Type 911 Intermediate Plate Bearings A Little Loose

[Scott Clarke]

After the acceptance of the inevitability of replacing the pinion and input shaft intermediate plate bearings (pitted races) I went about what I thought would be the difficult task of removing the old bearings. However, after removing the retaining plate, a few taps with a punch was all it took. The factory workshop manual goes on about heating the plate and using a press to remove. Clearly the bearings were not as tight in there as they once were. My new bearings will arrive this week. Should I use some sort of loctite-type bearing mount product when installing them? Should I be concerned about how loose they are?
-Scott

[Nine9six]

If the bearing race is to loose, just do as I did and wrap one layer of cellophane around the outer bearing race. Cellophane is very uniform in its thickness. (.001"). As the bearing heats up the cellophane will melt and act as a type of loctite on the outer race.
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Yeah, of course I'm kidding...Yes you should be concerned about how loose they are. But it kinda sound like I knew some special trick about fitting bearings to worn bearing housings, didn't it?

[ChrisBennet]

Don't toy with us so Nine9six!
-Chris

[Grady Clay]

Aah, you know these NorCal guys, the fog comes in under the bridge and clouds their … Well you get the idea, HeHe.


Scott, please post some images of the “pitting.”


First take a high quality micrometer and bore gauge and measure both new and old bearing ODs and the intermediate plate bore ID. Pay particular attention to the roundness of the bore and any taper. Calculate the interference or clearance. To get accurate measurements, you will have to have everything stabilized at room temperature. If you don’t have the tools, go to a precision machine shop.

I have a bottle of Loctite product called “Sleeve Retainer” that I have successfully used. The problem is it isn’t listed on their consumer products site and their main industrial site is down. I’ll try again tomorrow.

Over the years I had been back into several of the same transmissions for syncros, re-gearing, etc. and found it to have worked as intended. I went to great lengths to have everything perfectly clean and prepped. On assembly I used differential heating/cooling. On the bearing OD you need to apply the product prior to cooling and keep its axis vertical. I was always afraid of getting some product in a bearing but with care that never was a problem.

Best,
Grady

[Scott Clarke]

Thanks, Grady. I'll make some measurements when the bearings arrive. I'll get to the photos also.
-Scott

[Joe Bob]

I just went thru this with a 915 trans. I had Randy Aase of Aasco machine a sleeve and press it into the milled intermediate shaft area and then press in the race.

WEVO also has a fix. His was more of a turnaround time than what I could wait for and Randy had an opening...but I did use a WEVO bearing retainer as extra insurance on a repeat problem.

www.wevo.com

[Scott Clarke]

Grady-
Here are the "X" races. True to form, the input shaft race has the big potholes in the surface. Someone was driving around without enough oil in the gearbox. It wasn't me! The pinion race, as you can see, has a matt finish area where the ball bearings run. Let me know if other images would be helpful.

Mike-
How loose were your bearings?

[ischmitz]

There are four or five different fixes:


0. Do nothing. Yours was still tight. That's O.K. Use the solid Wevo bearing retainer to add some more strength to the box.
1. There is a glue that is used to seat bearing races. Cheap but questionable in my book. It seems under temperature its strength won't hold up to real abuse.
2. We have "fixed" MikeZ's box by machining out the race seat and putting in an 2mm aluminum ring. Everything was a press fit and all work was done at an expert machine shop for less than 300$. On top of that we used the Wevo solid retaining plate. This should hold up O.K. to the 3.6 torque for a while
3. Get a new case ($$$$$) or a good used one (risky)
4. Wevo machines out a figure eight and puts in a steel figure 8. This is the best money can buy but it also comes with a cost of more than 900$ for the work.

It all depends on how much power you plan to run through the box and what reliability you would like to get out of it.

[Scott Clarke]

I finally got around to measuring the bearings and bore. I must admit that my measuring shills are questionable, but I think that I can confidently make some general statements.

The new and old pinion bearings are, as far as I can tell, the same size. This dimension is .0001" larger that the bore in the intermediate plate. There does not seem to be appreciable taper or out of roundness in the bore.

The new input shaft bearing is .0005" bigger than the old one. The bore in the intermediate plate, however, averages about .0007" larger than the bearing. I can not press the bearing into the plate by hand. I'm going to check Loctite's website concerning sleeve retainer. I'd appreciate some input on how much of an issue these clearances represent.

Does Wevo make the bearing retainer for 901/911 gearboxes, or just for 915s?

Thanks in advance,
-Scott

EDIT- Loctite Sleeve Retainer 640 seems to be widely available.

[Joe Bob]

Ask Hayden direct....
www.wevo.com