Rear end Gears?

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Apr 17, 2012 | 11:14 AM

73 454

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From: Central Iowa

Rear end Gears?

How do i know what rear end gears are in my car? Is it coded in the VIN or located on the car somewhere?

thanks!

Apr 17, 2012 | 11:22 AM

Mike Ward

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It's stamped on the bottom of the diff housing or listed on the tank sticker. Many diffs have been swapped over the years so it's possible that the present ratio is not the original.

Turn the driveshaft and see how many turns it takes to cause the rears wheels to turn once. That's the ratio.

Better yet, just get the M20 gearbox irrespective of what ratio you've got.

Apr 17, 2012 | 11:23 AM

MelWff

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Jack the back of the car off the ground and support it with jack stands. Place the vehicle in neutral with parking brake off. Place a chalk or crayon mark on the driveshaft. Turn one of the rear wheels one complete turn and note how many times the chalk mark goes around. If the driveshaft turns a hair more than 3 turns you have a 3.08, 3 1/2 turns a 3:55, 3 3/4 turns a 3.70, etc.

Apr 17, 2012 | 11:42 AM

73 454

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From: Central Iowa

I just need to know what trans i should get to handle the power i'm making. I'm getting the itch real bad! The weather's getting nice out and i don't have a vette to drive

A shop i talked to told me to get the M22 and you guys on here are telling me to save the money and get a M21/M20 combo because they'll hold the power.

The shop also asked me what rear end gear i have to determine the best trans for my car.

Apr 17, 2012 | 11:57 AM

MelWff

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I guess your mixing threads because all you asked is how to determine the rear end ratio. I dont see how you can determine what transmission you need based on a rear end ratio. The engine is a key factor in determining what to do. The M22 was intended for high horsepower vehicles that were primarily going to be raced. They tend to be noisier because of the way the gears are cut. You have to provide more information if you are looking for an answer. Tell us about the engine, tell us what you primarily want to do with the car?

Apr 17, 2012 | 12:03 PM

Mike Ward

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Quote:

Originally Posted by 73 454

I just need to know what trans i should get to handle the power i'm making.

Did anybody suggest getting the M20?

Apr 17, 2012 | 12:18 PM

73 454

Thread Starter

Instructor

Joined: Jun 2008

Posts: 173

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From: Central Iowa

A few members on here memtioned the M20 yes. Although i'm not sure the diff between the M20/M21. My stock trans was the M21 Code B for close ratio.

My engine is a 454 with electric water pump/cooling fan. Stock heads with mild port job just to clean them up. Long tube headers And a decent/mild cam with a nice sound to it

So i'm guessing maybe 500/500ish fly wheel.

The car is just going to be taken to local shows and cruised on nice weather days with the occasional run through the gears.

I really did a number to the internals of the trans. The main housing has a good sized "ding/chip/chunk" missing out of where the tail shaft housing bolts up to it.

So my dilemma is to get a new main houseing and all new gears for it and have it rebuilt or just buy a whole new trans and put it in and be done with it.

Sorry for the confussion with the theards