[C2] Bang and Crunch Sound
07-04-2019, 04:52 PM
#61
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07-04-2019, 05:46 PM
#62
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Suggest having the transmission shop determine your rear ratio and also the transmission gear set (WR or CR). Locking it in first gear it will either take 2.2 turns of the input for 1 turn of the output (CR) or 2.5 turns of the input for 1 turn of the output (WR). If you really have a CR and 3.36 or higher rear, a wide ratio as suggested by others is probably a good choice. If your "big" engine is not too badly cammed (maybe a hydraulic roller?) and has good torque you can get by with a CR and 3.31 gears but around town it will take more than normal clutch slipping and care in getting away from a stop.
If you decide to invest some money in the transmission and build a WR one, I would recommend the Autogear M22W (wide ratio). The gears are made in Italy and are really nice.
I sort of splurged and used a new Autogear Supercase also.
Without looking up my invoice I think my parts bill for new case, rebuilt kit, new gear set, new bearing retainer, etc was around $1200. I worked with Larry at D&L Transmissions and he recommended re-using my tailhousing, mid-plate and side plate as long as they were in good condition. The Autogear tailhousing is noticeably bulkier and he said had been a little bit of an issue with Corvette tight tunnel clearances. It seemed like he said he had seen some issues with the billet mid-plates by Autogear but I know Paul's 5-speeds has developed a billet mid-plate also, and it looked really nice if one is needed. They are probably not an issue now.
If you decide to invest some money in the transmission and build a WR one, I would recommend the Autogear M22W (wide ratio). The gears are made in Italy and are really nice.
I sort of splurged and used a new Autogear Supercase also.
Without looking up my invoice I think my parts bill for new case, rebuilt kit, new gear set, new bearing retainer, etc was around $1200. I worked with Larry at D&L Transmissions and he recommended re-using my tailhousing, mid-plate and side plate as long as they were in good condition. The Autogear tailhousing is noticeably bulkier and he said had been a little bit of an issue with Corvette tight tunnel clearances. It seemed like he said he had seen some issues with the billet mid-plates by Autogear but I know Paul's 5-speeds has developed a billet mid-plate also, and it looked really nice if one is needed. They are probably not an issue now.
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07-11-2019, 08:57 PM
#63
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Okay, finally heard back from the transmission rebuilder. It is a close ratio and most of the parts are toast. He said he could turn it into a wide ratio, no extra cost, so I told him to go ahead. Going to be $1400 for the tranny, $600 uninstall/install.
My questions to you guys are, is there anything else different between the M20 & M21? How about the side case? Shifter linkage? Etc.?
My questions to you guys are, is there anything else different between the M20 & M21? How about the side case? Shifter linkage? Etc.?
07-11-2019, 09:02 PM
#64
Le Mans Master
Let him fix what you have with the wide ratio change, I think you will be quite happy with that option especially on the highway. 
Last edited by Pilot Dan; 07-11-2019 at 09:04 PM.
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07-12-2019, 07:05 AM
#66
Race Director
Okay, finally heard back from the transmission rebuilder. It is a close ratio and most of the parts are toast. He said he could turn it into a wide ratio, no extra cost, so I told him to go ahead. Going to be $1400 for the tranny, $600 uninstall/install.
My questions to you guys are, is there anything else different between the M20 & M21? How about the side case? Shifter linkage? Etc.?
My questions to you guys are, is there anything else different between the M20 & M21? How about the side case? Shifter linkage? Etc.?
There are also China (Korea??) gear sets around but with the Italian ones available I was told to avoid them.
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59BlueSilver (07-12-2019)
07-12-2019, 01:09 PM
#67
Le Mans Master
Don,
He mentions in post #52 that he has a 3.08 or 3.36 rear in the car which is a nice combo with the wide ratio tranny if you cruise on the highway. The wide ratio makes for better overall driveability with the low rear going through the gears IMO.
He mentions in post #52 that he has a 3.08 or 3.36 rear in the car which is a nice combo with the wide ratio tranny if you cruise on the highway. The wide ratio makes for better overall driveability with the low rear going through the gears IMO.
07-14-2019, 07:36 AM
#68
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Another question, changing over to a wide ratio, how does that affect my speedometer readings? Before I was going 5mph faster than the speedometer showed.
07-14-2019, 07:37 AM
#69
Instructor
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07-14-2019, 11:38 AM
#71
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As stated, not at all. You will still be going 5 mph faster than the speedometer shows if you make no changes to the speedometer driven gear. All stock 4 speeds have a 1:1 4th gear. So all will read the same MPH. What affects speedometer accuracy is final drive ratio of the rear end and rear tire diameter. I'm betting with your car indicating 5 mph slow, that you have tires about an inch taller than stock, or the wrong driven gear.
07-14-2019, 01:51 PM
#72
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I’m running 215/70R-15 (26.9 dia.) so should be compatible. Someone must have changed the gear. What color should it be, blue?
07-14-2019, 09:11 PM
#73
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07-20-2019, 07:36 AM
#74
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After almost two weeks, I finally got my car back with the rebuilt transmission. Runs great, shifts good, a little stiff perhaps, but that’s normal for new parts. Love that wide ratio, getting out of the hole is a lot easier now.
Gave him a bag of nylon gears to change out the speedometer. All mine are small diameter and, of course, the tranny requires a large gear, which they don’t make. I need a 21 tooth large gear. I wish I had changed out the worm gear to match my bag of small gears. Oh, well...
Gave him a bag of nylon gears to change out the speedometer. All mine are small diameter and, of course, the tranny requires a large gear, which they don’t make. I need a 21 tooth large gear. I wish I had changed out the worm gear to match my bag of small gears. Oh, well...
07-20-2019, 02:19 PM
#75
Race Director
Good deal - thanks for letting us know.