TH400 Who all is running one and??

[wb_7354]

I’m thinking of going with a TH400 with reverse manual valve body. Is there anything I need to know about swapping? Drive Shaft length? Will it use my stock Speedometer cable? What gear speedo gear? What torque converter? It will be going behind my 109 std. bore stroker. Approximately 650-750hp or maybe more. Is there anything else I need to consider?

Thanks, Bill


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[pacecarta]

driveshaft is about 3/4- 1inch shorter and needs a th400 trans yoke
speedometer cable screws right in , just need to have the correct gears in the th400 for your tire height and rear gears
youll need a converter
cooler lines are reverse of a 2004r as far as which is out and which is return but you can use the original steel 2004r lines with a little bending
trans mount can reuse the 2004r mount if you slot the holes for the slightly wider spacing on the th400
you can use the stock shifter with a th400 gate (try gbodyparts.com) or youll need an aftermarket shifter that will work with a three speed auto
youll need a BOP belhousing pattern th400 or an ultrabell
if it has a Tbrake youll need an sfi trans shield or a SFI trans blanket
who evers th400 trans you go with when it has a rmvb Tbrake its a constant pressure valvebody and its important to be sure the pump has the converter charge restrictor mod done or it will take out your thrust bearing

 

[wb_7354]

driveshaft is about 3/4- 1inch shorter and needs a th400 trans yoke
speedometer cable screws right in , just need to have the correct gears in the th400 for your tire height and rear gears
youll need a converter
cooler lines are reverse of a 2004r as far as which is out and which is return but you can use the original steel 2004r lines with a little bending
trans mount can reuse the 2004r mount if you slot the holes for the slightly wider spacing on the th400
you can use the stock shifter with a th400 gate (try gbodyparts.com) or youll need an aftermarket shifter that will work with a three speed auto
youll need a BOP belhousing pattern th400 or an ultrabell
if it has a Tbrake youll need an sfi trans shield or a SFI trans blanket
who evers th400 trans you go with when it has a rmvb Tbrake its a constant pressure valvebody and its important to be sure the pump has the converter charge restrictor mod done or it will take out your thrust bearing

Great info. Thanks. Could you please explain the converter charge restrictor mod? What thrust bearing? How is the mod done?


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[dank GN]

You have to reduce the size of the converter charge hole in the pump . If you don’t you will be runing a risk of wiping out your crank thrust bearing due to the converter pressing so hard against the flex plate . Just google th400 converter charge mod . If u need someone to do it u can shoot me a pm I actully still have all the stuff to do it .

 

[wb_7354]

Ok. I’ll look it up.


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[wb_7354]

You have to reduce the size of the converter charge hole in the pump . If you don’t you will be runing a risk of wiping out your crank thrust bearing due to the converter pressing so hard against the flex plate . Just google th400 converter charge mod . If u need someone to do it u can shoot me a pm I actully still have all the stuff to do it .

I’ll google it. You are a little bit far away for me to have you do it. Thanks for the offer.


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[wb_7354]

So I bought a used freshened th400 that was in a turbo Buick. It has trans brake and rmvb. I need to check to see if the pump mod was done.

What are the best shifter options?

I also need a dipstick. Will the 2004-r dipstick work?

Anything else I need to know to swap this into my GN?


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[pacecarta]

i like the B+M quicksilver , its a ratchet shifts are positive and no chance of pulling past your next gear
fits under console plate if you remove the front mount plate from the tunnel and trim a little plastic
i think the 2004r tube works but i like the lokar dipstick
most going to a th400 are fast enough to be required to have a locking dipstick
the lokar satisfies that rule but you could also use a locking dipstick from a truck and shorten the stick and notch it so it reads correctly for the th400 or remove the dipstick and just use the locking handle to seal the dip tube
doing a vent catch can isnt a bad idea either , you can tap the vent port for 1/8npt and use push-lok fitting

 

[wb_7354]

i like the B+M quicksilver , its a ratchet shifts are positive and no chance of pulling past your next gear
fits under console plate if you remove the front mount plate from the tunnel and trim a little plastic
i think the 2004r tube works but i like the lokar dipstick
most going to a th400 are fast enough to be required to have a locking dipstick
the lokar satisfies that rule but you could also use a locking dipstick from a truck and shorten the stick and notch it so it reads correctly for the th400 or remove the dipstick and just use the locking handle to seal the dip tube
doing a vent catch can isnt a bad idea either , you can tap the vent port for 1/8npt and use push-lok fitting

Great info. I’ll look at the Lokar dipsticks. Good idea also for the vent


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[DoubleD]

I have a metal locking dipstick on mine that works very well, a locking TH400 one from summit for a car should work fine. I was never very partial to the Lokar flexible ones. I also heard the plastic dipstick grows quite a bit with temperature, but haven't done any additional research on that claim.

I'm happy with my 400, it has a CK pro-tree brake in it now, which is fantastic. I use the factory shifter with the 3 speed plate in it. I have disconnected the linkages to the dash though (naughty naughty) but it allows for much lighter shifts this way.

Now would be a good time to upgrade from the factory driveshaft, rather than just having the factory one shortened with a new Yoke. I believe it to be money well spent.

Oh and having a great converter in the car will really help you both on the street and on the track, since you no longer have OD. I have the old converter from mine, but it is kinda crap. Its free though if you come get it.