So the results are in. It turns out that for me that it really doesn't make any difference. 2.47, 2.65, 2.82 all perform the same in the 1/4 mile. Reason is the limiting factor is traction. The best times no mater what gear ratio always occurred with the very large MT drag radials which I no longer have. Today I ran on Nitto Street radials. Best time was the first run of the day at 13.575, corrected to 13.637.

Compared to last year with the 2.47 gears and MT drag radials where I ran corrected to 13.502 at the same track.

I'm sure a stock 560SL could take advantage of it but the wheel and tire combinations that fit into the 560SL without modifications just cant take advantage of it, but I'm sure a seasoned driver could handle it much better.

One of the things I noticed with this gear ratio was that I not only had to worry about spinning the tires off the line but twice today they got away from me about 50 to 100 ft down the track.

There is no reasone for me to run any more 1/4 miles until I can get my 60' times under 2 seconds.

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To see my 129 parts for sale visit:
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John Roncallo

I had a old mazda truck,with the good timing chain engine and manual trans.I thought I'd use jiffy lube,and have them change my trans fluid.I warned them before hand use 80-90 wt oil. Got my truck and for 2 weeks it hauled butt,faster,then trans got louder. Then stuck in gear.They had put ATF in it,like new ranger/ mazda's. Had to find a trans,as it was ruint,replaced output bearing but junk inside trans.

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1999 w140, quit voting to old, and to old to fight, a god damned veteran

OK, I don't know what this has to do with gear ratio performance, but since we are off topic talking about people screwing up Mazda transmissions, Its now time for a story.

About 15 years ago I was learning to fly helicopters. I arrived one day for a lesson. As usual I start my pre flight and start the helicopter. The instructor comes out and buckles in and just as I'm about to pull collective and get off the pad, he says "You know about cars right". I said yes what was the problem, knowing I was about to get sucked in to a tale of woe while I had a rotor spinning at $225/hr. So he explained that he changed his engine oil was driving it and all was well then it started to slow down and finally stopped. He told me he could start it and it ran fine but as soon as he let out the clutch it would immediately stop. He also told me he checked the oil and it was very high.

So the picture fell together very quickly for me and I had to break it to him that he did indeed drain the transmission and filled the engine and consequently drove the transmission to destruction and would now need a new transmission. As I'm telling him this, all I could think of was "And now this guy is going to teach me how to fly the most complex piece of machinery ever concocted by man."

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John Roncallo

Got back to the track today. This time I did my burnouts correctly. Today Samson did its best ever 1/4 mile time at 13.342 @ 107.30 MPH. It was cold so that corrects to 13.426 @ 106.641 MPH. Still the Achilles heal for this car is the 60 ft time of 2.137 seconds. I was running Nitto P245/50R16 Street radials at 20 PSI. I'm not sure if its me or could a good driver get that 60' time below 2 sec with these tires. Best 60 ft time to date has been with Riken Raptor 275 35 R18, running 2.051 sec 60 ft time. I was also running with a 2.65 ratio.

So the conclusion is that without tires to take advantage of the 2.82 gear set. The change is a wast at least for the 1/4 mile. Tiny decrease in ET larger reduction in gas mileage. For a track car the advantages would be a little better. It does appear noticeable coming out of corners.

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John Roncallo

Here's something I found:
"Thanks to Carl at BergWerks, the 2.82 diff swap went well. I haven't picked up the car yet (this week) so I can only go by the numbers he gave me.

Pre-swap 0-60 times was 7.1 seconds. Post times were 6.5 seconds. Turns out that I had a broken kickdown switch. Not sure how (or if) the switch fix will change the times."

400E going from 2.24 to 2.82 gears.
400E differential

That's the kind of info I was looking for thanks. I don't have a good way of measuring 0-60 but I can calculate it based on 1/4 mile data. I picked up about a 1/2 second in 0-60. But the calculation are prone to integration error. 5.5sec to 5.0sec going from 2.47 to 2.82.

I would love to see more comparisons like this, preferably with 1/4 mile data.

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To see my 129 parts for sale visit:
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John Roncallo

Have you weighed the completed car?

Here's the data. I should do this again as it now has AC and a lighter weight rear subframe and diff.

M117 to M120 Weight Impact

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To see my 129 parts for sale visit:
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John Roncallo