6.2l/Th400 any trans upgrades needed?

[5akman]

My son just bought an '85 C20 with the diesel and Th400. We're swapping the original engine of unknown history with an airport tug pull out engine that has a Banks turbo on it with performance pump and ARP head studs. While we're doing the engine install, he wants to pull the trans to do a hot pressure wash on it as its covered in 1/4" of sludge. While the trans is out, he's going to do a filter change but we're wondering if there are any upgrades that would be beneficial at this time such as shift kit, modulator change etc.

So, for those of you with a th400 in a 6.2l powered rig, would you do anything different to the trans if you had it out on the bench? His master plan is to add a Gear Vendors unit and, possibly swap out the 4.10 rear for 3.55 or 3.73 as this will be an around town daily driver and not a towing rig.

 

[Matt69olds]

Can’t go wrong with a deep pan (assuming it isn’t already equipped with one) and a TransGo shift kit. Get as much of the old fluid out, install the kit, run it until it needs a complete overhaul. Then there are many upgrades that could be made

 

[Blue Ox]

The turbo 6.2 isn't going to overpower a 400. Mild shift kit wouldn't be a crime but don't get silly with a daily driver. With the turbo you may do okay to move to a 3.73 rear, but I wouldn't go higher than that. With a natural I'd stick with the 4.10s.

 

[ABINIDI]

I have the 6.2 with a Banks, with a T400, and a GV overdrive. As stated, the 6.2 wont break the 400, but recently i went through my 400 and did the Transgo reprogram kit. Also There are also a ton of videos on Youtube to do Valve body mods for almost free for the 400, full manual, etc, which will improve the shifting/life of the 400. The one thing the TG kit gives you that helps a ton is the new spring for the higher pump pressure, which the 400 always does better with a higher pump pressure.

Deep pan = optional. I changed my pan for a standard one that has the drain plug, so its less mess when opening it up. Deep will give you more fluid = less heat, just make sure you get the longer filter pick up tube

Maybe replace things like the filter, valve modulator on the passenger side, check/inspect the governor gear on it ( known to go bad/strip sometimes)

If you take the valve body off and it has the big plastic front 2-3 servo piston, order a metal/aluminum one ( super cheap ) because the plastic ones can crack/break; known issue on the 400s... search Youtube... , or you can bypass it completely for firmer 2-3, which is what i did. ( remove spring and plug feed hole )

Replace both front and rear seals on it....You'll thank yourself later.

Get a trans temp gauge for it, just so you can know where its at. I have my sensor in the pressure port on the drivers side, works well.

These are easy things to do that add lots of improvement to the 400, without having completely tearing it down.