A833 aluminum main case - how durable?

[cody coyote]

Hi, Cody here - I recently ran across an aluminum overdrive transmission with the B/E body 2 position tail shaft housing. I was planning on getting the tailshaft housing to complete another transmission project I have in the works and it crossed my mind that I had never heard of anyone seeking out the aluminum main case for weight reduction issues - are they inherently weaker? Also, in the Passon book, the overdrive main shafts seem several inches shorter than the 30 spline non OD B/E main shaft - how is this so? I think the main cases and B/E body tailshaft housing are all the same length, correct?

 

[59pwrwgn]

The counter shaft is shorter on the 833od. It's not a press fit and therefore requires a plug to keep the lube in. The case isn't bushed for the counter shaft either. Sheel shaft in an oversized aluminum hole.

 

[gkent]

Significantly inferior to an iron case. As mentioned the countershaft is "floating" - not a press fit. As a result the front bore got significantly enlarged over time which led to gear mesh issues. I had planned to use one once and had a steel sleeve installed in the front. The machinist said the center of the existing hole was damn near 1/8" off !!

And another thing, I think some of the cases (maybe all) don't have a provision for a reverse detent.

 

[Daves69]

Also, in the Passon book, the overdrive main shafts seem several inches shorter than the 30 spline non OD B/E main shaft - how is this so?

For A-body, shorter trans I suspect.

This may be of interest to you...............

https://www.hotrod.com/how-to/transmission-drivetrain/mopp-0110-a-833-aluminum-case-buildup/

 

[gkent]

To add to my post, I had the case machined and bushing installed then built the box with 18-spline internals. The first issue was the front bearing retainer. Although both use the 308 bearing, the bolt pattern is different between the two retainers. Next issue was the missing reverse detent hole. So that had to be machined (you can't just drill and tap this !!). Next, the reverse lever seals differently than an iron case so you need the proper seal for that. From there assembly is pretty straight forward. Then I got chatting with the folks at Brewers - who are my go-to folks for 4-speed parts and info. Those guys advised not using the case regardless of all the mods. They pointed out that the weight savings of a mere ten pounds was not worth the risks. So I went home and swapped everything back into the iron case and that was that.

 

[Jeff Peterson]

 

[cody coyote]

Whoa - thanks to all for the information - was not expecting so much feedback so quickly.....the Brewer's pic and info is convincing - thank you Jeff, , GKent, everyone. More in a bit, here....nice knowledge base to tap into

 

[#41]

It depends on what you are going to do with it. The Brewers example... 500 inch Hemi in a heavy car power shifting into 3rd? I'm not surprised. It was not engineered for that. The aluminum case OD's were only intended for use behind mid-70's to 80's slant sixes and small block non-high performance engines.

You can machine in a bushing for the counter shaft to improve durability somewhat. I know several people who run them behind big block street cars. They make for a very economical overdrive as long as you respect the limitations. FWIW, I am running an unmodified aluminum case 833OD behind a 383 (500hp?). I race/cruize at 130-150mph and it will take the car to 165mph+.... I DO NOT hard shift due to the known weakness at the counter shaft. So far, no problems.