4L60E Forward Sprag Broke Again
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TECH Junkie
Joined: May 2012
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From: Poplarville, MS
4L60E Forward Sprag Broke Again The forward sprag broke in my WS6 for the 2nd time in 6 months. After the 1st time I install the Sonnax HD 2-3 shift valve thinking I should not have this problem again. I am using the Borg Warner 29 element / dual cage sprag. Are there better parts that I should be using? Am I missing something, clutches and sprag assemblies are not cheap, please help.
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From: Ann Arbor, MI
I am not aware of better parts.
Are you racing in [D3] since you the Sonnax 2-3 shift valve?
Did you feel the difference with that shift valve? In [D3] you really fell the 3-2 downshift.
Did you check the entire sprag assembly for some deformation that is straining the sprag?
Are you racing in [D3] since you the Sonnax 2-3 shift valve?
Did you feel the difference with that shift valve? In [D3] you really fell the 3-2 downshift.
Did you check the entire sprag assembly for some deformation that is straining the sprag?
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TECH Junkie
Joined: May 2012
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From: Poplarville, MS
Really haven't been racing it. A few hard starts up through the gears, all in [D3]. The inner and outer races that I used were used pieces but I did not feel like any wear in them. I am going to use a rebuilt sprag assembly from PATC for around $60 and install a new Borg Warner 29 element sprag in it. These assemblies new go for $220to $350 and no telling what sprag is in them.
Teching In
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What are some things that cause a failed forward sprag? Having troubles my tranny was just rebuilt a week ago and it already broke. Not to mention it blew a tranny line off twice so I'm sure that didn't help it. But what are some more reasons.
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Joined: Aug 2010
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From: Ann Arbor, MI
Anyone interested in posting, should read Ryan33's thread where he documents that he lost 4-5 quarts of ATF while driving! Not sure how that would damage the sprag (heat or lack of lubrication?), but IMHO it is the primary factor.
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Broken sprag I keep having the same problem with mine any advise? No boom just a hard take off shifted in to second just fine then went into neutral going to third. I don’t have the sonnax 2-3 shift valve but when I tear it apart again I’m going to install it. This will be my third sprag in the past 4 months the last Borg Warner lasted 2 weeks. Thought it was the big tires so I put it on stocks but it still broke. Motor is around 450hp to the crank. And I have it on a stock tranny tune. All red clutches through out, 5 pin planetarys, beast sunshell, transgo hd2 shift kit. I don’t know what else to do other than an 80e swap cause I keep breaking that sprag.
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TECH Junkie
Joined: May 2012
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From: Poplarville, MS
Dana from Probuilt Automatics told me to do this. I feel the key is in having an inner race with no wear. Also it doesn't matter what you do if you have wheel hop, no sprag will hold to to that abuse.
The later 29 element sprag from Borg Warner (PN A74658D Transtar number) is 12.7% wider than the normal 29 element sprag from Borg Warner. I have used these for when the normal sprag has been problematic. It is a "dual cage" and one of the cages is nylon, and has bronze guides instead of the steel ones. It must be used with a 4L60E overrun hub. You should grind in 6 oil slots on the bronze guide that faces the overrun hub for better oiling like the steel guides have. Use the steel guide as a "template" for adding the oil slots. The inner race must have no wear and must be perfectly flat and have a "mirror" finish. The outer race should be flat and rough and use 36 grit and sand it in the direction of rotation by rolling it across a wooden bench and do it about 15 - 20 times. Rinse with solvent and blow it off with high pressure air, same for the inner race.
When useing the transgo hd2 shift kit I recommend not useing any of the washers in the 2nd accumulator, you can make this trans shift too and and it will beat itself to death
The later 29 element sprag from Borg Warner (PN A74658D Transtar number) is 12.7% wider than the normal 29 element sprag from Borg Warner. I have used these for when the normal sprag has been problematic. It is a "dual cage" and one of the cages is nylon, and has bronze guides instead of the steel ones. It must be used with a 4L60E overrun hub. You should grind in 6 oil slots on the bronze guide that faces the overrun hub for better oiling like the steel guides have. Use the steel guide as a "template" for adding the oil slots. The inner race must have no wear and must be perfectly flat and have a "mirror" finish. The outer race should be flat and rough and use 36 grit and sand it in the direction of rotation by rolling it across a wooden bench and do it about 15 - 20 times. Rinse with solvent and blow it off with high pressure air, same for the inner race.
When useing the transgo hd2 shift kit I recommend not useing any of the washers in the 2nd accumulator, you can make this trans shift too and and it will beat itself to death
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Joined: Jun 2008
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From: Nitro Alley
I keep having the same problem with mine any advise? No boom just a hard take off shifted in to second just fine then went into neutral going to third. I don’t have the sonnax 2-3 shift valve but when I tear it apart again I’m going to install it. This will be my third sprag in the past 4 months the last Borg Warner lasted 2 weeks. Thought it was the big tires so I put it on stocks but it still broke. Motor is around 450hp to the crank. And I have it on a stock tranny tune. All red clutches through out, 5 pin planetarys, beast sunshell, transgo hd2 shift kit. I don’t know what else to do other than an 80e swap cause I keep breaking that sprag.
If so... I would highly recommend changing to a 8.5" - 9.75" diameter torque-converter.
Lock-up can be retained if you wish in a 9.5" or 9.75" torque-converter.
The Sonnax 2-3 shift valve set will be of good help as well as:
-Make sure any and all bushings (in the front end especially) are in square and do not have any uneven ware.
-Install a new Borg Warner dual cage (one nylon/bronze and one steel) input sprag as suggested above by BBOND105 with his set-up recommendations from DANA @PBA.
-Double check all end-play
I usually see stock input-shaft failure before sprag failure, once set-up properly.
Good luck
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Joined: May 2006
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I have modified my idea of sanding the outer race as I had in the past. The early 4L60E sprag came with the outer race having deep machined grooves in them. At first, I thought that GM had made a mistake in not putting in the grooves in the outer race. So I added them for awhile. The later outer races from GM, had changed to a smooth outer race. Since then, GM has kept the outer race as smooth as the Inner race. This is similar to the TH400/4L80E direct drum setup. Having seen many TH400's have very little problem here. GM must have thought the same with this setup also. I started polishing the outer race (the same as the inner race) about 2-3 years ago. This is what I recommend to do here, on these. This is a summary of what I have learned on this in the last few years. The inner race must be perfect. And use the later extra wide sprag with the adding of additional lube holes in the retainer as mentioned above.
Last edited by PBA; Feb 24, 2020 at 03:16 AM.
TECH Junkie
Joined: Dec 2012
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From: Iowa
I still prep the outer race with emery cloth. 36 grit by hand for 30 seconds or so works great.
If we're being completely honest, I'm not sure it makes a huge difference either way. Run the tall sprag (plastic cage), run the sonnax HD2-3 shift valve, and try not to tire shake or 4-1 downshift the thing at 30mph WOT and it'll probably be fine in almost all cases
If we're being completely honest, I'm not sure it makes a huge difference either way. Run the tall sprag (plastic cage), run the sonnax HD2-3 shift valve, and try not to tire shake or 4-1 downshift the thing at 30mph WOT and it'll probably be fine in almost all cases