(Image Courtesy Ed Hartnett)The 1966 main instances observed some further design alterations. With the introduction of the 3885010 case, the countershaft bore was increased to one inch. The circumstance countershaft bore normally stretched out so the enhance in shaft diameter unfold the counter-shaft load about a wider area.
These two milled ) These transmissions almost certainly have been assembled with particular alloy gears, simply because the circumstance casting is identical to the 3851325 as well. Commonly when an external modification is manufactured to the scenario, such as milling, it means a exclusive internal mod.
This milled case https://plantidentification.biz/ from the selection-nine mould matches the unmilled scenario shown formerly with the exact same mould quantity and precise casting clock day code. What you can see is that before March 1965 these instances were not milled.
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(Picture Courtesy Ed Hartnett)This 3851325 situation, produced May 1964, shows a patent selection that’s equivalent to the PAT. PEND. circumstance. The 1965 variations of this case are identical besides that the upper middle extension housing bolt boss on the rear of the 1965 is sq. somewhat than spherical (proven) on the painted orange scenario. This scenario was made use of to the conclusion of 1967.
Later variations have a bigger forged pad on the rear of the passenger’s facet of the situation and thicker gussets on the mounting ears. The way to differentiate a 1966 3885010 situation from a 1967 is by the serial selection.
The early « 3851325 PAT. PEND » situation seems to be identical to the 3839609 but it is a a lot cleaner casting. This circumstance casting was used for the duration of the 1966 and 1967 design decades 1967 was the first time a calendar year designator was included to the serial amount. This just one has a January 19, 1967, day code.
This is a 1967 3885010 circumstance dated June two, 1967. The rear pad (exactly where the figures are stamped) is wider than previously variations of the scenario.
The mounting ears also have thicker gussets than before instances. This casting layout evolved into the 1968-and-up castings. The 3925660 instances have been utilised generally in 1968 to 1970. They look to be equivalent to the late 3885010 case with the broader « stamp » pad and thick ear gussets. Some places also have a lot more substance and the case has a thicker glimpse to it.
Perhaps an alloy alter as effectively as a tooling adjust warranted a new selection. By the begin of 1969 these circumstances and all long term cases experienced the drain plug boss drilled and threaded. The 3925661 casting appeared to surface by the final quarter of 1969. Stamped serial figures for all 1969 design yr instances also bundled the year designator.
1970 to 1974. The past Muncie situation was the 3925661. The « 661 » is thought of the strongest manufacturing facility GM case. It is similar to the 3925660 case but definitely has a distinctive colour. The situation seems to have a gray/eco-friendly hue and does not seem to stretch out like the older cases did. This 1968 3925660 most important case has a P8R04 assembly date and was forged in a number-2 mildew. The VIN in the left image is 28G107211 it decodes as Pontiac (2) calendar year 1968 (8) and G (plant) followed by the sequential production range.
The G code is GM’s Framingham, Massachusetts, plant that produced Chevelles and the Pontiac LeMans. Therefore, this is a LeMans scenario. Here is a uncommon 3925661 casting from a 1969 Camaro. The assembly date of P9P16A translates to September 16, 1969. The « A » stands for M20. Notice the odd casting clock over the fill plug and that it was drilled for a drain plug. This was mildew sample number 1. It was utilised principally with the 26-spline input shaft and larger 32-spline output-shaft designs, so it appears that they had been on the lookout to optimize strength just about everywhere doable considering the fact that the 454 motor was introduced in 1970.