4L60 pump bushing too small?
Thread Starter
TECH Apprentice
Joined: Jan 2023
Posts: 340
Likes: 47
From: Corpus Christi, TX
4L60 pump bushing too small? Replaced all the bushings in this build 320k it definitely needed them. Pump bushing is definitely too small and wont begin to go over the smooth part of the input housing shafts smooth surface it rides on. I have done close to 5 of these recently and many more years ago and this is the first time running into this. It is an entire alto kit which I have never tried from summit SUM-705066. I assumed only the clutches were going to be alto the gaskets and seals came in some packaging other than Transtec not sure the brand. This kit also came with offbrand black pistons unlike the usual National.
I guess I am just wondering if this is common? I plan to try and measure how much smaller it is than the shaft tomorrow before i beat it out and replace it.
I guess I am just wondering if this is common? I plan to try and measure how much smaller it is than the shaft tomorrow before i beat it out and replace it.
TECH Junkie
Joined: Dec 2012
Posts: 3,614
Likes: 1,326
From: Iowa
Are you referring to the stator bushing?
Front or rear?
Only real way to know is to get the snap gauges out and measure with a micrometer
Sometimes bushings are too tight after press fit shrinks them...but 9/10 times a bushing doesn't fit it's improper install rather than a junk bushing
Front or rear?
Only real way to know is to get the snap gauges out and measure with a micrometer
Sometimes bushings are too tight after press fit shrinks them...but 9/10 times a bushing doesn't fit it's improper install rather than a junk bushing
TECH Junkie
Joined: Dec 2012
Posts: 3,614
Likes: 1,326
From: Iowa
If you are referring to the front stator bushing and you drove it in until it bottomed on the shoulder...it's squished. Drive it out, get a new bushing, and try again.
Leave it slightly above the shoulder.
And use an arbor press rather than a mallet
Leave it slightly above the shoulder.
And use an arbor press rather than a mallet
TECH Resident
Joined: May 2006
Posts: 969
Likes: 119
The aftermarket stator support, has an undersize bushing in the front. Instead of a .060" wall. This bushing has a .058" wall. This allows .004" extra clearance, which is way too much, and will cause problems. I remove this bushing and replace with the TH350C (extra wide) that has the correct wall thickness of .060". Plus it is bronze (copper colored) and not some kind of other material other than bronze (looks like brass) that these stator supports come with. This brings the clearance within spec. I change the bushing in the rear of the stator support, as they come with a narrow bushing (.430") for the extra wide Sonnax bushing (.510"). I have not been able to locate the oem extra wide bushing (.510") for this. Which I think is a better bushing than the Sonnax version.
Last edited by PBA; Apr 19, 2024 at 01:22 PM.
