magnumP5's RX-7 Build Thread
- Thread starter magnumP5
- Start date
This ^
I am paying attention though, my transmission is making all kinds of noise and grinding, so I might be down this road pretty soon..
Unfortunately they aren't my tools - I borrowed them from a member over on Rotary Car Club (FC Zach). I can ask him if it's okay to send to you when I'm done. Regardless they really aren't that complicated to make. The puller is just a standard 2-jaw with new arms made out of 3/16" x 1" steel. I probably could have made this myself if I had a puller handy (I had to make longer arms anyway). The socket is a little harder because it involves cutting a standard 44 mm socket in half and then welding each half to opposite sides of a long steel tube. I'm sure the socket is easily found but I didn't have the means to cut it in half and I don't think my little 110V MIG is the right tool for the job.
The few people I've talked to just seemed confused about what I was asking and that makes me a little uncomfortable. There's really only one shot at this so if they screw up I'm SOL.
Is it making noise in gear or out? Grinding in gear immediately makes me think of the synchros but it could be a number of things. If you end up needing anything I'll have an entire spare transmission and a spare gear set available
I thought it was probably the syncros too, it has 116k miles and I'm 99% sure it's the factory fluid, so I'm going to change it and see if it helps. What fluid do you recommend? The noise is in first and seconds gear and when it is idling in neutral with my foot off the clutch, it's not bad but it's loud enough to hear over my stupidly loud exhaust. That's good advice on getting another trans...hadn't really thought about it.
The noise at idle while in neutral sounds like a bad throw out bearing. As for gear oil I've had good experience with Redline MT90 although you may want to try something a little thicker like Lightweight Shockproof.
mymmeryloss
Member
- :
- 13bT Mazda B2600i
Im still checking in also but ive never done anything like this so im list. Just commenting on hear say and things of that matter.
Spent about 20 minutes in the garage all weekend. I spent most of my weekend cleaning the kitchen (yay!).
I did get the transmission fully torn down though. Just about every internal piece in one picture:
"Mostly" clean housings (still need a little scrubbing):
When I got everything torn down I discovered something neat about the Miata gear set. Second gear is double-synchro'd:
Note the second, inner synchro with the tabs. I'm not really sure what this means in terms of performance, strength, or reliability but it's interesting to note the little differences between the transmisisons. Aside from the obvious (bell housing and extension housing) there's a couple other small differences. For reasons unknown to me the oil cavities in the intermediate housing (what covers 5th/reverse) are different. The castings are the same but they're milled differently. Another interesting difference is the RX-7 reverse gear is straight-cut whereas the Miata is helical. Those are the most notable ones. There are several differences in snap rings, spacers, and the like.
Talking to another machine shop tonight about modifying the input shaft!
I did get the transmission fully torn down though. Just about every internal piece in one picture:
"Mostly" clean housings (still need a little scrubbing):
When I got everything torn down I discovered something neat about the Miata gear set. Second gear is double-synchro'd:
Note the second, inner synchro with the tabs. I'm not really sure what this means in terms of performance, strength, or reliability but it's interesting to note the little differences between the transmisisons. Aside from the obvious (bell housing and extension housing) there's a couple other small differences. For reasons unknown to me the oil cavities in the intermediate housing (what covers 5th/reverse) are different. The castings are the same but they're milled differently. Another interesting difference is the RX-7 reverse gear is straight-cut whereas the Miata is helical. Those are the most notable ones. There are several differences in snap rings, spacers, and the like.
Talking to another machine shop tonight about modifying the input shaft!
No pictures today; just a couple updates and a question.
Updates:
I dropped off the Miata input shaft and RX-8 rear stationary gear at a machine shop yesterday. I ended up getting referred to a machine/die shop a little further away. They seems to know what I was after although they're concerned the hardened input shaft may be difficult. In completely other news I got a call this morning from the freight company delivering my new fiberglass body parts. I'll be picking those up tomorrow afternoon. So excited!
Question:
Since I'll never go into 5th gear on track would it be worth it to swap my original RX-7 5th gear over to the Miata gear set? This will bump the ratio down from .814:1 to something like .75x:1 (Miata input shaft and countershaft increase the original RX-7 ratio from .697:1). I figure this might help make highway driving somewhat bearable.
Updates:
I dropped off the Miata input shaft and RX-8 rear stationary gear at a machine shop yesterday. I ended up getting referred to a machine/die shop a little further away. They seems to know what I was after although they're concerned the hardened input shaft may be difficult. In completely other news I got a call this morning from the freight company delivering my new fiberglass body parts. I'll be picking those up tomorrow afternoon. So excited!
Question:
Since I'll never go into 5th gear on track would it be worth it to swap my original RX-7 5th gear over to the Miata gear set? This will bump the ratio down from .814:1 to something like .75x:1 (Miata input shaft and countershaft increase the original RX-7 ratio from .697:1). I figure this might help make highway driving somewhat bearable.
Going with the lower gear would make sense if it will be used for highway, lower revs=better mpg's & slightly lower engine noise. Protege guys are starting to swap the 626 5th gear in for that reason. That's the extent of my transmission knowledge.
As far as 5th gear goes. I would be concerned with a lack of power on steep grades. Something you most likely won't encounter though. Other than that I say go for it, it will mean less stress on the engine at highway speed and better mileage as well.
He could always downshift
It ends up coming down between .814:1 or .750:1, which are both shorter than stock (.697:1). The difference is something like ~262 RPM (3334 RPM vs. 3072) at 70 MPH. The main goal would be to keep noise down so highway driving won't cause my ears to bleed.
I thought of this but with a 4.30:1 final drive ratio and 1:1 4th gear I'll be doing nearly 155 MPH at my target redline of 9000 RPM. Even with the increased horsepower and lighter weight I don't think I'll be hitting that at Mid-Ohio
.814:1 = 189 MPH theoretical top speed
.750:1 = 205 MPH theoretical top speed
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Machine shop called and said they're done; that was fast. Now I get to wait all day until I pick up my parts and confirm everything was done correctly. Even though I gave them a sheet with dimensions and instructions I'm still nervous something was done incorrectly.
I picked up the rear stationary gear and input shaft last night. Fortunately it looks like the machine shop guys did a good job (not like I should doubt a machine and die shop). Groove in rear stationary gear:
I'm not sure if I ever explained why this was needed. All rotaries seal the rear stationary gear with an o-ring. In RX-7's the o-ring sits in a groove in the stationary gear but in RX-8's it sits in a groove in the rear housing. Since I have a RX-7 rear housing and a RX-8 rear stationary gear I had no groove to speak of so one needed to be made. I wasn't able to get good measurements of the groove myself so I gave the shop my stock stationary gear to use as a setup. I plan on using a little RTV in addition to the o-ring so a little error shouldn't be that big of a deal.
And here's the input shaft. Fortunately it looks like the turned out correctly. Modified Miata input shaft on bottom, stock RX-7 on top:
A quick check shows the overall length and spline length to be a little longer than the RX-7 shaft but I verified the dimensions with Mazdatrix's recommendations and I trust they know what they're doing so everything should work. If not, there'll be hell to pay.
The fiberglass body parts were delivered yesterday too (busy day).
Shine Auto vented hood:
The hood is latched in above picture but not bolted to the car. It lines up fairly well but I'm going to have to lower the latch quite a bit it seems. It's a true vented hood:
I'll be tying the vent into some kind of post-radiator fan ducting eventually.
Shine Auto Fenders:
It's a pretty subtle flare but should be enough to cover the wider wheels and tires:
I've got family visiting this weekend so I won't be able to work on the car too much. The immediate plans are to reassemble the transmission and to mock up the body parts to verify fitment. I'll leave the final fitting and painting to the professionals. I'll be picking up a fender roller early next week to work on the rears.
I'm not sure if I ever explained why this was needed. All rotaries seal the rear stationary gear with an o-ring. In RX-7's the o-ring sits in a groove in the stationary gear but in RX-8's it sits in a groove in the rear housing. Since I have a RX-7 rear housing and a RX-8 rear stationary gear I had no groove to speak of so one needed to be made. I wasn't able to get good measurements of the groove myself so I gave the shop my stock stationary gear to use as a setup. I plan on using a little RTV in addition to the o-ring so a little error shouldn't be that big of a deal.
And here's the input shaft. Fortunately it looks like the turned out correctly. Modified Miata input shaft on bottom, stock RX-7 on top:
A quick check shows the overall length and spline length to be a little longer than the RX-7 shaft but I verified the dimensions with Mazdatrix's recommendations and I trust they know what they're doing so everything should work. If not, there'll be hell to pay.
The fiberglass body parts were delivered yesterday too (busy day).
Shine Auto vented hood:
The hood is latched in above picture but not bolted to the car. It lines up fairly well but I'm going to have to lower the latch quite a bit it seems. It's a true vented hood:
I'll be tying the vent into some kind of post-radiator fan ducting eventually.
Shine Auto Fenders:
It's a pretty subtle flare but should be enough to cover the wider wheels and tires:
I've got family visiting this weekend so I won't be able to work on the car too much. The immediate plans are to reassemble the transmission and to mock up the body parts to verify fitment. I'll leave the final fitting and painting to the professionals. I'll be picking up a fender roller early next week to work on the rears.
mymmeryloss
Member
- :
- 13bT Mazda B2600i
Coming along nicely!
