TH400 filter change

[DokWatson]

I decided to change the filter to see if it change the harsh shifting my TH400 had. It was never bad enough to bother me, but it was a noticeable 'clunk' between gears. I read somewhere this can be caused by a dirty filter. A new filter from napa comes with an o-ring, pan gasket, and filter for less than 15$. Long story short, it did fix the problem. Shifts a lot smoother now, might be something to try for those of you trouble shooting your transmission.

 

[beetleswamp]

Glad to hear it's happy. I put a drain plug in when I did mine.

 

[OLDCHEV4X4]

Glad to hear it's happy. I put a drain plug in when I did mine.

Yes , that can be a real messy job with no drain plug and no lift. Nothing like laying on your back with trans fluid running everywhere.

 

[Barrman]

A filter changed help mine with the smoother shifts as well.

I have a 1/3 mile dirt road to go down for access to my house. Before the filter change, the truck would stay in second gear as idled down the dirt road at about 10 mph. There is a slight hill to go up and down on this road. After the filter change, it would down shift to 1st just before the peak of the hill. Very smooth downshift that I couldn't feel, just hear.

I didn't even think about the drain plug until I was putting the pan back on. However, when we serviced the Air Force c20 Suburban for Warthog. We put a plug on it. He should enjoy his fluid changes more now.

 

[JUNKYARDJOHN]

I like to put a remote oil filter inline on my trucks tran.s line. It sure makes changing the filter a snap, doesn't cost much & has to filter the tran.s fluid about 100 times better than that glorified screen. Also I tend not to put it off till next weekend. Im basically a lazy sh t. John

 

[original]

Don't forget to add the lucas transmission fix. I run it in everything. It will make the smoothest shift smoother.

 

[Matt65]

Mine sometimes shifts so hard when making a turn from a stop it will bark the tires shifting into 2nd. This surprised me with the 37s, it must be a pretty strong shock load for the drivetrain. Its smooth once warm, and always smooth into 3rd.

I may have to look into the filter or additive. Some say firm is good, but to what degree?

 

[zout]

Hey DW - Sea Foam makes a great product to put in with your fluid to help clean the valve and system - also a good pre fluid change flush thought here !!
FWIW

 

[motormayhem]

Mine sometimes shifts so hard when making a turn from a stop it will bark the tires shifting into 2nd. This surprised me with the 37s, it must be a pretty strong shock load for the drivetrain. Its smooth once warm, and always smooth into 3rd.

I may have to look into the filter or additive. Some say firm is good, but to what degree?

I think tire barking may also be from the locker engaging. Mine shifts hard, but not that hard, just a solid bam into the next gear.

 

[ODdave]

Guys, be carefull how much Additives & mods you do to try to make your THM400 shift smoother. The 400 has a firm shift and is designed that way, a shift you dont feel is a slipping shift. Fluids now days have become far superior to those of the past. It is NOT nesesary for additives in a properly working trans and many of them contain a "seal swelling" agent (kerosene) and it breaks down rubber.

 

[DokWatson]

Mine sometimes shifts so hard when making a turn from a stop it will bark the tires shifting into 2nd. This surprised me with the 37s, it must be a pretty strong shock load for the drivetrain. Its smooth once warm, and always smooth into 3rd.

I may have to look into the filter or additive. Some say firm is good, but to what degree?

The detroit locker exacerbates the issue since its designed to have a little play in the rear drive shaft. Before the filter change, if I gave the truck some heavy throttle it would **** near bounce my head off the rear glass when it shifted.