Have an '08 Chevy Uplander as a work schlepper. It has the 4T65E transaxle in one of it's final applications. It is somewhat notorious for a condition called "slip and bump," whereby one of the mainline solenoids is slow to respond and on acceleration from a stop the trans slips for a second due to low pressure, then hooks up with a bump... the severity of which is relative to throttle application. Obviously, the long term effect of this is a tranny job. The cure, if the trans is otherwise in good shape, is to replace a particular solenoid before the trans is damaged. There are a couple of other problems that could cause this symptom, but the solenoid is one of the most common.
Needless to say, my old schlepper started this behavior. Yes, I have maintained the fluid and it has about 15K on a change to the correct Dex VI oil and a new Filtran pan filter. Intended to add a Magnefine at service time but it's a tight engine compartment and I was busy and lazy. Never got the round to it!
Changing the solenoid is a fairly onerous project, involving removing most of the suspension from the driver side, loosening the subframe and hanging the powertrain assembly down for access to the side cover, under which is the valve body and solenoids.
Further research showed that it wasn't always or often a solenoid failure, but iron particles partly jamming the solenoids. According to John Eleftherakis and Abe Khalil, who have done a series of ATF studies for the OE trans manufacturers and the aftermarket starting in the late '80s, approximately 90 percent of the contamination in a trans is metallic; 51 percent of that being ferrous (iron/steel), 21 percent copper, 11 percent aluminum and 7 percent lead. The particles range in size from 5 to 80 microns, about 82 percent of them larger than 5 microns. Obviously the exact mix is going to vary but it's clear that much of it is iron and that a pan filter at 80 um is going to let a LOT of it pass.
So, what is a solenoid? An electromagnet! Over time, it attracts ferrous particles. If enough attaches, it can begin to cause trouble.
The GM community has discussed this problem at length and because it's a very common inter/platform gearbox. There was a LOT to wade through. One of the consistent themes was to add more powerful neodymium magnets to the pan internally, both as a cure and as a prophelactic. Well, hey, I had a Magnefine ready to go! Might as well try the easy cure first.
As most of you know the Magnefine consists of a 30 um filter and a very large magnet, past which all the cooler line flow has to pass. Now, 30 um filration is not the most whizbang number by itself, but if you consider the magnet will catch 95% of the ALL the iron, regardless of size, (a number given to me years back by Magnefine and one I have little cause to doubt), and since iron is half the overall metallic contaminant, then it does pretty well indeed.
Found a place to install the Magnefine, cut and flared the cooler line, and installed it. This was about three months back. I noted the problem about three times the first time I drove it and it hasn't happened since. Three months and about 3K miles later, it hasn't happened again so I am provisionally declaring the problem cured. If it desn't happe for a year, I'll call "CURE!" out to the heavens and thank the transmission gods for bestowing a favor upon me.
Needless to say, my old schlepper started this behavior. Yes, I have maintained the fluid and it has about 15K on a change to the correct Dex VI oil and a new Filtran pan filter. Intended to add a Magnefine at service time but it's a tight engine compartment and I was busy and lazy. Never got the round to it!
Changing the solenoid is a fairly onerous project, involving removing most of the suspension from the driver side, loosening the subframe and hanging the powertrain assembly down for access to the side cover, under which is the valve body and solenoids.
Further research showed that it wasn't always or often a solenoid failure, but iron particles partly jamming the solenoids. According to John Eleftherakis and Abe Khalil, who have done a series of ATF studies for the OE trans manufacturers and the aftermarket starting in the late '80s, approximately 90 percent of the contamination in a trans is metallic; 51 percent of that being ferrous (iron/steel), 21 percent copper, 11 percent aluminum and 7 percent lead. The particles range in size from 5 to 80 microns, about 82 percent of them larger than 5 microns. Obviously the exact mix is going to vary but it's clear that much of it is iron and that a pan filter at 80 um is going to let a LOT of it pass.
So, what is a solenoid? An electromagnet! Over time, it attracts ferrous particles. If enough attaches, it can begin to cause trouble.
The GM community has discussed this problem at length and because it's a very common inter/platform gearbox. There was a LOT to wade through. One of the consistent themes was to add more powerful neodymium magnets to the pan internally, both as a cure and as a prophelactic. Well, hey, I had a Magnefine ready to go! Might as well try the easy cure first.
As most of you know the Magnefine consists of a 30 um filter and a very large magnet, past which all the cooler line flow has to pass. Now, 30 um filration is not the most whizbang number by itself, but if you consider the magnet will catch 95% of the ALL the iron, regardless of size, (a number given to me years back by Magnefine and one I have little cause to doubt), and since iron is half the overall metallic contaminant, then it does pretty well indeed.
Found a place to install the Magnefine, cut and flared the cooler line, and installed it. This was about three months back. I noted the problem about three times the first time I drove it and it hasn't happened since. Three months and about 3K miles later, it hasn't happened again so I am provisionally declaring the problem cured. If it desn't happe for a year, I'll call "CURE!" out to the heavens and thank the transmission gods for bestowing a favor upon me.