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What internally makes the 4L30E Transmission a POS ?

1K views 2 replies 3 participants last post by  CalG 
#1 ·
What is it about the 4L30E Transmission that makes it so problematic?
Can it be beefed up with better overhaul or rebuild components?
 
#2 ·
Its just too small for the weight of the trucks. The transmission functions fine in other cars like the BMW's it was used in. Those cars even went on to use the 5L40E which was kind of an evolution of the 4L30E.

Bottom like is they should have used the 4L60E.

There are a few mods you can do to beef it up. Number on would be to install a big cooler.
 
#3 ·
Unattended fluid leaks is the catastrophic failure mechanism.
Faulty shift solenoids give the small issues.
Statistically, I doubt the 4L30e is any more problematic than a couple dozen other popular OEM transmissions across all product lines.

Check out the ZF 5HP24? Lot's of "commentary" on the net. I've had two rebuilt and running a third. Near 200K miles on all of them.

My own Trooper with the 4L30e blew the input seal with near total fluid loss. (117K miles) I "think" it was a low fluid issue, but how would I know, I never checked! ;-) DIY rebuild was less than $500 with a new TC. Except for the bell housing/adaptor that needed machining to accept a custom input bushing, everything inside was in good shape.
That was several years ago now, still going strong ;-)

Pulling heavy trailers is hard on any transmission.
 
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