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Gearbox and Diff lube for Improved Touring Racecar

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Gearbox and Diff lube for Improved Touring Racecar

Old 03-27-19, 06:22 AM
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Gearbox and Diff lube for Improved Touring Racecar

Hello and greetings to fellow road racers. I would like to know what fellow SA22C Improved Touring A drivers are actually using in their 5 speed gearboxes and limited slip diff. I bought the car without having been able to talk to the last owner who actually campaigned the car in the South Atlantic Region SCCA so I have absolutely no idea what he used. Should I simply use the standard 75w90 oil GL4 as I have read in numerous threads? I'm not even sure what diff is on the car. What would you also recommend for the shifter turret? I have used Ford Unicorn Tears on the last shifter rebuild on my NA6 Miata but I suspect that the RX7 needs a different fluid. Thanks in advance.
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Old 03-27-19, 08:28 AM
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RX-7 gearbox is basically an older version of the Miata trans so the same fluid should be fine. We always used to run Redline Shockproof Lightweight; I don't know if it's the best or anything but ITA isn't the most demanding of applications anyway.
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Old 03-27-19, 11:29 AM
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Originally Posted by Kenku View Post
RX-7 gearbox is basically an older version of the Miata trans so the same fluid should be fine. We always used to run Redline Shockproof Lightweight; I don't know if it's the best or anything but ITA isn't the most demanding of applications anyway.
Couple of decades ago, I "pit crew" for a SCCA ITS FC3s. Everybody in that event was running Redline Shockproof. At the time, my street NA FC3s had a unsprung 6 puck bronze clutch; and I used to eat transmissions at a 1 per 2 years rate when using conventional fluid. After changing the fluid to Redline Shockproof, I was able to prolong the transmission life by 50% (at least).
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Old 03-27-19, 12:01 PM
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75w140 Amsoil in the trans and the rear end. Seemed to help with shifting later in the race when the trans was hot. Also, rear ends get really hot in these cars so I wouldn't using anything lighter than 75-140.
I also used a Center Force dual friction clutch with a sprung hub clutch disk because it was smoother.
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Old 04-23-19, 06:36 AM
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Thank you to all for the replies and the good information. I've replaced the gearbox oil but I am now unable to shift into reverse. I will take the shifter apart and take a look at what's going on inside. It was very sloppy when I first bought the car and it makes me miss the crisp short throws on my NA6 Miata. Perhaps it's high time for a shifter rebuild kit?
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Old 04-24-19, 08:25 PM
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Hello again, folks. Well, I took a look at the shifter. Aside from wear and needing a rebuild, I did not do anything to it. All I did was change the gearbox oil. I used 2 qts. Lucas Oil 75w90 GL4/GL5. As I posted earlier, reverse would occasionally be absent. Now after a test drive of 20 mins. 5th gear is out. I've tried shifting into 5th whilst coasting, I've tried double clutching, etc. Could all of these problems be caused by the gearbox oil that I've put in? Please help as I'm trying to get the car sorted out in order to attend Midwestern Council Driver's School at Blackhawk Farms this Friday.

Last edited by mikevillena; 04-24-19 at 08:29 PM.
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