Disk Brake Conversion
Does anyone have experience using the disk brake conversion kit from LMC trucks? I have a 1966 GMC Fleetside, 351 V6, 4 speed manual transmission. I would like to convert the front to disk and keep the rear the stock drum. I have a teenager who will be driving soon and need the piece of mind that she will be able to stop the truck with the power assisted disks.
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Re: Disk Brake Conversion
Doing a disc brake conversion on these trucks is a good idea for the reasons you mention (safety), but I would caution against the power disc option for the simple reason of potentially "locking up" the brakes in the case of a panic stop. Once the front (or rear) wheels lock up, it's game over, and you are very quickly out of control. It is hard to regain control from this, even for a very experienced driver. Your vehicle suddenly starts tracking in a direction that you do not want it to go in, like sideways. The exception would be having a power disc brake truck that utilizes the anti-lock feature found on virtually every modern car or truck made today, making these newer vehicles very safe in almost any hard braking situation. Quite honestly, I do not know if this is feasible in older trucks like ours, or even is available. If anti-lock is available, it would probably be very expensive to retrofit to a 60's truck. Don't really know, or care for that matter.
I have found out myself from doing two non-power drum-to-disc conversions conversions that power assist is not necessary if properly designed. My first was not a truck that we talk about on this forum, and the latest one is a 65 GMC Suburban that has OEM (all General Motors hardware except the front disc rotors) under the truck. Quite simply, I put a 1979 GMC (or Chevy- same hardware) under the front of my '65 that is a non-power version. One of the main benefits to doing this is having all GM parts with gobs of R&D that went into it at the factory, so any parts you might need in the future are readily available from a variety of sources. Another added benefit worth talking about is the size of the hardware increases, and you wind up with much more robust and durable (in size) upper and lower ball joints and tie rods and ends, so greater strength is achieved. Tie rods on a stock 60's truck is like the thickness of your little finger, vs. tie rods on a 73-87 GMC or Chevy truck is like the thickness of your thumb. Major improvement, and looks just like original, because in a sense, it IS original. Going aftermarket you will be adapting disc components onto the smaller 60's era ball joints. There are several upgrades to disc front that can be readily had and installed from a variety of aftermarket competitors, just do your homework and ask questions. Nothing wrong with that. I have no experience from LMC Truck on this, but I will tell you that I purchased a power steering box adaptor kit from CPP to put a power steering box onto my 65 GMC, and found that although the cost was only $60 or so, it was junk, and I wound up throwing it in the recycle can. I wound up going with Captain Fab on power steering conversion, but I digress. Doing what I did in swapping out the entire front suspension from 1965 drum to 1979 disc is pretty straightforward. The whole front suspension crossmember you drop out with 6 or 8 bolts total, you wind up installing a 73 to 87 front suspension into the same physical position, and all the bolt holes line up with the exception of 2 that you need to elongate to get the bolt through, and 2 that you need to drill. The important part if you go this route is finding a suitable donor truck whether it be power-assist or not, is to get ALL of the braking components from the donor truck. This includes the master cylinder on the firewall, brake lines that feed the front, and most importantly, the proportioning valve for that vehicle that feeds the front and rear brake lines. All I am trying to say here is DO NOT try to invent your own braking system. Do not think that "well.... bigger is better, so I'm going to make this line a 3/8" instead of the 5/16th" line that it was designed with." Stick with a proven and reliable design that the factory came up with at the time. To others who may be contemplating this move, beware that the 60-63 GMC trucks use a hydraulic line off the master cylinder for the clutch, so a conversion to a later model truck's braking system will not work in this situation, and you would need to convert your clutch from hydraulic to mechanical linkage, something that can be done but with some challenges in finding the right hardware for converting this. I believe that 64-66 GMC's all have a mechanical clutch linkage, and if so, you are golden for converting your braking system- just check yours to be sure. I am very happy with the front disc conversion that I did with using parts from a 1979 non-power brake truck on my 65. Yes, I can lock the brakes up if I want to, but who really wants to do that? Braking is one of the most important things we can improve upon from a safety perspective. Most of us really don't care how fast we can go- that is another discussion. I kept and used my original 65 coil springs and put them into the 79 upper and lower spring pockets of the A-arms. I just made sure that I put them back onto the same side. This makes my ride height the same as it was before I started. If you leave the coils in place from whatever year donor truck you might be using, then you could potentially be looking at a different ride height up front. Just something to consider if going this route. Happy trails, and keep on truckin! |
Re: Disk Brake Conversion
Jim, thanks for the reply, I really appreciate the input. I have been contemplating finding a donor truck for this conversion and now I will stop contemplating and start looking. :signthankspin:
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Re: Disk Brake Conversion
Has anyone used the front disk convertion kit from Ecklers?
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Re: Disk Brake Conversion
Hello,
Sorry for the long delay in response, but I do not spend a lot of time on this website. I am glad to hear that you went the route you did with buying a donor truck to do your upgrades, and you are right that buying a "kit" can easily cost more than an entire truck! Good for you! |
Re: Disk Brake Conversion
Just a note about my reference to "panic stop"..........
You might want to try this yourself on a lonely road (or a big empty parking lot) with nobody around to see what happens when you mash down on that power brake pedal. One of the BIG things I really like about non-power is that I have GREAT control over the braking system and can lock them up if I want to with increased pressure on the pedal, but I prefer not to. It is the closest thing to "anti-lock" without all of the expense in doing this sort of modification. R/ Jim |
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I will give it a try. I will just have to put a pillow over the steering wheel first! :lolsmack2: |
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I do understand the value of discs over drums but you have to sacrifice your stock wheels and stock hubcaps when you do that, so the tiny gain in stopping power is simply not worth wrecking the original appearance of a totally stock truck over. Just my two cents - I never see posts where anyone is suggesting use of the factory available power parts but they are well worth considering if you ask me |
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Having driven vehicles with and without power brakes... I can't honestly say there is much difference. The pedal on power brakes seems to activate easier, but stopping has been about the same. Anti-lock is always questionable, several of the vans my wives have had were rear-antilock, which never made sense because the front (steering) could lock up then and you'd lose control. Also when the anti-lock feature failed, there was no difference in driving (except the annoying light on the dash). A lumber company I worked for had anti-lock on the 1/2ton Chev pickup we used for small deliveries and "running around", you had to learn to apply brakes sooner than normal because they felt like mush (shop said they worked perfectly) and it took longer to stop. I *assume* that was the anti-lock since if you had to try to stop quick you could feel the pulsing in the pedal, and if you stopped in time it was a miracle. Drum brakes are just as good as disc, both stop the vehicle. Manual stops you just as fast as power, it just takes a little more pressure on the pedal. Anti-lock and power systems are also just one more component that can fail, brakes are real simple and don't really need to be made more complicated. But that is my opinion, based on driving a wide array of vehicles over the last several years. |
Re: Disk Brake Conversion
David
I found a recent post of yours where you commented on doing a 1/2 ton to 3/4 ton conversion. Did you use a donor truck? I'm looking at using a 1978 GMC 3/4 ton as my donor, but trying to research to make sure the cross member will swap without major modifications. |
Re: Disk Brake Conversion
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-BUT- One was a fairly complete and running '66 1/2 ton and the other was a chassis, cab and bed '66 3/4 ton. So everything swapped over because... well, same year. We did not complete the swap though since someone was interested in buying the truck, and intended on replacing all the axles anyway (modern disc brakes, etc). He bought both trucks, and some loose parts I had. Funny thing is he was a Chevy guy but knew about the 305. The way he talked he sounded like he was going to hotrod the truck, but keep the 305 to be different. I really didn't want to sell all we did, but the money was good and needed. He even paid "the kid" (who is living in a 5th wheel in the yard with his fiancee while they try to find a house) to help him haul. Worked out good all around for us. And we (I mean the kid) didn't have to finish the swap. Just had to put it back together enough to get on a trailer. |
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Re: Disk Brake Conversion
Hello Suburbangeorge,
I do not have anything against power brakes other than (a potential for) lock-up. Some people will have nothing but. I prefer the look of a non-power brake setup under the hood- no gargantuan booster drum to look at or get in the way of any maintenance that one might need to do. For those that choose power brakes, there is plenty of room under the hood for a brake booster. I like the control that you have with non-power (disc) brakes. As I mentioned in my original post, a panic stop can cause your brakes to suddenly lock up, and without the booster, locking up the brakes is, simply put, not as easy to do. I don't need to talk to anybody about what parts I need, because I am quite pleased with what I already have, and just thought that I would share my experience with others that may be looking for input and others' experiences. My "experience" originally came from researching and reading about automotive brake systems, and some of that which I was reading was telling me that a properly designed braking system does not need to be power-assisted with a vacuum booster, so this is the approach that I took, and by golly, all that reading and research paid off. The original goal for me was to replace the front drum with disc on my 65 Sub, and it all worked out very nicely. You did admit that you should "probably read this whole thread" before picking on me. I wholeheartedly agree with that statement. Cheers! |
Re: Disk Brake Conversion
I know this isn't staying in line with the conversation completely, but I just did a front disk swap In my 65 3/4 ton. Basically i only spent around $200 for the entire swap by finding some 8 lug 84' C20 disk brakes from the junk yard. Surprisingly, the 84' ball joints are the exact same size as the 65' ball joints as far as fitting into the control arms. Only the shaft that fits in to the brakes is slightly different. And that's it. I got the brakes, cleaned them up, installed the 84' ball joints and put it back together. I still have 8 lug all around the truck and now have some seriously beefy disks on the front now. I have a daughter I need to keep safe as well so I get were your coming from. I also understand that having a child can hinder finances a bit too. So maybe this is something that can help you out a bit.
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Re: Disk Brake Conversion
Drewski, I gather from what you laid out is that 3/4T trucks use the same ball joint sizes for the 60's through the 80's. This should help out some other folk who may be considering some kind of front-end swap for better brakes using disc up front.
In my own 1/2T experience, I found that basically everything on my 65 was smaller than what the 79 donor truck had. This includes ball joints, control arms, center drag link, and also the anti-sway setup that my 65 just happened to have as factory OEM. I'm sure you will be happy with having disc brakes up front. I am very happy with mine. |
Re: Disk Brake Conversion
Jimjaz, thanks for that info. I had no idea that a 1/2T would be so much harder. I honestly don't have much experience with the 1/2T. I would have to thank jollys write up about how he did this type of swap on his 1 ton. I read that about a year and half ago and said to my self "I bet I could do that on my 3/4T. A bit of research and a bit of a what the **** attitude got me to try it out. I was definitely pleasantly surprised. I needed to upgrade to disks because the wife is on the hunt for a camper to start hauling around. That and I live in Albuquerque were the drivers are the worst I've seen, and I've lived in 3 countries and all over the US.
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Re: Disk Brake Conversion
Drewski, I had to laugh about your comment on Abq drivers being the worst. We must all feel that way about where it is we live- I have that very feeling you describe about Phoenix metro. I could not survive in this place if I had to do a M-F, 8 to 5 gig and be exposed daily to all the morons around here on the streets and freeways who THINK that they have self-driving vehicles the way they text and drive. I would either have to shoot myself or someone else the way they drive around here. I think we hold the gold medal for the number of wrong-way drivers in Arizona! If I have to drive somewhere to get something done on a day off, I try to dial my travel time in between about 10AM and 2PM as the rest of the time it's like a big giant parking lot with lots of people who think that if they ride up your ars real close that this will make the person in front of them go faster. Cheers!
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