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Discussion Starter · #1 ·
I just found a core '88 3L80, maybe a 3L80HD I don't know yet, for sale at a very good price. Came out of a dually. It currently has the bolt-on rear yoke, but I know there is a conversion yoke available to make it a slip-yoke. I fully intend to rebuild this unit before using it, as the owner claims reverse is starting to slip.

Are there any issues I need to be aware of before going to pick this dude up? I plan on using it behind my 454 I'm collecting parts for. Since I'm buying it as a rebuildable core, $25 seems like a great price. Any opinions or advice???
 

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I'm running the same bolted tail shaft on my 540-- I'ts really no issue as long as you run the standard 400 slip yoke .. The apply pin in reverse servo needs to be pretty close to perfect.. Also I'm finding out more and more that low oil pressure and reverse chatter is being caused by a bad valve body leaking through! I can't tell you the nightmare I just went through with that one... By the way if this is supposedly an 88 it's the second year of the valve body gasket change.. Make sure you install the right one..
 

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Thanks for the heads-up Frank, greatly appreciated.:shakehands: I haven't been inside a TH400 since '85 and I'm a little rusty. So a standard slip-yoke from a TH 400 works with no issue? I thought that with the bolt-on type output shaft a special modified yoke was needed.
Talked to the owner this morning, said it would slip in reverse when backing a trailer, otherwise worked great for having 212,000 miles on it. Maybe a low/reverse servo seal leaking, or band adjustment? I'm going through it anyway, so it really doesn't matter at this point.
Just one more question; how can you identify the difference between a 3L80 and a 3L80HD? Internet searches tell me a 3L80 was used in light trucks, where the HD was used in heavy trucks, motor homes, buses, etc. Is a 1-ton dually considered a light truck? Seems like a dumb question, but...
 
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