C2/3 Posi Case 4 series??

[jim34671]

Can anyone tell me if the EDB 32298 case is a series 3 or 4?
The cutout windows seem larger than the '175' units that I'm used to but suspect this may be a later series 4???
Thx
Jim

[Craig S.]

Re: C2/3 Posi Case 4 series??

Jim - I have a 175 and a 298 here on my shop bench.....and as you say the windows are diffeent size on the opposite side from the posi installation window. They are both definitely 4 series cases....... I have a 3 series right next to them and the offset is different for the ring gear....Craig

[jim34671]

Re: C2/3 Posi Case 4 series??

Craig,
Thx.
Good to know.
I believe you and I discussed 4 series cases a couple of years ago.
First I've seen of these '298's..the larger cutouts sure to make life easier.
Jim

[Duke W.]

Re: C2/3 Posi Case 4 series??

"Three" and "four" series case mounting planes for the ring gear are offset different distances from the drive pinion axis due to different drive pinion pitch diameters. I think a "four series gear" can be used on a "three series" case if a suitable spacer is used, but I might have this backwards. As a general rule as ratio increases the pinion tooth count and pitch diamter decrease so the ring gear has to move closer to the drive pinion..

Which ever one has the greatest ring gear mounting plane offset from the drive pinion axis can be used with the "other" gear series with a spacer, but not the other way around.

Duke

[Craig S.]

Re: C2/3 Posi Case 4 series??

Yes - I think that was the prime reason for the change...a LOT easier to work throuth that window! Craig

[Craig S.]

Re: C2/3 Posi Case 4 series??

Duke - you are correct, the 3 series case has the flange a greater distance from the pinion and hence can accomodate the 4 series ring gear with a spacer. If I recall, the ring gear itself is thinner on the 4 series gears, and the pinion is much smaller in diameter. What Jim was noting though, was the vintage differences in the forging numbers on the cases, the older ones had a smaller window on the case on the side opposite the large window the posi clutches are inserted. This 4 series case has the last 3 digits ending in 175. I have one on my workbench now from a 66 carrier made in Sept 65 just like this. I also have a 4 series case with the last 3 digits ending in 298 right next to it, and this "backside window" is much larger, and hence easier to work on the posi when you install the cross gears etc. The 3 series cases may also have differing numbered cases, but I honestly don't know from personal experience. All I have worked on so far have the same forging case number with the last 3 digits ending in 117. Interestingly, these also have a "300" number opposite the case forging number, which I assumed also meant the series of the case. This is not true of any of the 4 series cases with the numbers I mention above. I am pretty certain the 298 case in 4 series is a newer version, changed by Eaton to make the assembly easier. Possibly this weakens the case, but there is still a lot of meat there. I do know these sometimes crack near the large window however, and should be inspected. Craig

[jim34671]

Re: C2/3 Posi Case 4 series??

Craig,
Despite the ease of building '298's'..I like the '175's' as they seem to look and feel more robust,having less material removed in the cutout areas.
Either way,is fine by me.
Thx
Jim

[Craig S.]

Re: C2/3 Posi Case 4 series??

I agree.....my preference would be the 175.......Craig

[Wayne M.]

Believe big-window 3-series is ED_32297_PM1

One was for sale on eBay a few months back.

Anyone care to take a stab at when Eaton changed to big-window design ? My GM 1970 parts book still shows the EDB_30175 and EDB_30117 for 4 and 3 series posi cases, respectively