end was really shot and dangerous to drive. I tossed it a while ago and then realized that it had almost new shoes. Kicking myself now.

[ChevLoRay]

I didn't spend $2K to get front discs ONLY! I got a whole buncha stuff and about $300 was for labor. I know everyone can't do it the way I did...I got a "package" when I got laid off/job elimination/retired, last year. I had an opportunity to do what I had been wanting to do with my truck. My parents are elderly and I help take care of them. My cousin is healthy and an excellent mechanic who likes working on older stuff for variety, i.e., simplicity.

I have no problem with those who can and want to do their own work. I did when I had no choice. I am older now, and not as able to do what I used to have to do to get by. I still do a lot of work on my truck, myself. I was merely telling the board what you get for what you pay, and what to expect to spend if you go the route I took. I know there are cheaper ways to go about doing a disc conversion. That's the great thing about America....the Freedom to choose the way you do things. Knock yourself out. I'm happy with what I have and I am happy that I had the money at the time to do it the way I did. Whichever way you go, it will be the best way for you...otherwise, you won't do it.

[minibike]

I would get the 71/72 spindles and use the correct ball joints for 71/72 in your 68 a arms. The linkages are different, so you would want to grab those off the doner truck, as well.

[Snowbound]

ChevLoRay,

Didn't mean to offend you. Just pointing out that there are cheaper alternatives to buying a package. I know I'd get scared off from doing the swap if I had to spend even $1000. And doing it myself was a good test for me, as my father is a mechanic and did all the work for me growing up. It was a chance to prove to myself that I could do it, and really it wasn't very difficult using only simple hand tools and a couple jack stands.

Peace!

Brian