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05-19-2017, 02:58 AM | #1 |
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Location: Liberty, MO
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Checking rear ratio
How do you check rear ratio without taking rear end apart thanks Richard
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05-19-2017, 05:44 AM | #2 |
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Re: Checking rear ratio
Mark the input shaft and the rear axle at a starting point. Then spin the input shaft 3 complete revolutions. If your axle spins about 1/2 of the way around probably have a 3.54. Larger ratios you might have to reduce that fraction..not precise but gets ya an idea
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05-19-2017, 06:07 AM | #3 |
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Re: Checking rear ratio
You asked the same question yesterday and got an answer.
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05-19-2017, 06:30 AM | #4 |
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Re: Checking rear ratio
Sorry Tom couldn't find how do you do it in the car
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05-19-2017, 06:41 AM | #5 |
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Re: Checking rear ratio
same thing as above but put the trans in 3rd gear jack up one wheel and turn the engine over 3 turns using the hand crank. 3rd gear is a 1:1 ratio.
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05-19-2017, 08:35 AM | #6 |
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Re: Checking rear ratio
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05-19-2017, 09:12 AM | #7 |
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Re: Checking rear ratio
Remember, with ONE wheel jacked up, the other wheel turns TWICE as FAST!!
In Auto Shop, even with cutaway rear ends, it took me a LONG time, to FIGGER thet one out???? It's because the AXLE gears have TWICE as many teeth as the SPIDER gears have! (Comprende'?) Bill Dummy
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05-19-2017, 09:40 AM | #8 |
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Re: Checking rear ratio
Sounds like a break down in communication here.
If all else fails, remove the rearend drain plug and drain oil. Remove filler plug and using a modelers paint brush, mark one tooth on the ring gear with white paint. Rotate one tire and count the number of teeth on the ring gear. Caution,,,,,,back tires must be off the ground to rotate. Report back with your teeth count. |
05-19-2017, 11:12 AM | #9 |
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Re: Checking rear ratio
Jack up only one rear wheel, put the tranny in high gear. Mark the tire and ground, then hand crank the engine. If you have to crank the engine just a little over 4 full turns to make the tire turn exactly 2 revs, then you have a 4.11 rear end ratio.
If you have to crank the engine 3 and 3/4 turns for two tire revs, then you have the 3.78 ratio. |
09-19-2017, 08:56 AM | #10 |
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Re: Checking rear ratio
Am I correct that I have a 4.11?
I did this check yesterday. 4-1/8 crank turns equaled 2 tire revs AND at 60 MPH I am doing 3,200 RPM. |
09-19-2017, 09:07 AM | #11 |
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Re: Checking rear ratio
Yep, sounds like you have the 4.11 ring and pinion. I can trade you a 3.78 for it if you want.
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09-19-2017, 09:43 AM | #12 |
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Re: Checking rear ratio
Thanks, I would really like to go lower. Anyone have any trades for a 3.54?
Last edited by old31; 09-19-2017 at 02:52 PM. |
10-12-2017, 01:34 PM | #13 |
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Re: Checking rear ratio
I have the engine out of the car and ran this test to double check my rear end ratio.
What does this tell you that I have. With the engine out I turned the left rear wheel 1 turn counter clockwise, with the trans in 3rd gear. The input shaft turned 1 full turn + an additional up to 7/8’s of a turn, it stopped just about at 11 o’clock. So, not quite 2 turns. With the wheel turned two times counterclockwise input shaft turns two and three-quarter turns Last edited by old31; 10-12-2017 at 03:43 PM. |
10-12-2017, 11:06 PM | #14 | |
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Re: Checking rear ratio
Quote:
Are you sure it wasn't 3 and 3/4 turns, which is the standard 3.78 ratio? |
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10-15-2017, 10:13 AM | #15 | |
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Re: Checking rear ratio
Quote:
With the engine out and trans in 3rd gear. 2 complete turns of the tire gave me 3 and 3/4 turns at the input shaft. In 1st gear it gave me 11 and 3/4 turns at the trans with 2 tire turns. |
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10-13-2017, 03:07 AM | #16 |
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Re: Checking rear ratio
I had the left rear wheel jacked up, the right rear was on the floor, and the trans was in 3rd.
Very possible that I miscounted, I will try again later today. |
10-13-2017, 04:31 AM | #17 |
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Re: Checking rear ratio
Here's the method I use:
Remove spark plugs Jack RH rear wheel just clear of the ground and mark the tyre at 12 O'Clock ( I use a spirit level to get it as close as I can) Set the hand brake so it is just dragging Select 3rd gear and direct drive if you have an overdrive Turn the engine exactly 2 turns. Now, if the mark on the tyre stops at 11-12 O'clock, you have 4.11 12-1 O'clock, you have 3.78 1-2 O'clock, you have 3.54
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10-13-2017, 07:33 AM | #18 |
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Re: Checking rear ratio
Clamp a vise grip onto the end of the input shaft with the transmission in 3rd gear and rotate the rear wheel that way. Perhaps a bit more precise.
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10-13-2017, 11:53 AM | #19 |
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Re: Checking rear ratio
Attached document may be of help.
Tom Endy |
10-14-2017, 04:50 AM | #20 | |
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Re: Checking rear ratio
Quote:
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