A little different beast - TH425

[fog]

I'm now in the process of rebuilding the trans, and have a question.

"To correct the leak created by dual feeding, the reverse feed side of the center support must be plugged. That can be done in the center support itself by tapping the hole and installing a set screw or it can be done with a cup plug in the case at the reverse feed into the center support."

Now, in TH425, there is a check-ball with a holder in that hole. Is this still the correct hole?

Also, where should the "added lubrication" hole be on this picture?
And witch one would be the converter feed to make smaller.

The needle bearings are 20 needle units, and new ones did not come with the kit, will those hold a season?

I really don't know what this trans will hold, but I'm aiming for 725 RWHP right now. I'm not plugging the accumulators to have a little softer shifts to save the chains life a little.

 

[fog]

And furthermore, what mods to do and what to avoid to get it to hold the needed power, but have a little less positive shifts to spare the chain.

Would this build sheet do:
direct dual fed.
trans-go kit.
reduce converter feed mod.
increase lube feed mod.
accumulator mod _not_ to do.

 

[jakeshoe]

OK,
You aren't showing the center support and I would have to see a tech manual to confirm the reverse feed but it SHOULD still be the drivers side feed hole beside the center support bolt.

I would not do the full time converter lube mod.

I would dual feed it, install a heavy duty intermediate sprag, heavy intermediate snap ring, I would leave all the checkballs in place. Leaving out the 1-2 checkball is giving it a .187" feed which is WAY too much. .125" is maximum, I would probably go .110" on this application, .125" for the 3rd feed, and leave the 2-3 accumulator alone if it is like the TH400.

I would need to see both halves of the pump to tell you what to restrict for the converter feed.

 

[fog]

Thanks,

The trans is bolted to the table so, that everything goes in from the up, as with TH400.

I would not do the full time converter lube mod. -- Check.

I would dual feed it -- Check

install a heavy duty intermediate sprag -- 34 element, Check.

heavy intermediate snap ring -- int. power pack. 4 clutches and HD ring. Check.

I would leave all the checkballs in place -- Check.

Leaving out the 1-2 checkball is giving it a .187" feed which is WAY too much. .125" is maximum, I would probably go .110" on this application, .125" for the 3rd feed, and leave the 2-3 accumulator alone if it is like the TH400.
-- This I have to trace, witch ones should those be.

I would need to see both halves of the pump to tell you what to restrict for the converter feed. -- I'll look into it.

 

[fog]

..
.125" is maximum, I would probably go .110" on this application, .125" for the 3rd feed, and leave the 2-3 accumulator alone if it is like the TH400.

I would need to see both halves of the pump to tell you what to restrict for the converter feed.

I think the TransGo kit shows the nessecary holes:
.85 i assume is for 1-2 and .110 is for 3rd so those I'll up to .110(bit form transgo kit) and .118(3mm bit that I have)

Pump halves. I color coded the matching holes also:

 

[jakeshoe]

The checkballed hole should be reverse. Check the circuit by air checking it. Reverse will leak out the third side stock ,but 3rd will seal up and not leak out the reverse side.

 

[fog]

The checkballed hole should be reverse. Check the circuit by air checking it. Reverse will leak out the third side stock ,but 3rd will seal up and not leak out the reverse side.

Okay, so if I have left out the lip seal and cast iron ring for the dual feed, should I still plug the hole?

Thanks in advance.

 

[jakeshoe]

If you can trace the circuit back from the hole with checkball and be sure it goes to the reverse circuit at the manual valve.
Do you have an ATSG manual for it?

 

[fog]

If you can trace the circuit back from the hole with checkball and be sure it goes to the reverse circuit at the manual valve.
Do you have an ATSG manual for it?

I'll try. I don't have a manual for 425 but have for a 400. but I have done part cross-referencing and the center support is same part number for 400 and 425.
There is no manual available in online transmission part shops, I have looked trough most of them.

 

[fog]

I traced the circuit in the valve body and yes, it ends up being the reverse.

Now the open questions still remain. Do I plug it, the converter feed, 20 needle bearings and the drill sizes.

The valve body itself will probably travel back to states to Kevin for the stage right. I have myself looked trough the schematics a lot, but no good idea, how to implement reverse feed during 1st.

 

[jakeshoe]

Yes,
it will have to be plugged if you dual fed it.

Hole sizes are already answered. No good way to plug the converter feed that I can see, just measure the cooler line pressure, I doubt you will have issue with it.

Jake

 

[fog]

Thanks a million.

Now I can take it apart again for drilling, tapping and cleaning.

 

[jakeshoe]

If you can extract the checkball capsule assy, just drive a 3/8"cup plug in place there. You could even drive the shank of a 3/8" bolt cut to make a plug in there.

No reason to do a bunch of drilling and tapping if you can avoid it.

 

[fog]

Okay, the trans is almost together, 3/8 was a tad small, i could get the ball seat out and tapped the hole with M10 skank.

Now, on to a transbrake.

I have worked trough a ton of hydraulic circuits and...

There is a check-ball before rear servo that closes the 1st feed in reverse and vice-versa. Now, if this check-ball seat could be modified so, that it only blocks the 1st feed in reverse but not reverse feed in 1st the reverse circuit would be filled also in manual 1st.

Now, the manual valve will exhaust this feed, but the groove that does that has no effect in any other range.

So, if I make a new manual piston that does not have this groove and modify the check-ball seat so it will bleed one-way, it should give me a transbrake

Disclaimer: I'm not a transmission specialist by any means, this is the first automatic that I have taken apart. Do not follow my footsteps

 

[KL Mallender]

Hi Fog, got your message, don't worry about sending VB to me, I'm sure I can find a core around here, somebody will have a few of those beasts lurking, just that it will take a little while for weather and time to break, get your unit working properly as is to make sure we don't get crossed up if a problem should arise(not that screwing around with cars would ever get us in trouble, LOL ) the good news is that I made the "Stage Right" for the 400 as well as others, the real problem with 350/400's is that it is real easy for the pump to get stupid with over-pressurising as these transmissions did not have a "blow-off" failsafe as the 200/700's do, which can wreck havoc with blowing out intermediate snap-ring lugs in the 400, let alone center support sealing ring problems. I have a big interest in your project, anything this nutty in the power-to-weight department has got to produce more than a few giggles, just hope she doesn't get too light in the front down track
Good Luck brother,

Kevin.

 

[jakeshoe]

If you guys need a valve body I can probably source one.

 

[fog]

Thanks guys!

I have one contact also in states now who has some 425-s lying around. Just got steeper diff and some other axle parts from him some days ago.

Kevin, don't worry about the crossing. I'm 100% sure it will be my rebuild that will kill this trans the first time
I cant verify my build before, since the car will be ready 2011 the quickest. If I finish the trans, I have to start working on the blown SII engine that needs a rebuild also with a sleeve. All takes time and cash

But I can fill the timeslots with working on a friend's GN

 

[Hacksaw]

If you replace the waved steels in the Intermediate & Direct Clutches with flat steels, it will firm up the 1-2 & 2-3 shifts. But, that might hammer the chain too much. The Forward & Direct steels interchange, but are different thicknesses. That way you can adjust clutch clearances. I've been quoted .030" to .050" for both of those on the 400.

Just make sure you ALWAYS start with the steel plate against the clutch pistons in all 3 of the clutches when building! Very bad things will happen if you don't!!

The Direct Clutch feed hole on the older TransGo 400-2 Racing kits was .165", so you have some room there to go up, again depending on the chain. I think .110" & .118" are good starting points.

Because of the obvious wear in the pump area, I would have the pump cover & case area machined flat.

If you're using a GN power plant, install the vacuum modulator spring, if it has it in the TransGo kit. This will keep your shifting points from going too high.

Also, use some kind of vaccuum-boost bypass kit for the vacuum modulator! Like TransGo's VBP-VAC. Boost into the vacuum modulator will send the line pressure in the transmission sky high if you don't!!

 

[fog]

If you replace the waved steels in the Intermediate & Direct Clutches with flat steels, it will firm up the 1-2 & 2-3 shifts. But, that might hammer the chain too much. The Forward & Direct steels interchange, but are different thicknesses. That way you can adjust clutch clearances. I've been quoted .030" to .050" for both of those on the 400. Just make sure you ALWAYS start with the steel plate against the clutch pistons in all 3 of the clutches when building! Very bad things will happen if you don't!!

Hmm, I have to look into it. I think the Kolenes that I got are all same thickness. I need to tear it down one more time anyway. there are 40-roller bearings in the mail.
I think I should change the waved steels. I am retaining the accumulators, so retaining both may slow the clutch clamping too much.
The Forward one had been replaced before by not-so-brilliant tech. It had 5 steels, waved and 4 frictions. Obviously those were burned to ashes.

If you're using a GN power plant, install the vacuum modulator spring, if it has it in the TransGo kit. This will keep your shifting points from going too high.
Also, use some kind of vaccuum-boost bypass kit for the vacuum modulator! Like TransGo's VBP-VAC. Boost into the vacuum modulator will send the line pressure in the transmission sky high if you don't!!

Yes, I learned this the hard way last season with 3800T+4T60E.

 

[fog]

...I'm sure I can find a core around here, somebody will have a few of those beasts lurking, just that it will take a little while for weather and time to break...

So, how's the weather The snow has almost melted here.

Not that I have time to work on that trans. All time goes to having the only GN here to the track in 4 weeks...

But I found a next-best-thing after spool to the trans I think Looks like GM 14-bolt 9.5" powertrax fits the TH425 carrier...