th400 mods

[74huggerorange]

I am getting ready to swap to th400 in my truck (74 chevy k10) and the tranny I will be using is stock...I plan to fully rebuild it and do whatever mods would be best for a trail truck/rock crawler. I didn't know what the main weak points were or what mods were best. The transmission came out of a 84 m1008 with 6.2 diesel and will be behind a 350 running about 300hp.

The only thing I have on the list so far is full performance rebuild kit (tci most likely), performance front pump (tci again), and reverse manual valve body with engine braking (yep...tci again). What are some other things that I should do while I'm at it? Which convertor should I use? (obviously low stall is best) I am running a big transcooler and temp gauge and the tranny already has the deeper pan stock so I will most likely just plate the bottom and add a drain plug.

Thanks

 

[74huggerorange]

how much of a difference does the engine braking make?

 

[destinbeachman]

It makes a huge difference on the trail!

 

[74huggerorange]

ok, so definately get valve body...any other opinions?

 

[Ned Kelly]

Another good upgrade (I'd said mandantory just because it is double strength over factory and only costs $65 or so) is the 34 element sprague clutch. Summit racing has the TCI one listed as TCI-227900. I think the factory one is only 17 element.

 

[74huggerorange]

well, since mine is the mid 80's th400 it doesnt have the correct drum for the 34 element sprag so I would have to swap out the drum with an older one...does this still pertain to my transmission?

 

[Ned Kelly]

If I recall correctly it doesn't matter which drum you have (I may be wrong though, it's been awhile). The sprague will now have 34 dog clutches instead of 17. It's like a wheel bearing. Instead of having 17 roller bearings, it now has 34. The 34 element is not bigger or wider than a 17 unit one. Maybe check with a local trans shop to verify or let us know if I'm wrong.

EDIT: I do recall getting the larger drum installed on my TH400. Can't recall if it was only for more clutch packs though?

 

[Dunleavy2004]

I had to get a new drum when i rebuilt my T-400 with the 34 element sprag.

 

[sm1nts2escape]

You might as well spend 35 bucks and get a new reverse servo spring kit.Transgo sells it.It is called a harsh reverse fix kit.If you are going to tear it apart you might as well do this one easy cheap thing.I am rebuilding mine this summer/winter I bought a deep pan,harsh reverse kit,Transgo stage 1&2 kit, red alto w/kolene steels powerpacks,transtec overhaul kit,full bushing kit,hd allison filter and adjustable modulator kit off ebay.I am told the alto clutches grab the same but they are way more resileint to heat.The powerpacks add a couple clutches also.Biggest things you should want is a nice clean torque converter and trans cooler.Are you rebuilding this yourself?If you are do you know what you are doing?Chiltons rebuild book sucks it basically only shows diassasembly and reassembly pics.There is alot more involved than what chiltons shows.I highly reccomend the atsg service manual and how to work with and modify the turbo 400 book.Those two books have almost everything in them.My truck will hopefully only be a two year project.

 

[74huggerorange]

I will surely do that harse reverse fix and look into the 34 element sprag. I am planning to buy the tci reverse manual valve body with engine braking and use some ratchet shifter. I haven't decided on the rebuild kit just yet (transtec on ebay u say?) and I guess I need to look into the power packs also? I will use a new stock or towing convertor and I am debating whether to reuse the stock pump or buy a performance tci unit. I plan to either clean my transcooler or buy a new one as well.

As far as rebuilding it goes, I rebuilt a th350 8 yrs ago and thats about it...I have rebuilt engines, transfer cases, and axles though and am very mechanically minded so with a manual I think I will be fine. I really want to do this myself for the satisfaction and to learn more about how it works. I can take my time as this truck is not my dd.

 

[sm1nts2escape]

With 300 hp the only things you should need is a complete rebuild kit if the trans needs it a trans cooler and a good torque conveter.Shift kits do make the trans last longer because they slip less and can help when getting through the mud and rocks.