Re: 904 vs 727 sprag
[Re: cudaman1969]
#2076676
05/19/16 07:21 PM
05/19/16 07:21 PM
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Joined: Sep 2004
Posts: 2,091
oberlin, Ohio
Rapid340
top fuel
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top fuel
Joined: Sep 2004
Posts: 2,091
oberlin, Ohio
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The stock 727 sprag is not fastened to the case very securely. The 904s are fastened with some heavy duty rivets from the factory. You can find aftermarket bolt-in 904 sprags but the 727 bolt-in are more common.
1971 Factory Appearing Duster 340 11.000 @ 122 mph
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Re: 904 vs 727 sprag
[Re: cudaman1969]
#2076701
05/19/16 07:46 PM
05/19/16 07:46 PM
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Joined: Jan 2003
Posts: 74,962
U.S.S.A.
JohnRR
I Win
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I Win
Joined: Jan 2003
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U.S.S.A.
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Why is the 904 considered safer the the 727 as far as exploding the sprag? Lighter weight parts? Sprag is close to same size but drums are quite a difference. I want to put the 904 stuff in a 727 case and want to get input on whitch low drum to use (a little work on each to make work) . Rest is easy so far. Thanks Lightweight parts mainly. The mass of the 727 drum coupled with how it's made is the problem , the 904 drum is a lot smaller. also the 904 sprag is pinned to the case, but it can still fail, it's just doesn't have the explosion risk of the front drum near as much ... I had to say that instead of it doesn't  ... you can put 904 parts in a 727 , it's already being done but it's pricey as I think there are some specialized parts . The clutches and bands are smaller though so you'll have that issue to deal with. Probably cheaper to put a 'glide in it ?
running up my post count some more .
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Re: 904 vs 727 sprag
[Re: Rapid340]
#2076755
05/19/16 08:56 PM
05/19/16 08:56 PM
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Joined: Jan 2004
Posts: 8,233
fredericksburg,va
cudaman1969
OP
master
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OP
master
Joined: Jan 2004
Posts: 8,233
fredericksburg,va
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The stock 727 sprag is not fastened to the case very securely. The 904s are fastened with some heavy duty rivets from the factory. You can find aftermarket bolt-in 904 sprags but the 727 bolt-in are more common.
I was going to drill out the rivets and install bolts but that would work better, I'll pm you. There is a lip that holds the sprag that I need to machine off, it hits the back of drum, no big deal. Also have to make new anchor for band now, all doable.
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Re: 904 vs 727 sprag
[Re: JohnRR]
#2076762
05/19/16 09:08 PM
05/19/16 09:08 PM
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Joined: Jan 2004
Posts: 8,233
fredericksburg,va
cudaman1969
OP
master
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OP
master
Joined: Jan 2004
Posts: 8,233
fredericksburg,va
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Why is the 904 considered safer the the 727 as far as exploding the sprag? Lighter weight parts? Sprag is close to same size but drums are quite a difference. I want to put the 904 stuff in a 727 case and want to get input on whitch low drum to use (a little work on each to make work) . Rest is easy so far. Thanks Lightweight parts mainly. The mass of the 727 drum coupled with how it's made is the problem , the 904 drum is a lot smaller. also the 904 sprag is pinned to the case, but it can still fail, it's just doesn't have the explosion risk of the front drum near as much ... I had to say that instead of it doesn't ... you can put 904 parts in a 727 , it's already being done but it's pricey as I think there are some specialized parts . The clutches and bands are smaller though so you'll have that issue to deal with. Probably cheaper to put a 'glide in it ? I'm building a 69 cuda with a 383 to run in NHRA stock class, 904 guts should free up some hp and still pass tech. Most of the basic measurements are right on between the two trans but certain parts will have to be adapted.
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Re: 904 vs 727 sprag
[Re: cudaman1969]
#2077009
05/20/16 10:21 AM
05/20/16 10:21 AM
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Joined: Jan 2003
Posts: 74,962
U.S.S.A.
JohnRR
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I Win
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Call ProTrans, they do it all the time. I'm not that rich You say that and you are building a car to run in NHRA STOCK ??? I looked at the protrans sight and the 727/904 starts at 1695 plus the valve body , that is a lot cheaper than I was expecting , it would probably be enough to handle the 383
running up my post count some more .
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Re: 904 vs 727 sprag
[Re: JohnRR]
#2077364
05/20/16 10:29 PM
05/20/16 10:29 PM
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Joined: Jan 2004
Posts: 8,233
fredericksburg,va
cudaman1969
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Joined: Jan 2004
Posts: 8,233
fredericksburg,va
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Call ProTrans, they do it all the time. I'm not that rich You say that and you are building a car to run in NHRA STOCK ??? I looked at the protrans sight and the 727/904 starts at 1695 plus the valve body , that is a lot cheaper than I was expecting , it would probably be enough to handle the 383 I like doing it myself and have the only one but some have to buy everything then hope they got the latest greatest parts, you don't have to brake the bank to run fast or run under the index. I have zero cost in car so far other than labor and I'm not chasing a record.
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Re: 904 vs 727 sprag
[Re: dvw]
#2077368
05/20/16 10:33 PM
05/20/16 10:33 PM
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Joined: Jan 2004
Posts: 8,233
fredericksburg,va
cudaman1969
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fredericksburg,va
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The biggest hurdle is the combo at the front pump/reaction shaft support/input shaft. To gain any benefit you need to run the 904 drums and shells. It also requires a a new band anchor location due to the small drum diameter
Doug Going through that now, I'll be doing some welding and machining this week to see how the cleances work out.
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