My own 98 Blazer transmission oil and filter change went without a hitch. I thought I could do the same for a friend who also drives a 98.
I thought the job went smoothly.
No dice! Drive was slipping when we were done though all other gears worked fine.
He then took it to a transmission shop of his own choosing and they charged him 350.00 bucks to get it working again.
The call was...... we were supposed to remove the battery cable before doing this job.
So apparantly I am just a screw up now, though I am driving a perfectly functioning Blazer myself!

Can anyone verify this thing about the battery or did we just get hosed??

 

I have never disconnected the battery cables during a fluid/filter change. There really is no reason to do so.

Given that the transmission controls are adaptive, disconnecting the battery will serve to reset the controls to factory default, but the only case were not doing this would have an impact on performance would be if there were some problems with the transmission to begin with that might have been solved by the fluid/filter change. Typically, transmission problems are not 'solved' through a fluid/filter change as the only thing that can clog up a filter are parts of the transmission itself...

 

Are you referring to a 74 Blazer as your handle might suggest?

I agree that oil and filter changes will not cure tranny ailments. I did notice an improvement in shifting with my own vehicles however, following such maintenance via filter/oil changes(though I didn't disconnect any batteries).

The thing is that drive function was working fine before, and we were simply doing maintenance that was long over due on this 98 Blazer.
No doubt the tranny was not absolutely perfect beforehand(173,000 kms..... never maintained). The oil was dirty but not burned.

I know we used the right filter to correspond with the pan depth.
I just do not know why drive was slipping afterwords in this particular case and all other gears worked okay(no clunking). The pan is in a tight area and hard to manipulate. We pryed on the transfer case to move the mounts for extra millimeters.

Are you sure a 98 Blazer and newer needs no battery disconnect?
I don't see why either unless there is some silly sensor detecting no oil level that may then mysteriously effect/energize some other function.
We did run through the gears without starting(key partially on and no oil) to make sure I had the shifter bracket in the right pan holes.
Since when are vehicles so complex that you can no longer even do maintenance without being a rocket scientist? A 98 isn't what I would call new either.

Though the money is spent, I need to know if the transmission shop hosed my friend as it appears I need to prove it now to appease this friend. I do not want to look like a goof either!
I have Emailed another tranny shop with the question and am awaiting their response.
Anybody's input is greatly appreciated!

 

I have a '74, but considering that the transmission in that truck has absolutely no electrical connections to it... No, I am not referring to that vehicle. I have owned a number of vehicles and worked on too many others to count that were equiped with the 4L60E transmission that your truck has. I have done transmission fluid/filter changes on many of them and never disconnected the battery.

All I can say is that I have not disconnected the battery on any that I have ever changed and never had the problems you experienced.

 

Yeah ive also changed fluid/filter on my trans and never had issues like that. Sounds like the trans shop was definetly hosing ya. I change my fluid annually too so thats many changes with no issues. Ive heard that when trans fluid goes unserviced for too long that it can cause problems if u do decide to change it.

Or maybe something got shorted while removing pan/or filter. Did any wires get pinched or pulled on? It is a tight squeeze out with the pan

 

The '97, 205k mi., 2WD., automatic was doing fine. But still, some SuperTech Dexron/Mercon 3 surely couldn't hurt. And surely, somebody had to of changed the fluid at least once in 205 thousand miles? Unloosened the top automatic transmission feed line coming out of the side of the radiator, and flushed about 2 to 3 qts. at a time by starting & shutting off the engine. Automatic transmission fluid was brown/red. Original. 205,000 miles worth. Still, no burnt smell, no metal shavings. Replaced 95% of the fluid on that flush & figured I got most the rest when I replaced the filter a week later & had to drain & add 2 to 3 more quarts. Even though the fluid is now cherry red, the transmission shifts no different.

 

Thanks guys for your input. I had no problems with my own 98 Blazer either after the job, but it is my friends vehicle that is acting up(and the friend).
I thought we may have damaged the solenoid units that hang down into the pan area and make the pan removal difficult when cross members and exhaust pipes are in the equation. The wires on these units face foreward though, and I doubt we pinched them.
Any way, a response from Mr Transmission shed light on things.
They said something like: "So not disconnecting a battery during transmission service can cause damage?" "Ya, right!" "And low tire pressures can cause poor radio reception!"
Pre existing problems can become more apparant following a transmission oil change. Still. it is better to have that old oil abrasive oil out of there.