Change tranny fluid every 5000 miles and get better TCC Lock

Tooky

Tooky

Serious about performance
Guys I don't know if this is just my truck and how often I race it or what, but if I let my fluid go to 10,000 miles, the TCC lock doesn't even cause a downward RPM spike on Datamaster anymore and doing a quarter mile pass with TCC Lockup switch, my 3rd gear will start only in the low 3000s.

When I change my fluid I notice a dramatic difference that is felt by SOTP as well as shown and seen easily in Datamaster RPM graphs. When I changed it last Tuesday night, my RPMs during a pass with TCC Lockup switch going from 2nd into 3rd gear went from a weak 3400-3500 to 2925!! 500 RPMs of extra grab in the tranny by draining 5000 mile old fluid.

I also didn't find the Mobil1 fluid worth anything over standard generic Dexron III. It seems like it had to be changed just as often. From now on I will run the generic Dexron III I get for free from the tap at the shop where I have access to a lift.

So if you're someone who is changing your fluid every 15,000 or 30,000 or whatever GM recommends or you've never changed it, I would say to do it as soon as you can and see what kind of difference you feel! It can't hurt. If I just floor it normally, when my TCC Locks at 69mph in 3rd gear, it feels like a 20HP boost of power!!! You can really feel it. Also if you watch the tach, you can watch the needle go up and then DOWN when the TCC locks! This is a stock original tranny and converter. Yours could (and should!) work like I just described!! If not, the prime suspect would be the ATF in my opinion. Just trying to share some insight I have learned, with others.
 
JSM

JSM

Active member
I found in my truck, type F fluid was the best in both shifting and heat.

At first I thought I was imagining things, but last time changes to dextron and temp went up 20+ deg.

Be curious if someone else could duplicate that.


This is what I have heard about type F vs Dextron, although I have not confirmed it.

GM uses a higher pump pressure with dextron type fluid
Ford uses lower pump pressure and makes up for it with a fluid with friction additive, hence type F.

Anybody know more than I do about this subject, if my theory is correct, etc.?
 
Hu Ryde

Hu Ryde

Donating Member
Several people like the type F fluid and it works. Only bad thing about it that I have read is that if it is heated up too much it will break down more easily than say Synthetic because of its intended use. Use a large cooler and you should be golden with Type F.
 
Tooky

Tooky

Serious about performance
I received some questions on my post about the TCC fluid so I will illustrate further. First off when I drained the fluid I will admit my tranny had experienced a failure causing metal fragments BUT I also have noticed the same results in prior fluid changes even when the tranny was 100%. Anyways, the point I'm saying is that the fluid was only 5000 miles old and it smelled perfect and looked bright cherry red, and it was some of the best synthetic ATF money can buy, yet when I changed it I had a dramatic improvement in my TCC Lock. If your fluid is so bad you can tell by color or smell, its WAYYYYY beyond time to change it (if you're trying for 100% all the time like I am. I guess if you just don't care or don't drag race much then this may not concern you.)

Anyways allow me to illustrate.

Look at this first Datamaster sample. Comments below.
dm_tcc1.png

These tests do not use TCC Lockup switch but illustrate the same thing. You can see I finish 2nd gear (the first sharp point in red RPM line) and then 3rd gear starts and when TCC Lock applies at 69 mph, it only drops from 3875 RPM to a paltry 3825! So basically it just "holds" the 3800 range for a second.

Now two days later just by changing fluid & filter, look at these results:
dm_tcc2.png

The difference in 3rd is easily seen. TCC applies and it takes the RPMs from 3725 to 3450! You can see the dip on the red RPM graph very easily and even watching the tachometer in the cab you can see the needle move downwards mid-gear. When this happens it feels like a power boost forwards. So if your WOT Datamasters look like my first picture, then I'd recommend start investigating the solution by changing fluid & filter.

FWIW when I did quarter mile passes with TCC Lockup switch (like when I drag race), the run on the first image only dropped the start of 3rd gear to 3450. On the second image when I changed the ATF, 3rd gear with TCC Lock started at 2925!! Quite a difference.

Finally be careful if you don't have a drain plug tranny pan yet, cause you're in for a real mess if you've never changed it before. When you start to drop the bolts it will look like this!!! (This pic is from my Turbo Grand Prix but trust me it's just as bad on our trucks)
tranny_drain.jpg
 
Syclone#2960

Syclone#2960

What ever it takes!!
JS Manufacturing said:
I found in my truck, type F fluid was the best in both shifting and heat.

At first I thought I was imagining things, but last time changes to dextron and temp went up 20+ deg.

Be curious if someone else could duplicate that.


This is what I have heard about type F vs Dextron, although I have not confirmed it.

GM uses a higher pump pressure with dextron type fluid
Ford uses lower pump pressure and makes up for it with a fluid with friction additive, hence type F.

Anybody know more than I do about this subject, if my theory is correct, etc.?
Click to expand...

Does your truck have a stock tranny?
________
Weed Vaporizer
 
Last edited:
C

cr133r

New member
Only slightly related, but I found the best drainpan a DIYer can use for doing tranny fluid changes: Go to your nearest Walmart and buy one of their huge storage containers (I got a big grey Sterilite brand one), as big as you can get. They cost 6-10 bucks and are quite a bit larger than the tranny pan as well as having high enough side walls so that the splashback doesn't come up and over the sides.
 
K

kwick6

Donating Member
cr133r said:
Only slightly related, but I found the best drainpan a DIYer can use for doing tranny fluid changes: Go to your nearest Walmart and buy one of their huge storage containers (I got a big grey Sterilite brand one), as big as you can get. They cost 6-10 bucks and are quite a bit larger than the tranny pan as well as having high enough side walls so that the splashback doesn't come up and over the sides.
Click to expand...

or buy one with a drainplug. ;)
 
C

cr133r

New member
kwick6 said:
or buy one with a drainplug. ;)
Click to expand...
Very true, but you have to pull it apart a first time. I forgot to put the drain plug in the pan this last time I put the tranny in, so I guess I have one more time to make a mess.
 
9

93ty475

Donating Member
tooky emailed a while back about asking me about something i did to my truck...very sharp guy...he did a great job in dialing in his truck....
 
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