I'm hoping to get some help finding brake parts for my gmc L4000 tilt cab. I'm in search of a master cylinder and wheel cylinders. Attached is a few pictures of the SPID and master cylinder. I've got a Chevrolet parts book but I'm not having any luck finding the master cylinder.
This master cylinder seems unique in that the bore for the clutch is smaller than the bore for the brakes.
I was lucky with my 1969 T50 Chev, the previous owner had just replaced the master when I bought the truck. He told me that he got it at NAPA but that it was one of two in the country at the time. That was about 6 years ago.
I would suggest that you look for a company to rebuild the ones you have, usually done with a brass or stainless steel sleeve installed. Not cheap but it would be the last time it would have to be done.
Hy campbell45, it is very common that the bore for the clutch side of a hydraulic clutch/ brake master be smaller on large trucks as the trucks usually have multiple wheel cylinders to supply through the brake side of the master cylinder. Some research revealed that the standard master cylinder (1 1/4" bore Raybestos p/n MC36212) is no longer being reproduced, the heavy duty master cylinder (1 1/2" bore) is available through Napa as their p/n NMC P55385 $79.99 + $37.14 core charge. I'll check on the wheel cylinders and get back to you.
Hy again campbell45, wheel cylinders, I checked Napa and RockAuto, RockAuto was cheaper by half, all part numbers are Raybestos, front WC 8852 $15.95, WC8853 $15.95, rear WC37095 $76.79, WC37096 $78.79, hope that helps.
Thank you so much for helping me with part numbers. After scouring the web, I think I did find the master cylinder you referred to with the 1-1/4" bore. It is a Centric part: 130.80018, which looks to still be available. What do you think? https://centricparts.com/part-detail/13080018
For the wheel cylinders, do you know if the front cylinders can be both used for top and bottom? I ask because my front axle has two wheel cylinders per wheel (top and bottom).
Another question, do you know how to identify GMC medium duty VINs? I say this is a 1966 because thats whats on the title but Id like to know what my VIN means: LV4016026451G
Hy campbell45, the wheel cylinders have different part numbers probably because they are handed or for forward and reverse or upper and lower applications. Unfortunately I'm a Canadian and my American parts books and maintenance manuals are few and far between, so I can't help with deciphering your serial number. The master cylinder you found looks the same as the others I have seen for your application, good luck.
I wanted to give an update. That Centric part number (130.80018) above is WRONG! Attached are a few pictures of the comparison. Based on my extended research, I am in need of part numbers: NMC P55385 (NAPA), 130.8002 (Centric), MC36347 (Raybestos), F54834 (Wagner). All of which are I believe obsolete. However, I did find an ebay seller that has new-old stock on bendix units that are exactly what I need. https://www.ebay.com/itm/224004132162
I will continue to update this until I have all new brakes. I hope it helps someone else down the road.
Thought I'd give an update. I've gotten the front brakes rebuilt and gave my best shot at bleeding. Pedal goes to floor but if I keep pumping, I eventually get a stiff pedal. The master cylinder keeps drinking fluid and I couldn't figure out where it was all going...until the next morning I found a puddle at the left rear wheel. Guess I need to rebuild the rear brakes too.
Attached are a few pictures of the rear backing plates. 3B found some part numbers for rear wheel cylinders, WC37095 or WC37096, but the mounting hole orientation looks different than what I have.
3B, do you have any thoughts on this?
In the meantime, I'll work on pulling the rear wheel cylinders to inspect.
Hy campbell45, I am wondering if someone swapped in an older rear axle, all the wheel cylinders listed for 1966 have seats for flared connections and your pictures obviously show banjo bolt connections. Try looking up Raybestos WC19746, which is correct for some 1964 models, hope that helps.
3B, Thank you so much. I think that's my issue - maybe its not a 1966! I just assumed it was based on the title. The WC19746 definitely looks like the correct wheel cylinder. These are also cheaper which is nice. For what its worth, the SPID shows that this rear axle is a rockwell g361. I'll try to find a axle ID plate to confirm.
