magnumP5's RX-7 Build Thread

[magnumP5]

When I put 06 MS6 brakes on my MSP I skipped the 929 master cylinder because the bore on the MSP (626 V6) brakes are the same as the bore on the assessor's 06+ MS6 brakes and I liked the stock pedal feel and travel.
I you are increasing the bore size on your calipers the 929 master cylinder is a great upgrade. If you want less pedal travel it is also good, otherwise skip it.

I'm doing the swap for better pedal feel and less travel. Even with SS brake lines and a completely bled system the pedal has to be nearly on the floor to lock the brakes.

Yes you have to swap the output shaft.

Are you talking about the shaft with the harmonic balancer? I spoke with Mazdatrix yesterday and according to them the only items kept are the housings (bell, intermediate, and tail) and the actuator rod. Everything else (gear set, bearing plate, selector rods, ends, and forks, etc.) is kept from the Miata. The input shaft (on the front of the mainshaft) has to be machined a little (made shorter) but that's it. According the them they've not run into any issues running without the harmonic balancer. I never thought about it but I guess you've gone through this similar process.

 

[Sport23]

I'm doing the swap for better pedal feel and less travel. Even with SS brake lines and a completely bled system the pedal has to be nearly on the floor to lock the brakes.

Yeah, the pedal feel on my 7 is horrible but I didn't know if that was just my car or not. Sounds like a good upgrade for the 7 and not needed for the MSP (unless calipers with a larger bore are used.) Keep up the good work man!

 

[magnumP5]

Yeah, the pedal feel on my 7 is horrible but I didn't know if that was just my car or not. Sounds like a good upgrade for the 7 and not needed for the MSP (unless calipers with a larger bore are used.) Keep up the good work man!

No matter how many times I bled the brakes I couldn't get a better feel. I know the MC is still good because I found no leaks and the fluid level never changed. Hopefully I'll be picking up the new MC and booster tomorrow. My plan is to rebuild the MC and clean up and paint both parts before installing. I'll need to change my vacuum lines a little as the vacuum port for the 929 booster is on the opposite side.

In general not really any updates on the RX-7. I got in touch with someone in TN who made his own "SST's" for the transmission teardown and he's going let me borrow them for a while. It'll probably be a while before I get those and I'm still waiting on the exhaust manifold and fiberglass body parts so I don't expect to make much progress this weekend. Since the weather is going to be warmer I guess I'll focus on cleaning up the transmission housings and preparing them for paint.

 

[Sport23]

My master cylinder was bad when I got my RX-7. I replaced it but never got a good pedal feel either. Let us know how the 929 works out for you; I have a feeling I will be swapping to one also since it's on my shelf already. (thumb)

 

[Plx92]

This is one of my favorite fc's! awesome build man your attention to detail is killer!

 

[magnumP5]

This is one of my favorite fc's! awesome build man your attention to detail is killer!

I spent a good amount of time in the garage this weekend and got seemingly nothing done. I was finally able to remove the large lock-nut, which holds the harmonic balancer, with some large channel-lock pliers and a vice. There were some equally annoying wedge-type spacers holding the balancer in place but I was finally able to remove those by pushing the balancer back first. I may need to start labeling the transmissions as they're starting to become indistinctive:

After that I knocked out the roll pins and removed the selector rods ends and pulled both intermediate housings. Now the 5th/reverse assemblies are exposed.

That's as far as I can go now without the tools needed for further disassembly. I'm essentially done with the RX-7 gear set as all I needed was the intermediate housing. I still may disassemble it for "practice" before tacking the Miata gear set. I have to remove the entire 5th/reverse assembly and remove the bearing support plate to separate the input shaft from the main shaft. With work halted there I spent the rest of my time trying to clean 24 years worth of oil residue and road grime from the transmission housings. I need more brake cleaner...

I also picked up the 929 brake booster and master cylinder. I don't remember the booster being this rusty when I looked at it last week.

The inside of the booster and backside of the MC were both completely dry so I assume the leak is from seals at the bottom of the bottle. I took a wire brush on an angle grinder to the booster and forunately it's only surface rust.

It's pitted pretty badly where the rust was but fortunately no holes. I need to pick up another wire wheel to remove the paint from the backside then I plan on hitting the whole thing with several layers of hot temperature primer, paint, and clear. That should keep it from further rusting. The MC cleaned up pretty decently with some solvent and a wire brush but I'm not done yet. Now I need to order a rebuild kit for the MC, some new seals for the bottle, and a double banjo fitting.

 

[mymmeryloss]

I tink u shoulda just gone woth a wilwood pedal setup and got rid of the booster altogether...

 

[magnumP5]

I tink u shoulda just gone woth a wilwood pedal setup and got rid of the booster altogether...

That would require more work than I want to do right now. I really don't feel like ripping the interior out all over again. I'm not sure I'd like the feel of unassisted brakes at this point either.

I finished cleaning up the booster last night and I tackled some misc transmission pieces as well. I decided to then work on the MC, which turned out to be a mistake. The MC itself is fine but I ended up breaking the reservior while trying to remove it. I also found out the cap was leaking. Now I'm trying to find a new reserior, which is proving difficult. I've read most MC reserviors are similar but I need to find one large enough that also has the provision for the brake fluid level sender. I'm now probably looking to spend more an a new reservoir and rebuild kit than I did on the MC itself. Ugh...

 

[magnumP5]

I decided to then work on the MC, which turned out to be a mistake. The MC itself is fine but I ended up breaking the reservior while trying to remove it. I also found out the cap was leaking. Now I'm trying to find a new reserior, which is proving difficult. I've read most MC reserviors are similar but I need to find one large enough that also has the provision for the brake fluid level sender. I'm now probably looking to spend more an a new reservoir and rebuild kit than I did on the MC itself. Ugh...

New reservoir from Mazda is $150. No, thank you! I decided to give up on this MC and go with a new aftermarket Dorman unit for $74. I'm taking a bit of a risk by going with a non-ABS unit ($25 savings) but I'm pretty sure the MC is actually the same and the fittings are different. Of course this defeats the purpose of having a matched set but hopefully the new MC will play nice with the booster as I don't have the SST's to properly adjust the booster plunger. I guess I could always take it to Mazda...

 

[Sport23]

Will they RX-7 Reservoir swap over to the 929 master cylinder by chance?

 

[magnumP5]

Will they RX-7 Reservoir swap over to the 929 master cylinder by chance?

This was my first thought but I'm pretty sure the spacing on my N/A FC reservoir is different. Besides, given the age of my stock reservoir it'd probably break if I looked at it funny. I know the FD ones can be swapped and perhaps the TII FC as well but unfortunately I have neither and they're all pretty much $150 or so. The 929 MC itself seems to be in pretty good shape so I plan on keeping it if I need a rebuild or I don't like the Dorman part (I'll just swap the reservoirs). Regarding "matching" the new MC with the old booster I'm going to assume the old MC was matched just fine and take measurements of both MC's and adjust the boost pushrod accordingly. If nothing else this'll be a pretty good starting point.

I got the "modified" tools for the transmission disassembly yesterday. I ought to take a picture of the socket because it's ridiculous. Imagine a 44 mm socket that's about 15" long! Unfortunately the modified puller arms are too short, which is weird, but it shouldn't be too hard to pick up some more flat stock and make longer arms.

 

[magnumP5]

Talked to Shine Auto Project last night. My new FRP parts should be done and ship this week!

 

[ngd298]

Don't worry about the master cylinder reservoir breaking if it's anything like mine. I changed my MC today and had to pound the reservoir with a hammer to get it back on and it didn't even think about breaking. (I'm not the most patient person in case you guys haven't figured that out already..haha)

 

[magnumP5]

I spent the weekend in the garage working on the transmission. I was able to get the transmission disassembled as far as I care to go.

Started simple by removing the gear selector rods and clutch forks. There are a bunch of springs and steel balls in the bearing support plate that like to fly out when the bolts/rods are removed. It sure was fun chasing them around the garage (set the stage for the day I guess).

Here's my method of organization. I taped the parts onto cardboard and scribbled down the disassembly number from the FSM on the tape. I also tried to note what gear/gearset. In the end I have two of these cardboard pieces completely filled.

My "modified" puller to get those hard-to-reach bearings and clutches. This was probably the most useful/frustrating tool of the weekend.

After that I basically forgot to take pictures because I started to get pissed off. It's stragithforward in theory. After the bearing there's a huge, 44 mm locknut, then the 5th gear pinion and bearings, then the 5th/reverse clutch, and the reverse pinion and bearings. The locknut took some effort bit I finally broke it loose (over 150 ft-lbs). The 5th/reverse clutch was annoying because there literally wasn't any surface for the puller to grab. I ended up completely diassembling it (pretty simple, actually) and carefully working around the reverse synchro to pull the clutch off. What took the cake for being the biggest PITA was the countershaft. According to the FSM a few taps with a brass hammer is all that's needed to break the mainshaft and countershafts from their bearings. The mainshaft popped right out of it's bearing but the countershaft didn't want to cooperate. I ended up having to pull it and its bearing out of the bearing support plate, which involves a few extra steps I was trying to avoid. Shortly after removing counter shaft bearing:

Note the lighting change - it was well after dark by this point. You can see the giant-ass socket used for the mainshaft lock nut in the background. Quick shot of the countershaft (top), maintshaft (middle), and bearing plate (right) all separated.

You can see the bearing still on the countershaft and the mainshaft bearing still in the support plate. Both have been removed since that picture was taken. All that work just to get to this:

The "input shaft" and second gear pinion. The input shaft needs to be cut down a bit to fit with the RX-7 transmission cases. Once that's done I get to clean all the individual pieces and reassemble. The synchros all look good so I've no plans to replace them now. I spent the better part of Sunday cleaning 24 years of demon sludge (road grime + engine oil + transmission fluid) off/out of the transmission cases in preparation for paint.

 

[magnumP5]

Still need to find a machinist willing to modify the input shaft. In the meantime I've decided I'm going to completely disassembly the mainshaft so I can inspect all the gears, clutches, and synchros to confirm they're all okay. This'll also give a good opportunity to clean everything before reassembly.

One thing I've been considering lately is to mix/match gears to make my own custom gearset. Currently the Miata gears 1-3 are taller, but closer together than the RX-7 gears. 4th is the same and the RX-7 5th is MUCH taller (.697:1 versus .814:1). Since I'll never use 5th on track I'm considering swapping over the RX-7 5th to keep as a "highway" gear.

 

[magnumP5]

Not much love in here. I must be getting boring.

I was inspecting the countershaft last night and I found very small surface chips on two teeth. I'm not sure if they were already there or I caused them while removing one of the bearings. They measure maybe .06 x .10 x <.01 inches and are both on the "non-loading" side of the teeth. The FSM doesn't give any acceptability limits for wear or damange on the countershaft so I'm not sure what to do right now. I really don't want to replace the countershaft because that would either require finding another transmission and disassembling it or buy one new, which I haven't been able to find and I'm sure is expensive as hell. I plan on beaking any sharp edges so would there be any harm in reusing this part?

 

[o0n8]

I'm still following, just not posting because this is way beyond my intelligence at this point

 

[Lewis7789]

I'm still following, just not posting because this is way beyond my intelligence at this point

+1

I don't want to be annoying and post "Looking good, brah!".

 

[magnumP5]

I'm still following, just not posting because this is way beyond my intelligence at this point

+1

I don't want to be annoying and post "Looking good, brah!".

I'll admit I was really intimidated at first but it's really not all that complicated. The hardest part is having all the right tools and keeping track of everything. At least the differential and transmission are separate.

 

[eprx799]

Jon I've been following this threads as well. I would love to borrow/rent your specialty tools when you are done. I have a spare gear box I would like to rebuild so I have a backup.