700R4/4L60/4L60E Front Pump Service

 Fundamentally, all automatic transmissions use the front pump simply as a hydraulic pump. it’s like a farm tractor uses a pump to run implements by supplying oil to the control valves- then to components to create a function. on a tranny we use the outer shell of the torque converter to drive the pump- then send the oil to control valves that dictate what comp0nents need to be fired off to create function.

On these transmissions,as well as the 4L80E, this is where they really set themselves apart from the older generations of trannys like the th350 and th400.S3700012 the older trannys used a gear type pump sandwiched between two  iron halves. they are known for wearing the gears into the pump halves creating internal leakage and loss of pressure. the end play is also adjustable via the washer at the back side of the pump around the stator hub. here in the picture is a newer style hydraulic pump made of aluminum. the thrust washer on these is not the adjustment however- the adjustment for end play is on the front of the input drum. they also switched to a vane style hydraulic pump over a gear type pump.  it also contains two of the control valve assemblies: the pressure regulator assembly and the torque converter clutch valve assembly.

there are several vanedifferent pumps and combinations throughout the years, so here again unlike the older trannys, the pumps cannot necessarily  be swapped around and are year specific to an extent. early 700R4 pumps ad a different size stator and smaller input shaft….and are considered undesirable. in the mid 80’s they beefed up the input shaft. early 700R4’s up to around 1987 also used a 7 blade vane pump. they are known for failure and also had an outer slide that was a fail point. later models beefed this up to a 10 vane pump and a hardened outer slide ring. later years of the 4L60E used a 13 vane pump. now, this was primarily done to smooth out oil flow for a more consistent output: better driveability. they all put out the same amount of oil flow. a 7 blade pump is considered obsolete if you ask me and if it were me , i would replace it with a 10 vane pump and ring set up. a 13 vane set up is kind of like 10 lbs of shit in a 5 lb bag. under high hp applications it can crack. so to me, if you have a 7 blade pump, i would upgrade to a 10 blade. if i have a 13 vane pump: if it is in good shape i would re-use it. a 10 vane i would simply check it for wear. at the very least if you want to re-use a 7 vane pump buy a new outer slide ring. also when switching around pumps, remember there are different witdth’s of pumps and cover halves- so be year specific. the wrong pump in the wrong half and you will be in deep shit!

there are a few seals for the gears in these pumps and are supplied in an overhaul seal kit. vanes can be replaced individually for wear. the front pumps of these are also known for the front seal comming out. early model 700’s are known for this and GM came up with a retaining ring that fits over the seal. if you don’t have one of these  on the tranny you’re working on they can be had cheap(scrap yard core pile) and are not a bad idea.  i have heard of guys drilling the drainback hole out larger in the pump cover to prevent the seal blowing out…..not for me i guess. also it is worth noting that newer style 4L60E pumps have a different converter support bushing in the front and some builders feel they are better. if necessary to replace a bushing, if it needs to be staked in place do it. the bushing will walk out of the front of the pump and take out the seal.

aside from inspection of the pump, the other areas you need to deal with in the stator shaft pump_valves_lineupcover/rear cover are the two valve passages. both the pressure regulator valve and the TCC valves are steel….in aluminum bores…..yeah it is a high wear area and MUST be checked. pictured here is the regulator valve and TCC valve locations, along with a referrence to modifications described later in this article.

 if there is a lot of slop around either valve……when you get hot weather and that fluid gets hot…..all sorts of goofy shit will start to happen. on the regulator valve it will basically lose optimum system pressure and cause all sorts of long term damage from slipping bands and clutches…..especially after you get a trailer full of scrap behind the truck on a nice july day. same thing with the TCC valve- good hot oil and you have oil leakage- the Torque converter will lock and unlock- slip. it will feel like you are riding on a bull if it gets extreme enough.both of these problems as odd as it may seem- may go away in the fall and winter. thicker oil and it won’t leak- or a can of lucas oil.

to be honest, checking the wear on these valves is a pain in the ass. i remove them- clean the housing real good and stick the valves back in the bores dry. if they seem real sloppy they need repair. Sonnax makes repair kits for both of these valves. you basically ream out the passage and install an oversize valve. the tooling is expensive as hell, it is usually cheaper just to buy a brand new pump or at least a new stator half than it is to repair the passages. so make sure you don’t have to repair these valve passages BEFORE you order pump parts for the vane pump. it will be cheaper to buy the whole damn thing. also on the regulator valve, there is a land you must either grind off or buy aftermarket. it is a service bulletin from the mid 90’s from what i can gather and is in the ATSG manual. it’s pretty simple. it is to improve lubrication and reduce pump fluttery noise that can occur.also i found referrence to also modifying a land on the TCC valve and changing the spring….also listed in the picture above, but they ARE NOT described in the ATSG manual, so all i can say is if you chose to do what is in the picture it is at your own risk, consult your tech manual and/or valve body kit you may be using.

the pressure regulator also contains the reverse boost valve and the throttle valve boost valve, or TV boost valve.boost the TV boost valve was also a problem area of these older trannys, and there are several different sizes available. as a rule of thumb, i always install a .500″ diameter boost valve. in the picture it is the one on the left and is the first one to come out of the regulator passage after removing the retaining clip. the larger diameter boost valve allows the throttle valve to ramp up pressure quicker for a better clutch apply. some builders prefer a .471 diameter over the .500″ diameter for driveability reasons. i prefer the .500″ simply because i rather have a stout shift than a burned up tranny in 6 months.

now i know iS3700041 have missed a few things here, cause there is a check ball, orfices, and what not, but i hope it gave you some idea of the major things to address on one of these new style pumps. also don’t forget to replace this straining screen. it keeps the shit out of the the TCC circuit i think. if it plugs it will do all sorts of goofy shit too……but if it is plugged the it is probably from stuff elsewhere that failed anyways. don’t forget to replace it. you get one of these in the overhaul kit too.

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