Thanks Andy. Yes I’ve been pencilled in for spring.
Planning this as a winter project on my 69 Vert (351W FMX, 3.25 TrueTrack). To take the mystery and worry out of it I’m going with LenTech’s street cruiser with a tighter 1st and 2nd gear set and 1800-2200 stall converter. It might be a bit more expensive but doing the install yourself should help keep the costs down.
I’m not trying to hijack this thread but I also own a 1967 Mustang GTA. It has a 5 liter crate motor (345 HP) with fuel injection, 2500 rpm stall convertor, AOD and a 9-inch with Auburn True-Track posi and 4.11 gears. This is my daily driver and I commute between Phoenix and Tucson once per week. I usually take Hwy 79 which goes north from Tucson, through Florence, AZ and dumps onto Hwy 60 near Florence Junction, AZ. From there I go west until the hwy turns freeway and I get to my office. I prefer going the back way as the speed limit is 65 and that is right at 2700 RPM for me (besides there are Way-y-y-y fewer cars).
I’m here to ask if anyone has done a gear swap in their cars using Motive Gear sets. I have them in my 67 and there is always a slight whine under accel or decel. I rebuilt the rear-end a few years ago and it is neither louder now or quieter now, still the same. I also did the rear-end in the 70 Cougar with 3.50 ratio and a locker (not Auburn but the other one). I have not yet driven the car but I adjusted the gears on the 3.50 pumpkin about 20 times to be sure I had it right. I did the same procedure as I did on the 4.11. My concern is that maybe something was not quite right with the way I did it. If Motive Gears (4.11:1) are known to make some noise then I’m good, otherwise I may redo both of them.
Here are some pics of the tooth pattern I did when I rebuilt the 4.11 set…
4.11 View “A”
4.11 View “B”
We also entered a pumpkin carving contest! My entry is on the left…
I did not win the contest, but at least there was no whining about it!
Chuck
Ooops, I guess I do not have any of the 70 Cougar pumpkin, that I can find anyway.
The pattern looks good, but most times the whine comes from the bearing preload, the pinion bearings mostly.
Too tight or too lose on the pinion bearings? That would indicate a preload set incorrectly.
I’m not as experienced in differentials but been reading up lately. One basic source of noise is the gear tooth combinations. In the case of a 9" the 4.11:1 is an ideal set whereas the 3.50:1 ratio as a “common factor of 5”. I guess this means multiple teeth contacting simultaneously. So the fact that they both make noise makes me think it’s not related to the gears themselves but another area. Perhaps what Catlover was suggesting.
Common factor of 5 means that every 5th revolution, the same teeth are meshing.
Your contact pattern looks ideal. I’ve installed a few Motive Gear and some just won’t run silent. They do seem quieter than Richmond.
I haven’t heard of pinion bearings making noise when in good shape and properly adjusted… Worn or loose bearings will be the cause of noise.
Maybe I’ll pull it and recheck everything. I recently built a 31-spline unit for the Cougar. 3.50 Gears and Eaton locking posi. I had the gear sets out and back in probably 35 times before I was happy with the pattern and preload. I’m getting pretty good at setting them up now. I have not yet run the Cougar as the engine/trans is scheduled to be reinstalled on Tuesday, Nov 23, 2021. Then we’ll give it the old “smoke test”.
I actually just got my 3rd member back with motive gears in it. Went from a 3.00 to 3.89, and got an eaton trutrac in there. I went with the Motive set as it seemed that most people had no noise, however I must have gotten unlucky or something since I’ve got whine on deceleration anywhere above 40mph. I’ll see if it gets any better with more break in time, as I’ve not driven it too far yet.
Seems like the luck of the draw…I just dropped off my 9" center section for a winter upgrade. Also doing 3.89 ratio but Richmond. Using the Powertrax Grip Pro which is a spiral gear posi “like” the Eaton Trutrac. Upgrading to Moser 31 spline axles too. A friend recommended this driveshaft company that I’m using so I just use the brands/combos they are comfortable with. My transmission is the 6R80 so my first gear (SLR) is crazy.