What happens in a transmission rebuild - Part 7

[Mac VP]

LINK TO ORIGINAL POST:
https://www.fordbarn.com/forum/showthread.php?t=278347

PLEASE NOTE: Part 7 has two groups of text and images. Be sure to scroll down for the second part.

Many steps occur in dealing with the mainshaft. After cleaning and inspection, we usually test fit the various gears that are associated with its assembly. If we are re-using the same gears from the core unit, they generally fit correctly since they had already lived there. If replacing any gears, be sure to test fit them.

The next step is to install the rear (or as known in overdrive transmissions - the intermediate) ball bearing. This bearing originally was specified without a snap ring groove, however in service the same bearing with the groove is often used. Since the original bearing had no groove, it doesn't matter which direction you fit the bearing to the shaft. The inner race of the bearing should be a light press fit to the journal of the shaft. If you find that the bearing slides all the way into place by hand, we suggest dimpling the shaft bearing journal (4 to 6 dimples with a sharp punch) to provide enough friction to keep the inner race from spinning on the shaft. A snap ring is then placed behind the bearing.

The bearing and mainshaft can then be fitted to the overdrive adapter casting. The special oil baffle must be dropped into the pocket first (beveled cup side out toward the rear). Then the shaft and bearing are fitted into place. Make sure the pocket is clean and lightly oiled. You often have to tap the shaft and bearing down to seat the bearing all the way into place. The snap ring groove should be visible just above the front of the bearing outer race. The retaining snap ring must be compressed slightly to fit it into the groove.....make sure it has seated properly.

[Mac VP]

LINK TO ORIGINAL POST:
https://www.fordbarn.com/forum/showthread.php?t=278347

This is the second part of the PART 7 thread. Now that the mainshaft has been installed into the overdrive adapter casting, we can begin the assembly of the gears and synchronizer to the shaft.

The low-reverse sliding gear goes on first.....with the shift fork groove toward the rear. As a side note, all Ford designed 3 speed transmissions were made to keep the fork groove to the rear for this slider gear. When Ford began to buy complete overdrive transmissions from Borg Warner (ie the T-86 model) this gear was fitted with the fork groove to the front.

Next you slide on the 2nd gear (intermediate gear) as shown. It will ride up against the 16 spiral splines of the mainshaft. The synchronizer assembly will slide on next, and locate up against the front of 2nd gear. This will place the front snout of the synchro hub even with the snap ring groove on the mainshaft. When the snap ring is placed in this groove, you can test for the endplay of 2nd gear. Tapping the gear and synchro assy forward against the snap ring, you want to see 0.004 to 0.008" of clearance behind 2nd gear.

At this point, the 2nd gear bronze synchro ring is in this stack of parts. The 3rd gear (high gear) synchro ring is still loose and not ready to be installed yet.

Be sure to place the small 7063 spacer ring onto the front of the mainshaft pilot (all the way toward the shoulder where the six splines begin). The 1949-50 Mercury transmissions had the small/long pilot on the mainshaft because they were fitted with the B-7118 caged roller bearing there. The later transmissions did not use this spacer ring, and were fitted with the loose roller needles for the pilot.

[Floyd]

Always good stuff if MacVP is involved.
It cannot be emphasized too much about the second gear clearance. This IS the major reason for the dreaded "slipping out of second gear" problem that everyone is aware of. Note that the spec is 0.004 to 0.008 from Ford. Also note that in the above picture, Mac says that it should be 0.004 to 0.006", (with a new gear/shaft/washer). I totally agree with this. When I get 0.0055", I am very happy. This is very important. You really want to be in 0.004 to 0.006" range. Measure, measure, measure, take it apart and put it back together again and measure ,measure, measure. This IS the area where a couple of thousandths of an inch make a big difference between Good and Not Good.
What happens if you don't get the sweet spot, 0.004 to 0.006?
That depends on the year range of the transmission. A subject for a write up by itself.
Now back to the professor, MacVP

[51woodie]

Nice presentation, and the description and pictures make it easy to understand, for someone like me who has never had the opportunity to rebuild one of these unit. However, I am a bit confused where the article gives a spacing of .004" to .008", where as the picture shows .050" to .060" gap. Is the .004" to .008" space to be measured between the back face of the second gear and the shoulder of the shaft where the splines start, when all the parts are pushed ahead?

[Mac VP]

The endplay measurement refers to the small clearance behind second gear when the synchro assembly and its retaining snap ring are installed on the mainshaft. You would slip a feeler gauge between the back face of second gear and the beginning shoulder of the spiral spline part of the shaft.

The other measurement relates to the fit of the bronze synchro ring onto the tapered cone of second gear. This is not a reference to end play.

[51woodie]

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Thank you Mac. I kind of figured that, but having limited experience, I wanted to be sure. Having worked on other transmissions, I understand the need for the clearance on the synchronizing ring.

[JM 35 Sedan]

Thanks again Mac! These transmission tech presentations you're doing are awesome!

A friend and I rebuilt the original transmission in my '35 fordor sedan (Avatar) last summer, using the original '35-'36, #48-7005 case, a nice set of side loader '40-'48 gears, with a 29 tooth cluster gear, the later front bearing retainer w/lip seal, the original shift top, w/slant back tower, and a special set of shift forks made from various other top & side load fork assemblies, all Tig welder together. During assembly of the gears into case, we took special care to get that 0.004" - 0.008" spacing tolerance set to just a bit below the midpoint of that spec.
I have to say this transmission shifts so nicely now, and is a huge improvement over the original gear design, and no matter what I do now while in 2nd gear, it will not pop out of gear as it did with the original gears!! The combination of this transmission modification, with a 3.54:1 rear gear ratio, makes this an amazing open road touring car.

[tubman]

After reading this, I am realizing how lucky I was with the '39 top-loader with later gears I put together (can't really say "built") about 25 years ago. I cleaned everything up, used the best parts I had with new synchronizers, gaskets, and bearings and it ended up great. Shifted smoothly and I never broke it with the 276" Merc I had in the car.

I think this is more a reflection on the quality of Ford's parts and manufacturing procedures than my skill as a transmission technician.

Thanks for this thread, Mac. I promise to do better next time.