'04 SRT-4 engine in an '88 Caravan build

[Vigo]

Well, it's probably not from spinning street tires!

[wheming]

Is there a method to use a transbrake in that trans? Can that be done electronically?
Not a tranny guy, and it kinda sucks our trans' are usually a weak point (and always so at certain power levels)

[A.J.]

Dang. That really sucks.
That damage is from brake boosting?

I think it's a combination from brake boosting and welding.

Well, it's probably not from spinning street tires!

I have just enough turbo lag so I never spin my street tires. I do occasionally chirp the tires going into second.

Is there a method to use a transbrake in that trans? Can that be done electronically?
Not a tranny guy, and it kinda sucks our trans' are usually a weak point (and always so at certain power levels)

Don't know. I'm not going to worry about a trans brake when i have a 2 step launch control built into my PCM.

[wheming]

The 2 step built into the t-smec cal seems to work pretty well. I haven't played much with different settings, but had it set softer when first testing & tuning. Last time out had raised it to about 3200 to try for better 60' time. But this is an A413 with PTC converter.

[A.J.]

The 2 step built into the t-smec cal seems to work pretty well. I haven't played much with different settings, but had it set softer when first testing & tuning. Last time out had raised it to about 3200 to try for better 60' time. But this is an A413 with PTC converter.

My 31TH is the same as your A413. The main difference is the my starter is on the front and yours is on the rear. The 31TH came with some upgraded internals but everything is interchangeable.

[wheming]

My 31TH is the same as your A413. The main difference is the my starter is on the front and yours is on the rear. The 31TH came with some upgraded internals but everything is interchangeable.

It's solenoid shift though, right? All electronic? Would a lsd help reduce these stress cracks? Peloquins makes one for the 31TH although they haven't advertised it. I was going to buy one for my PT GT to have when needed. I think they only have a couple left.
You said that was the case that is cracking? The 3 speed cases are any stronger? There was a company making race autos for the PT and SRT4s, they were 3 speeds. I know you lose overdrive, but if you gain longevity...
And i don't find Mini bad to drive even around town.

[Vigo]

No, the 31th is just another name for an a413. In the mid 90s Chrysler changed their transmission naming system and everything changed names, like a604>41TE, a413>31TH, a518>42RE, etc.

Right at the same time, the 413/31th changed the case to use the newer 2.0/2.4 bellhousing. So if someone uses the term 31TH there's a very good chance they're talking about a trans for a 2.0/2.4.

As for the transbrake, it's no magic bullet. The 5spd guys break axles with shockloading due to all the 'tolerance stack-up' between the engine and the tires which lets all that rotating weight get a running start and then slam to a stop all at once, just like an impact wrench. The reason autos dont break axles as much is that whenever you are 'brake torquing/brake boosting' you have loaded up everything in between the engine and the tires and taken all the slack out of the system so that that can't happen. The downside of the trans brake is that it basically puts your ring/pinion/sidegears/cvjoints back into a 'loose' state which could lead to just breaking the axles, and it doesn't actually reduce the spreading load your ring/pinion gearset will see when the transbrake finally releases. So unless someone has an argument that addresses that, i think the transbrake doesn't really get you around the fact that you STILL have to reduce the spreading load at the ring/pinion interface to avoid the case breakage.

I think the long-term pie in the sky solution would be to be able to use the 4spd auto. You can gear it to have massively more gear reduction across the ring/pinion gearset than the 3spd does, which means you wouldn't have to put nearly as much input torque to it to get the same acceleration of the van in 1st gear. Plus, there have been a few of them with a lot of power put through them and i havent heard of one breaking like this yet.

[wheming]

Thanks for that insight and explanation! :beer:

[A.J.]

It's solenoid shift though, right? All electronic? Would a lsd help reduce these stress cracks? Peloquins makes one for the 31TH although they haven't advertised it. I was going to buy one for my PT GT to have when needed. I think they only have a couple left.
You said that was the case that is cracking? The 3 speed cases are any stronger? There was a company making race autos for the PT and SRT4s, they were 3 speeds. I know you lose overdrive, but if you gain longevity...
And i don't find Mini bad to drive even around town.

The 31TH is hydraulic like the A413. The electronic or solenoid shift transmission is the 4 speed and is the A604/41TE. The "T" is for transverse mounted, the "H" is for hydraulic and the "E" is for electronic.

I have a Peloquin and have been using one since I put the 2.4 in my van. It's awesome and I highly recommend one. BUT the preload on the differential bearings needs to be set correctly. I bought a $400 0-30 in/lb dial torque wrench just for setting preload properly. Also the Peolquin for the 3 speed is different than the 4 speed but both are available.

Darrel Cox Racing (DCR) builds 3 speeds for the 2.4 for racing and I have yet to see one hold together and be reliable. Nothing but complaints on SRT-4 forums about their automatic transmissions. On top of it being an unreliable transmission it's $8000 to boot. I can build my own unreliable transmission for FAR LESS than that. (New case $75, new pinion shaft $25, gaskets, seals, & thrust washers under $100).

No, the 31th is just another name for an a413. In the mid 90s Chrysler changed their transmission naming system and everything changed names, like a604>41TE, a413>31TH, a518>42RE, etc.

Right at the same time, the 413/31th changed the case to use the newer 2.0/2.4 bellhousing. So if someone uses the term 31TH there's a very good chance they're talking about a trans for a 2.0/2.4.

Since the 2.0/2.4 came out in '94 and the 2.5 went away in '95, I'm going to refer to the starter-in-front 2.0/2.4 trans as the 31TH and the starter-in-back 2.2/2.5 trans as the A413. I think it makes it easier for discussion to refer to them that way.

I think the long-term pie in the sky solution would be to be able to use the 4spd auto. You can gear it to have massively more gear reduction across the ring/pinion gearset than the 3spd does, which means you wouldn't have to put nearly as much input torque to it to get the same acceleration of the van in 1st gear. Plus, there have been a few of them with a lot of power put through them and i havent heard of one breaking like this yet.

If this failure happened or should I say I discovered it at the beginning of summer I would have started my attempt to put a 4 speed run by MegaShift in my van. But since it's racing season in AZ and it's easier for me to build a 3 speed, I'm going to throw one together to get me through the winter.

[Ondonti]

Does the 31TH on 4 cylinders have the same weird bracing on top of the diff housing for a motor mount as the v6 versions? Where the old versions had no mount there, just a brace that connected higher up on the bellhousing.

All for 41TE development.

[Aries_Turbo]

Does the 31TH on 4 cylinders have the same weird bracing on top of the diff housing for a motor mount as the v6 versions? Where the old versions had no mount there, just a brace that connected higher up on the bellhousing.

All for 41TE development.

I believe they do. the 3 bolt boss, gusseted flat area on top? my sohc neon did. i bolted a bracket up there that i hoseclamped the stock O2 sensor to to keep the heater circuit happy while i sent doctored signals to the ecu from my wideband to get better mileage.

Brian

Brian

[A.J.]

Does the 31TH on 4 cylinders have the same weird bracing on top of the diff housing for a motor mount as the v6 versions? Where the old versions had no mount there, just a brace that connected higher up on the bellhousing.

All for 41TE development.

Yes they do. All the 31TH transmissions that I've seen have it.

[zin]

Just to clarify, the case that broke, was it a 413 modified to accept the 2.4, or were mounts fab'd to allow the 31 to be installed where a 413 would normally reside?

My point of curiosity is whether or not the newer design would be of benefit here or not.

Mike

[A.J.]

Just to clarify, the case that broke, was it a 413 modified to accept the 2.4, or were mounts fab'd to allow the 31 to be installed where a 413 would normally reside?

My point of curiosity is whether or not the newer design would be of benefit here or not.

Mike

I am using a straight up 31TH case for the 2.0/2.4 with the starter in the front.

[zin]

That's what I expected, and kinda feared, no factory/junkyard upgrade.

Mike

[Ondonti]

I am using a straight up 31TH case for the 2.0/2.4 with the starter in the front.

So then I am wondering if the 31TH case is worse? ~2 years ago I thought about making a scatter shield that incorporated the bosses above the diff housing that would also strengthen the rest of the case. I was thinking about that when I pulled two a670's from the JY and one was old style and one was 31TH style. Wonder how dodge deals with 3.0 a670 naming since the case changed including getting a flywheel sensor but its the same platform... (not like the death of the 2.5L).

[A.J.]

I got my case, pinion shaft, and ring gear. I also had to refriction the direct drum because the clutches were worn. Got it all back together and three days later BOOM my input shaft exploded. I wasn't even getting on it hard, I was accelerating from a red light. I didn't examine the input shaft when I took it apart since all the damage was in the diff area. Everyone I've talked to says there must have been a crack in it. Pieces got jammed in the torque converter so my 10.5" LU 3500 stall converter has to go back to Suncoast in FL for a rebuild. I'm using my 9.5" Hughes converter until I get my Suncoast one back. I just wanted to get my van through emissions, registration is due at the end of the month. Before the input shaft exploded I ran it through with MegaSquirt for the first time on E85 and got HC: 3.33, CO: 32.43, NOX: 5.57. Applicable standard is HC: 3.00, CO: 25.00, NOX 4.50. With CO high I dialed a little fuel out and put on a cat. Cats are only available in 3" and I have a 3.5" exhaust so I had to cut the ends off, open up the cat with an exhaust pipe spreader, cram in and weld a 3.5" pipe. Ran it again and got HC: 1.16, CO: 7.14, NOX 2.60.

Instead of doing any racing this year I think I'm going to focus on installing a 41TE transmission and operate it with MegaShift.

[Vigo]

Ive broken the output shaft to the first transfer gear (which is much larger diameter and shorter than the input shaft, so it should be stronger) on a stock van. There does seem to be a crapshoot factor with some of these parts. I am not sure if the 604 input shaft is any stronger, but even with two years in a trans shop i have never heard of one breaking, so maybe that's something.

[A.J.]

Ive broken the output shaft to the first transfer gear (which is much larger diameter and shorter than the input shaft, so it should be stronger) on a stock van. There does seem to be a crapshoot factor with some of these parts. I am not sure if the 604 input shaft is any stronger, but even with two years in a trans shop i have never heard of one breaking, so maybe that's something.

I've broken an output shaft at the transfer gear too. I don't think the 41TE input shaft is any stronger since the 31TH torque converter will fit the 41TE. I'm doing the swap for a couple of reasons, 1) Adjusting shift points. I don't like carburetors because of the way you have to adjust fuel but yet I have a hydraulic transmission with swapping governor weights is about the same as swapping jets in a carburetor. Right now I'm in 3rd gear by 25 mph. I'm hoping I can adjust that with a lap top with Mega Shift. 2) Over drive! Need I say more. 3) All clutch packs, no bands. Not that I've had a problem with my bands, but nobody can argue that all clutches wouldn't be better.

[Aries_Turbo]

do you know how to adjust clutch to clutch shift timing in megashift?

i thought i remember flares between shifts in brians videos.

Brian