Re: 4.10 gears...not what I expected.
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Yikes! "If you can't explain it simply, you don't understand it well enough." - Albert Einstein (This discussion has veered off-topic, but since we're here now...) Ratios. No matter how you slice it, the root to questions regarding the effect on differential gears, speed, rpm, or any other equivalents resides in the ratio of one tire size to the other. Period. Depending on the question, there may be a direct ratio relationship, or an inverse (i.e, 1/ratio) relationship, but regardless, that ratio between tire sizes permeates all calculations regarding differences in gear ratios, or distance covered per tire rotation, or rpm, or you name it. For example: If speed over the ground and engine rpm are to remain constant, then the differential reduction ratio (ring/pinion) must be changed by the same ratio as that between the two tires. Otherwise, either speed over the ground will change for a given motor RPM, or RPM will change for a given speed. Or, for an opposite example, to find the equivalent differential reduction ratio value resulting from a change of tire size, the inverse (1/RATIO) x differential reduction gear ratio will produce the effective equivalent rear end gear ratio (as well as the ratio correction required for the new speedo gear. And, so it goes... (Well, almost. Practical applications typically have dynamic variables which skew results. Variables like Hog points out and many other practical bits and pieces get in to increase the ambiguity factor. But, as long as we can account for some of of the small dribbs and drabbs, and the ambiguity doesn't exceed say 5%, it should suffice for purpose of discussion, I should think.) Hog: Good points as well. But back to the OP's question: What are the real trade-offs between say the 4.10s vs. stock 3.45s in actual driving or racing situations?? :cheers: WV: I must be staring right at it but do not see: where is that "336" factor you use in your calc's derived from? |
Re: 4.10 gears...not what I expected.
Dave,
Actually we had a very similar thread several years ago here for anyone interested in referring back to it. http://zr1.net/forum/showthread.php?...ear+axle+ratio And I in fact did what you suggested, which was to use the stock 3.45 trans gear With the 3.73 rear gear. Based on my GPS v Speedo, I get ~ 4% error! with the speedo reading slower. Good enough for cruising. Some of the specs are in that thread. |
Re: 4.10 gears...not what I expected.
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I've used the 336 number for years and I don't know where I got the formula for it originally but there's explanations and the formula scattered about of all places "The Internet". I found this explanation since you asked your question and it seems pretty concise and easily understood too, I'll just post the link. I believe it should work. Regarding explaining it 'simply'? I thought I did. Understanding it? Yes I do. There are calculators that are used by many that aren't accurate and I just displayed my math, that doesn't have anything to do with understanding or simply. There are some RPM/MPH charts in this thread and all use 'advertised' tire specifications and not a 'loaded radius' it appears. I couldn't make the numbers match unless I used the 'advertised' dimensions. http://www.numericana.com/answer/formula.htm#carspeed |
Re: 4.10 gears...not what I expected.
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I did speedometer calibrations for people to take to court and attempt to get fines and charges reduced to improper equipment etc. back in the day. I had to 'introduce' the error that we're attempting to correct these days. I don't recall any of my calibrations failing the person except a couple occasions where the person asked for an error that just wasn't likely accomplished. I did the calibration, the buyer went to an approved certification station and of course there was an error, the person reinstalled the correct parts OR we actually corrected the error, the person returned to the certification station they certified the correction and the receipt for services went to court. Charges usually dismissed, occasionally if the JP/Judge suspected the tampering there was an improper equipment citation issued which had no points and a very low fine. All the math was done on paper and changes sometimes by trial and error. |
Re: 4.10 gears...not what I expected.
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I did go from the stock 17' A molds to an 18" Shelby but I made sure the overall diameter was the same (or at least very close). I've always assumed that was a determining factor. I guess I was right... |
Re: 4.10 gears...not what I expected.
Our testing, years ago, with a modified ZF trans gears (to keep the drop between shifts in the engines peak power band) and with higher horsepower engines the 391 ratio was the one that got to the finish line first.
We attempted to get the trans ratios to where we had five gears instead of 4 plus 2 overdrives, that worked real well. REEEEEEAL EXPENSIVE Look up Gforce and look at the transmission ratios Leo makes for an example of what can be done to the ZF it money is no problem. |
Re: 4.10 gears...not what I expected.
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Did that test include stock 375 or 405 hp or (??) cars? Paul. |
Re: 4.10 gears...not what I expected.
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No I "hacked up" everything and motor I played with, christ my lt1 70 car (350-370hp stock) had a 425 hp small block so I thought the lt5 GM hp numbers were pathetic, the 650 number Lotus had made me curious. We just never cut a hood open inorder to straighten out the intake air flow to get to their numbers. Did everything else, though. |
Re: 4.10 gears...not what I expected.
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Re: 4.10 gears...not what I expected.
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We always started with baseline runs to see how much GM fudged the numbers for insurance purposes. Common practice... So I would call those numbers for both engines net at the flywheels. When the ZR1s were introduced the LT5 option alone was $35,000.00 and there were no aftermarket engine parts for the LT5. I still have one of the first sets of JLs lightweight pistons in my cabinet. I have I believe 2 different sets of cams because we were testing for max lift limits/spring pressure ranges. Airflow was always the restriction that limited the output. When I started fooling around with them Lingenfelter charged $16,000 to build a motor from a new engine and Calloway was at $14,500.00. Now guys buy their entire cars for that. I always wonder how many of the current owners would have one, then try and modify it, if they had to pay 80K for them. even in the lower current usds. |
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