Couple of forward drum questions

[mikestertwo]

. The best source for billet drums is Scott Mclay. I have seen issues with others billet drums
The only billet part that is really mandatory is the drum IMO.

I totally agree. I also have seen issues with other billet drums from run out to shaft tolerances. The ones I get from Scott McClay Engineering are drop ins. Very high quality.

 

[Mike T]

I wonder if the run out truly makes the direct drum move up and down or if the clearance between the two allows for a little wiggle room? Has to be tons of them out there running like that.

 

[INEEDAGN]

The direct drum rides on the center support so it won't make the drum itself wiggle per say, it will, however, make the direct clutches shuffle up and down in relation to the steels with every revolution, which is a lot at the top of first gear. Forward drum spins 1:1 with engine rpm for 1 through three but the direct drum is hauling ass in 1st and in the opposite direction to boot. Harmonics of the situation might tax the direct drum and forward drum (center support) bushings more too. Not ideal by any means but like you said there's probably tons of them out there like that including maybe a couple I've built because I've never checked it. Add another item to the list

 

[Mike T]

The direct drum rides on the center support so it won't make the drum itself wiggle per say, it will, however, make the direct clutches shuffle up and down in relation to the steels with every revolution, which is a lot at the top of first gear. Harmonics of the situation might tax the direct drum bushings more too. Not ideal by any means but like you said there's probably tons of them out there like that including maybe a couple I've built because I've never checked it. Add another item to the list

That's the scenario I pictured. Bet they could be trued up in a press if done carefully.

 

[INEEDAGN]

I'm trying to envision the situation in third with the direct drum and forward locked together by the directs. If the clutches are offset a few thousandths it should still lock together and run "true" on the center support as a unit but it would be off balance by a little or maybe a lot depending on how much wobble it has. Then again the balancing of the direct drum is something I've pondered and never got any answers to when I asked publicly about how every drum has a different series of notches in the outer diameter

 

[INEEDAGN]

As far as shaft tolerances do you mean the pilot bushing for the input shaft tolerance and pocket depth? One builder who's drum I used flat warned me the pilot would be better with a used bushing because they reduced the inner dimension. And not all but most seem to need to shorten the input shaft pilot, some only barely which is actually more dangerous for a novice builder because you could physically get it to bolt together that way depending on end play settings. Always stab the input shaft in the drum and verify it bottoms. I had to chamfer the pilot bushing once because it was so shallow it hit the taper on the input shaft. That same drum was tight on the pilot bushing and I had to fine sand the bushing to get it to fit nice (not the drum the builder warned me about, he physically mailed me a used bushing for that one and it did fit fine)

 

[Mike T]

Also noticed the back end of the billet shaft had a much rougher finish than the stock unit, it started to grind into the selective thrust washer.

 

[Mike T]

Interesting link showing the original patents on the billet shafted forward. After opening the link click view pdf to see the drawings




http://www.google.com/patents/US20020182002

 

[mikestertwo]

As far as shaft tolerances do you mean the pilot bushing for the input shaft tolerance and pocket depth? )

No. I had one drum where the shaft would not fit into the center support. It was too big in diameter. I also had one where the shaft was too short. Even with the thickest selectable spacer it had way too much end play. I have had them with as much as .100" run out. I have not had any problems with the pilot bushing. Since I went to the drums from Scott McClay Engineering I have never had a problem.

 

[Mike T]

Since I went to the drums from Scott McClay Engineering I have never had a problem

Went to his site and the picture isn't that great, looks like the shaft is weld/spiced in the middle?

 

[mikestertwo]

Went to his site and the picture isn't that great, looks like the shaft is weld/spiced in the middle?
View attachment 313100

The shaft is not spliced. It's one piece. I have put these drums in transmissions that were dual fed and with transbrakes and never had a failure.

 

[TexasT]

careful trying to true it up with a press. Apparently some aren't welded with enough penetration.

 

[Mike T]

OH NO!! Did this happen to yours?

 

[TexasT]

not mine, just a pic I collected while researching for my build. I'm using a stock forward drum and not dual feeding. I have the shifts where id call em "crisp" and hopefully it will do. I doubt I'm putting 400hp into it with the stock turbo, down pipe and ic. I'm on a budget and a $400 billet shaft forward drum didn't make it onto the ledger and if it had I doubt swmbo would have approved it.

here is another for giggles

 

[Mike T]

swmbo

Never thought I'd see the day but I know what you mean

 

[TexasT]

if I thought I really needed one id have gotten approval, but I'm as big a tight wad as she is so I didn't even try.