Replacement Torque Converter: driveability & longevity vs stall speed

[Killer223]

can someone explain the 900/400 and 800/300 what do those number correlate to?
900 torque? 300 rpm drop from stock? bus isn't that all relative to the engine power?

 

[cerberusiam]

Those numbers have to do with the size and shape of the stator blades, it is a designation Dave uses to denote the design. The flash and full brake stall will change with power levels, that's why nobody tries to rate a TC as a 200 or 300 drop flash stall because it is dependent on input TQ. If they do rate them it is based on stock power.

 

[AEdelheit]

Dave has some good technical write ups on his website, anyone wanting to know more about TCs should spend a little time and read through them.

 

[Regcabguy]

I had an 89% DTT TC and the trans would get real hot in line heading north at the San Ysidro border where waits could be 1+ hrs. I would constantly have to shift into neutral to keep the temps down. Driving, the temps were very low. The new recommendation sounds more like it for the average owner.

 

[PawsWet]

Update: got a call the next day from Dave's partner, Bob. He spent a good deal of time with me, addressing each topic on my list. The plan we came up with for my application is:

- Triple disk billet 17SS (stock stall) TC
- Sonnax billet one-piece input shaft
- 4140 steel 2nd gear band apply lever, strap, and anchor
- Goerend valve body

After thinking about it, I'm adding the master rebuild kit and having a full rebuild done while the transmission is out. This is well above what I planned to spend, but I will enjoy the piece of mind. I'll put the VB in myself, as phase II, on my next set of days off.

If I understood correctly (big if), the locked 3-OD shift concern can be resolved by controlling (usually +) the unlock circuit pressure. They do not expect issues with my stock VB, but I'll report what I find before and after I put in the Goerend VB upgrade.

 

[BigPapa]

That's basically what I did with mine and it's great.

I don't understand what you're saying about installing the VB. Why not replace it while the transmission's out getting rebuilt?

 

[promisedland]

You are getting your paws wet, With trans fluid
Good deal! Please keep us updated!

 

[Bob4x4]

No mention of flex plate?

 

[AEdelheit]

I would do the VB while the trans is being built, dont see any advantage to waiting.

 

[promisedland]

No mention of flex plate?

^^ agree
I put a Georend flex plate in my trans when I did my build.

 

[PawsWet]

The VB will take longer to ship than the rest of the parts, which are in stock and in transit now. I was hoping to get it out of the shop before the VB was ready.

For the flex plate, I planned to take a chance by waiting to see what the condition of the stock flex plate was before deciding which way to go. I won't be having the stiffener welded onto the factory flex plate in any case. That seems like an invitation for stress cracks in the heat affected zone of the welds.

Anyone have a factory flex plate fail during normal driving or towing? I see where this is going..my wallet is about to get even thinner.

 

[AEdelheit]

I have seen a few break, the cost of a flex plate now will be much cheaper then just the R&R to replace it later! Yes it turns into a huge snowball effect and cost more then planned but the piece of mind knowing its all done right is worth the $$$, well at least thats what I tell my self.............

 

[cerberusiam]

I have over 280k on a stock flex plate with upwards of 400 HP and 900 TQ run thru it most of its life. Lots of heavy towing and some playing. From what I have seen the broken flex plate is from pre-existing damage from a non-billet TC or just abusive use. Every single failure I have seem has the mounting holes wallowed out causing them to be loose and a twist to start in the plate. If the mounting bolts are loctited in to a billet cover TC and tightened correctly little issues in normal to heavy use are seen. Check your flex plate whne it is out to see if there is any damaging starting. PATC has a 4 mil plate for a reasonable price that should suffice unless an SFI rated plate is needed. Depends on what you want to spend and when.

 

[BigPapa]

Good call on the flex plate. I ALWAYS forget something.

Cerb is right, you may not need one, and he is correct on the bolts, but, I went with the stiffener plate myself. Had it TIG welded and haven't had any issues. The way I see it, you may not need the billet input either, but you're going with it so it doesn't need to be revisited later, correct? Same deal with the flex plate.

Is the truck in the shop now? Do you need it back before the VB will be available? I'd wait and do it all at once if at all possible.

Just my $0.02....

 

[Bob4x4]

A billet input shaft should not be considered optional when you use a tripple disc............

 

[PawsWet]

The billet input shaft is in the shipment with the first batch of parts. As far as the flex plate, I will wait to see how the stock one looks. One thing I can't stop thinking about is whether the added stiffness of a machined forged steel piece, vs a stamped steel plate is a good thing. A flex plate has that name for a reason. It's supposed to flex some with engine-transmission vibrations. A rifle barrel vibrates like a tuning fork when fired, and the "tune" affects accuracy. The crankshaft and input shaft centerlines may be statically aligned, but offset slightly during peaks of vibrations. If the flex plate is where that motion is designed to be absorbed, then is stiffening it a good thing? Yes, I'm probably over thinking this.

While it would be easier to put the VB in with the rest of the parts, the lead time for that assembly is longer, since it is hand made, tested, and tuned by Goerend. I am very motivated to get my truck back (daily driver), but I'd prefer they take the normal amount of time on the VB. They said it will take x days +/-, and I'm good with that. We separated the shipments so I could let the shop finish everything else and get my wheels back. Other than cleaning up the incredible mess I'm likely to make, doing the VB myself seems straightforward. It may take me 10x as long as a pro, but on my days off, that's ok. I'll feel good about it when it's done. Maybe my updates will be entertaining for those of you who have been there/done that.

 

[BigPapa]

Yes, I'm probably over thinking this.

Absolutely.

.

 

[Bob4x4]

The billet input shaft is in the shipment with the first batch of parts. As far as the flex plate, I will wait to see how the stock one looks. One thing I can't stop thinking about is whether the added stiffness of a machined forged steel piece, vs a stamped steel plate is a good thing. A flex plate has that name for a reason. It's supposed to flex some with engine-transmission vibrations. A rifle barrel vibrates like a tuning fork when fired, and the "tune" affects accuracy. The crankshaft and input shaft centerlines may be statically aligned, but offset slightly during peaks of vibrations. If the flex plate is where that motion is designed to be absorbed, then is stiffening it a good thing? Yes, I'm probably over thinking this.

While it would be easier to put the VB in with the rest of the parts, the lead time for that assembly is longer, since it is hand made, tested, and tuned by Goerend. I am very motivated to get my truck back (daily driver), but I'd prefer they take the normal amount of time on the VB. They said it will take x days +/-, and I'm good with that. We separated the shipments so I could let the shop finish everything else and get my wheels back. Other than cleaning up the incredible mess I'm likely to make, doing the VB myself seems straightforward. It may take me 10x as long as a pro, but on my days off, that's ok. I'll feel good about it when it's done. Maybe my updates will be entertaining for those of you who have been there/done that.

Stock torque convertor=45lbs Tripple disc=90lbs................

 

[Killer223]

No way would I suggest messing with the VB, its effects to much, and one mistake and you'll hate the trans or it'll eat it's self.*

 

[PawsWet]

Won't be modifying the valve body. I'm just swapping it out for a better one.