4L65E Forward Sprag Questions
Thread Starter
Joined: Nov 2008
Posts: 2,423
Likes: 225
From: A-Town, Ill side
4L65E Forward Sprag Questions So long story short, I lost 3-4, and rebuilt my unit. It was my 1st rebuild. I bought parts from a vendor on here, and that was great. I got it back together, and within a week, the forward sprag went out. I couldn't blame anyone but myself for not replacing it when I rebuilt it.
I tore it back out, and all apart. Took EVERYTHING apart, and cleaned it in the parts washer. I changed the sun gear assembly with one from my parts transmission, but stuck a new sprag inside of it (BW steel cage). Everything looked good, and back together it went.
It has been together for about 3 weeks now. I rolled into the throttle pretty hard yesterday, and heard a noise. It reminded me of a belt squeeling. I believe I had heard this the last time, just before the sprag let loose. I am wondering, is there anything I may be missing, that could cause a forward sprag issue?
Thanks in advance!
I tore it back out, and all apart. Took EVERYTHING apart, and cleaned it in the parts washer. I changed the sun gear assembly with one from my parts transmission, but stuck a new sprag inside of it (BW steel cage). Everything looked good, and back together it went.
It has been together for about 3 weeks now. I rolled into the throttle pretty hard yesterday, and heard a noise. It reminded me of a belt squeeling. I believe I had heard this the last time, just before the sprag let loose. I am wondering, is there anything I may be missing, that could cause a forward sprag issue?
Thanks in advance!
TECH Resident
Joined: May 2006
Posts: 969
Likes: 119
When replacing the overrun sprag, you must inspect the inner race closely. It must be "flat" and very smooth. If flat, polish it with 600, 1000, and finally with 1500 sandpaper in direction of rotation. If it is not flat, it "must" be replaced. With the outer race it should be flat also, and roughen it up with 36 - 50 grit in direction of rotation. Rinse both thoroughly with mineral spirits. There are two late sprags from Borg Warner. The standard steel retainer 29 element with a dual cage and the later bronze retainer 29 element with a dual cage, one of these cages is nylon. This later sprag has 12.7% wider sprag elements than the standard sprag. You must use the 4L60E overrun hub when using this later bronze retainer sprag in the 700R4 transmission, otherwise rapid wear of the 700R4 bronze retainer that contacts the overrun hub will result.
Last edited by PBA; Aug 29, 2017 at 06:04 AM.
Thread Starter
Joined: Nov 2008
Posts: 2,423
Likes: 225
From: A-Town, Ill side
Thanks Dana. I have spoke with you about this when it happened. So far, it seems good. I will be calling soon again though, I have another question about my valvebody, that doesn't seem to make sense to me.
TECH Junkie
Joined: May 2012
Posts: 3,050
Likes: 716
From: Poplarville, MS
When replacing the overrun sprag, you must inspect the inner race closely. It must be "flat" and very smooth. If flat, polish it with 600, 1000, and finally with 1500 sandpaper in direction of rotation. If it is not flat, it "must" be replaced. With the outer race it should be flat also, and roughen it up with 36 - 50 grit in direction of rotation. Rinse both thoroughly with mineral spirits. There are two late sprags from Borg Warner. The standard steel retainer 29 element with a dual cage and the later bronze retainer 29 element with a dual cage, one of these cages is nylon. This later sprag has 12.7% wider sprag elements than the standard sprag. You must use the 4L60E overrun hub when using this later bronze retainer sprag in the 700R4 transmission, otherwise rapid wear of the 700R4 bronze retainer that contacts the overrun hub will result.
