Rear drum master cylinder on J65 4 wheel discs?
 

I was doing a search on 1LE brakes and I ran across a GM service bulletin about the early J65, 10.5" 4 wheel disc brakes. It stated that if customers complained about the J65 pedal feel, that the dealer should replace the master cylinder with the one for rear drums.

Anyone know anything about that?

Re: Rear drum master cylinder on J65 4 wheel discs?
 

Re: Rear drum master cylinder on J65 4 wheel discs?
 

That's the one. Anyone here actually try it on the 10.5" J65 and feel a difference?

Re: Rear drum master cylinder on J65 4 wheel discs?
 

I was running 1LE fronts and J65 iron-caliper rears, switched to the drum master cyl as the tech bulletin described. Noticeably less pedal effort to haul the car down than with the J65 master cylinder, and no way I'd swap back. Highly recommended.

Re: Rear drum master cylinder on J65 4 wheel discs?
 

Do you think you'd get the same improvement with the 10.5" J65's all around?


BTW, were you happy with the 1LE front/J65 rear combo?

Re: Rear drum master cylinder on J65 4 wheel discs?
 

When I converted, I, too, swapped in the J50 master (along with the correct combination valve) as the 1LE conversion suggests. I don't recall the pedal feeling different, though I did this several years ago. I've since thrown on the so-called 1LE rears. The system is very nice.

JamesC

Re: Rear drum master cylinder on J65 4 wheel discs?
 

How big of a difference did adding the 1LE rears make for you?

I've also ordered the ANDYZ28 CD on the subject, to see what he's got to say. Hope it's 30 bucks well spent.

Re: Rear drum master cylinder on J65 4 wheel discs?
 

Enough so that I'd recommend the swap (besides I'm anal enough to like the front and rear calipers to match :crazy:)

I used Andy's CD way back when. If you haven't seen the following link, it might prove useful as well:

http://web.archive.org/web/200605221.../1LEbrake.html

JamesC

Re: Rear drum master cylinder on J65 4 wheel discs?
 

Yeah, don't tell me about being anal. :lol: I'm considering a 1LE conversion for the fronts on my under 11K mile '89 (rears are already PBR's). Yes, I know that the stock spindles are easily modifiable. But....I saw a pair of new, in the box, 1LE spindles on ebay a year or so ago, and couldn't stop myself from paying through the nose for them. But I'm not completely sure if that's being anal or simply insane. :crazy:

On my '83, I think I want to go with the cheap man's braking improvement route. Maybe, braided lines for the front, and the aforementioned J50 MC. We'll see....

Weird that the one I'm willing to spend all the money on, ALREADY brakes pretty darned good, now that I've replaced the original Gatorbacks with Goodyear F1's.

Re: Rear drum master cylinder on J65 4 wheel discs?
 

No idea on that one, google "Polishing a Turd" and you'll see.


They were very good for street/commuting use, but durability on road course track days was limited.

Re: Rear drum master cylinder on J65 4 wheel discs?
 

:lol:

Re: Rear drum master cylinder on J65 4 wheel discs?
 

Okay, here's the big question. Should I do it myself? This is kind of new ground for me. I've never removed and replaced a spindle for example. It looks fairly straight forward. Was it an easy swap? How much time do you think it took you to swap to 1LE front brakes? Any tips?

Re: Rear drum master cylinder on J65 4 wheel discs?
 

Yes, do it yourself. At the time, I'd never removed a spindle either and certainly never modified one, but it is, as you say, fairly straightforward. Easy? Well, spring removal/replacement can be dangerous. Time? Depends on how fast you work and how many obstacles you run into--for example the a-arm bolts, one or more, are likely seized to their metal sleeves. Two were in my car. They required an hour or so a piece with plenty of sweating, beating, yanking and cursing (done in French, of course, since it sounds much more dignified). Tips? If you're considering lowering the car, now's the time; now's also the time for struts and/or strut mounts as well as new bushings for the a-arms. Work slowly and carefully. The job isn't rocket science.

JamesC

Re: Rear drum master cylinder on J65 4 wheel discs?
 

Thanks for the encouragement James. Is it okay to reuse the spindle bolts or are new ones required? The car I'd want to do it on has low miles and has never seen any weather to speak of.

BTW, I usually curse at my cars in Greek. It seems like I'm getting my point across to them better.

Re: Rear drum master cylinder on J65 4 wheel discs?
 

I'd use new (we've already established that I'm anal) and swab them with anti-seize.

JamesC

Re: Rear drum master cylinder on J65 4 wheel discs?
 

Okay James, one more question and I'll leave you alone (for now). :D Is it better to fully assemble everything before you put it on the car, or is it better to install the spindle and then assemble the brakes?

Re: Rear drum master cylinder on J65 4 wheel discs?
 

Installing the spindle itself can be a bit awkward--and the weight of the rotor/ caliper would make it more so. Then, of course, there's the spring to battle with as well); as a consequence, I'd assemble the brake pieces last.

JamesC

Re: Rear drum master cylinder on J65 4 wheel discs?
 

It's a pain torquing the adapter-to-spindle and the bracket-to-adapter bolts off the car, much easier w/ the spindle secured to the ball joint and strut. The spindle was too bulky to try and secure on my bench vise, but not heavy enough to remain stationary during fastener tightening.

I'm much happier assembling the components onto the car, one at a time, tightening using an accurate torque wrench and Loctite red formula.