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Toploader Transmission Tips

photos provided by Robert Dolson

A common problem with most BOSS 302 owners is they don't know what type of Toploader 4 speed transmission (trans.) they have. Whether it's a code 5 - Wide ratio or a code 6 - Close ratio. We can only guess based on what we see with the registry. It appears to us that most 3.50 rear ratio cars got the Wide ratio trans. because the higher rear gear needs the lower 1st gear to be able to pull out better. Most 3.91 cars got the Close ratio, for what we believe to be a good road race set-up, for less RPM drop. Most 4.30 cars got the Wide ratio for obvious drag race qualities. This is only our opinion of what FORD seemed to be doing. We may be wrong.
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1970 BOSS 302 Toploader transmission with Hurst Shifter (above and below)

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If you want to know what type of trans. you have for sure, here are some tips.

In Car or out of car - Look for a small metal tag attached to the transmission. On the tag you should find one of the following codes:

1969 - RUG E3 = Wide ratio

1969 - RUG AG = Close ratio

1970 - RUG AV = Wide ratio

1970 - RUG AW = Close ratio

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Trans. out of car and no tag - 1) Remove lid of trans, if the input gear is smaller than the input bearing, it is a Wide ratio. If they are the same size, it is a Close. 2) Remove the bearing retainer. If it has a groove on the input shaft it is a Wide, if not, then it is a Close. 3) Put the trans in first gear. While turning the input shaft, count the number of turns it takes to complete one turn of the output shaft. If it takes approximately 2-3/4 input shaft turns then the trans is a Wide ratio (2.78:1). If it takes approximately   2-1/3 input shaft turns then the trans is a Close ratio (2.32:1).

In Car, no tag - Jack rear wheels off ground, run engine to normal operating temperature. Put trans. in first gear and let idle steadily, write down speed. Put trans. in 4th gear and let idle steadily, write down speed. Divide 4th gear speed by 1st gear speed. The result equals the ratio.

Another method is just about the same except drive the car out on a flat road and again record the idle speeds in 1st and 4th gears and divide. A tach can also be used by picking an exact rpm.

2.78 is a Wide ratio and 2.32 is a Close ratio.


What else should you be looking for on a BOSS 302 Toploader trans? One thing to look for is the vehicle identification number (V.I.N.). Part of the V.I.N. was supposed to be (Nothing is 100% for sure when we are talking about humans stamping parts. And nothing on service parts.) stamped on the top left of the case. Typically we find the first two digits like "0F" and then the last six digits "123456" or sometimes just the last six. So it would look like "0F123456" or "123456". In this photo you can see how things don't always turn out as planned. You can read "0T" but not much else beyond that. Keep in mind this is just one example. We have seen many with better stampings.

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What else? Here is a close up of the case. Note the part number.
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Tailshaft housing.
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Input shaft.
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If you are looking at a 1970 to be original you will need a Hurst shifter.
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This page last updated: January 02, 2015