Looking for pinion offset measurement on 9". The amount of pinion from dead center. Thanks in advance.
I believe it would depend on the vehicle the rearend came from...theres a fair bit of variation...unless you have an empty housing and are just looking for the offset that is built into the pumpkin. I'd suggest having a pumpkin on hand at least...just to make it easier to visualize pinion angle etc during setup, if thats the reason.
I think there is a formula for computing pinion offset, but I can't recall what it is. Here's some opinions. http://www.pro-touring.com/forum/archive/index.php/t-2302.html
I wanted to find the pinion offset on a 1971-73 Ford Tracl Loc 9 inch (28 spline, small bearing) rear and was told to do this: Subtract the total length of the Driver side axle (27.8125") from the total length of the Pasenger side axle( 31.875"). That difference is 4.0625". Then, subtract 4.0625 from 4.375 which gives .3125". Then divide .3125 by 2, giving .156". However, that .156 seems pretty small AND I do not know where the number 4.375 comes from. Is it a constant or is it a measurement that represents a compont of the rear, like the pinion or ring gear? Therefore , I would like to know if this is a true formula for computing pinion offset. Any input is appreciated.
Here the info: Read steps 3,4, 5 under Instructions www.tcp-racing.com/download/instructions/916716.pdf PLUS, Here is where the number 4.375 comes from: http://www.tavia.com/05001_instructions.html If anyobne can explain this clearly in laymans terms, I sure would appreciate it. That 4.375 number confuses me. thanx
Just in case the above links don't work, here's the summary: Note: Stock 1965-70 Mustang housings will have a centered pinion. INSTRUCTIONS f for measuring pinion offset You must determine pinion location in relation to the axle housing ends. 1. Place a carpenter’s square or straight edge against the driver-side housing end so it extends forward for easier measurement. 2. Measure from the driver-side housing end (carpenter’s square) to the pinion centerline and record this dimension. 3. Repeat measurement steps for the p***enger side. If both measurements are equal, the pinion has zero offset. If there is a one-inch difference in measurement, the pinion has a 1/2” offset to the p***enger side. 4. Make note of the pinion offset, and then remove the third member from the rearend housing.
19Fordy, The 4.375 number (for a 9" Ford) is referred to as the: Master Housing Dimension and probably a ton of other terms - I've not heard or couldn't remember. All different terms for the same thing. What it is is simply this: It is the THEORETICAL distance from the CENTER of the Ring Gear to a Reference point on the Pinion Gear. When the factory (or aftermarket) manufactures a set of gears - they are subject to tolerances. If life was perfect you could simply adjust your pinion depth to this setting - adjust for side to side and have a PERFECT pattern. Instead the manufacturer will set up the pattern, measure their error and TELL US by marking it +.003" or -.001" (or just +1 or -2) which we then add/subtract from the Master Dimension and get the reccomended installation height. For example: knowing that ideally we want 4.375" but our gear is marked +.003" we now know that when we set it up that we can put it at (4.375+.003=4.378") 4.378" or if our gear was marked -.001" then we'd adjust it to 4.374". Lots of guys just skip this step and shotgun it. I find that you save yourself a lot of grief by starting off setting the pinion to the depth the factory reccomends and then make your side to side adjustments. However - the pattern is the REAL check - numbers are there for reference - but if a dufus employee writes the wrong number or as I had happen to me their writing was so sloppy I set mine up at .007" instead of the .001" it was supposed to be. Lucky for me I caught it. You get a warm fuzzy feelign when both the Checking Distance numbers and the pattern are both "happy". Edit: I think the confusion in the Master Housign Dimension is that part that it is referencing the pinion's rear bearing face to the ring gear centerline. Problem being that THOSE surfaces are pretty tough to measure when you've got teh pinion installed. So the dimension that EASY to measure is from the END of the pinion to the ring gear centerline - this is called the CHECKING DISTANCE. To drone on further IF you would measure the distance from the END of the pinion gear to the Pinion rear bearing face and SUBTRACT that from the Master Housing Dimension - you'd end up with the Checking Distance. 2nd attempt to convert to layman's terms. The 4.375" dimension is the dimension used to set the pinion depth - but it references surfaces not easy to get to so we subtract the Pinion Head depth to get to a place we can actually measure to. I think a picture would be worth a thousand words here. I'll try and dig one up....... EDIT #2 http://72.14.205.104/search?q=cache...stance+9%22+ford&hl=en&ct=clnk&cd=3&gl=us Not sure if I succeeded - but I tried. BTW - The "Pinion Offset" number (.94") is the physical distance that the pinion is offset from the CENTER of the CASE. You can machine the axles/housing to then place the pinion anywhere you want RELATIVE to the HOUSING (centered, offset)
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