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What Tranny

3K views 29 replies 7 participants last post by  mopar969 
#1 ·
Okay so my 93 daytona that i drag race came with a 604.I have read threads where you can build the 604 up. However most opinions tell me to swap it for a 670.Where can i find a built 670 to race with at a reasonable price.

Also I found out the the internals of the 670 are the same as the 413. To go faster with the 604 I was going to do the 4.28 pacifica ratio gear swap that Vigo has helped me with. Is there a gear ratio swap for the 670?

My main question is that if my 604 only has 67000 miles on it and runs fine maybe i should stick with the 604 and not swap to the 670????
 
#2 ·
Below is a chart from The Dodge Garage, it's for factory A-413's combos but is applicable to A-670's. I read some Neon guys have had custom ratios built for the 3 speeds, but are very pricey.

I've replaced Caravan A-604's with A-670's in the past and it's an easy swap, so I'm thinking the Daytona would be also. No need to hack anything up so it would probably be good to find a spare to swap and try when the A-604 fails.

Thanks
Randy




2.60 => 0.91 transfer and 2.86 ring
2.78 => 0.91 transfer and 3.05 ring
3.02 => 1.06 transfer and 2.86 ring
3.22 => 1.06 transfer and 3.05 ring
3.50 => 1.22 transfer and 2.86 ring
3.72 => 1.22 transfer and 3.05 ring
 
#4 ·
The a670 is hydraulic so that gives you full control over line pressure, shift speed, and shift points with the right modifications of course.

The 41te leaves you with 5200rpm shift points, slow shits, and no control over anything really. But with a few valve body mods and a stall converter it can become acceptable for drag racing.
 
#6 ·
Not to be rude but that's all wrong. :p

Pretty much ALL but the earliest 3spds (or later Neon stuff) came with the 3.02 FD ratio. The 2.60FD is only attainable by mixing factory parts that never originally came together. Plus, it's the EXACT opposite of what an n/a 3.0L 3000lb drag car would want. Some early k-cars came with either 2.78 or 3.22 FDs. ALL 670s were 3.02FD stock.

The 604 with the 4.28 ratio has a HUUUUUUUUUUGE gearing advantage over even the shortest geared 3spd combo. And that becomes more and more important the slower the car is. A 3.0/auto daytona is an 82-86mph trap car depending on bolt-ons. It needs all the help it can get. The 3spd doesn't hold any real advantage until you are making enough power to break a 604 and spin slicks from 0-30mph where short gearing isnt helping you anymore. Even the strongest documented n/a 3.0 12v build has never gotten to that point. They put multi-year warranties on 604s behind more powerful engines in heavier cars. The other possible way that the 3spd holds an advantage is having full manual control of how it operates. You ONLY have to learn how an automatic transmission works and how to rebuild it and be willing to spend a shit load of time futzing with it to take advantage of that! Easy peesy. And this engine will never go past 5800 rpm without a modified ecu. A 3spd would not change that.

To me, it's crazy to suggest the 3 spd for an n/a drag race build.
 
#7 ·
Awesome thanks vigo. I think the big thing is that the 3speed is great for the 4cylinder engine. But for the v6the 4 speed is the way to go besides even after adding boost my plan for this car is to reach a 12.50-12.80 max. Which I think is doable with the 4speed.Vigo what do you know about getting the tcu flashed for a Plymouth prowlers tcu?? Maybe you can't just flash it and you need the whole tcu? The only thing I will miss with the 3speed is banging manually through the three gears but I will get over it.
 
#8 ·
I believe it was mostly mentioned as a spare backup when the 604 blows up, not a recommendation, or if he decides to turbo it.

I'm not sure if he's bracket racing or not, but if he is, it's more about consistency/reliability than the fastest times.

Angelo Taylor won plenty with his N/A Omni (MATCHBOX), he was so consistent, not fast !!

If he was an experienced transmission guy he probably wouldn't be asking these questions.

There's no doubt, when you help him build the Pacifica geared 604 he'll be faster than with a 670!!

Thanks
Randy
 
#9 ·
I like the a670 because I know how to rebuild it and the parts are cheap. That's the main reason why I would pick the a670 over the a604. I don't have any experience with the electronic 4-speeds other than my dads old 98 intrepid and that trans broke with 110k miles. I may be a bit biased. If you are happy with the a604 then stick with it. My van will break the tires loose at any speed attainable in 1st with a 3.02 fd if I go WOT and I don't think I can get bigger tires on it without spacers(225/70/14). That's at 7psi with the m62. Granted a turbo should get better traction because of lag but I wouldn't want the shorter gears the 4spd offers.

On the other hand, I have broken just about every part in my 3spd at one time or another. The a604 seems to be stronger in terms of the hard parts and as Vigo said it was put into cars with more weight and horsepower than any a413 type trans ever was. I think the main factor is whether you want to go with the tried and true 3spd with lots of documented success(and failure) or be a guinea pig with the 4spd and possibly have something better than the other people who are too afraid to try it.

If there was a way to "tune" the TCM or easily rig something up to give full control of the shifts I would snatch up an a604 in a heart beat but the way the trans is designed a relatively complicated system(like the stock one) is required.

As for manual control what about autostick? It wouldn't be that hard to wire in a TCM with autostick would it? My dads intrepid had it and it was actually pretty cool. I remember it shifting better when I used the autostick especially 3rd.
 
#10 ·
The problem with the 4 speed is if you had a heavily modded 3.0, you might never even want to hit below 5000 rpms.
The way the transmissions shift stock, it motivates you to not do serious engine modifications that all move the powerband to the right.

I do agree that on a very slow car, the a604 gearing could be a huge advantage. What MPH would a 4.28 ratio transmission top out at in 3rd gear?
 
#11 ·
Im almost positive the 4.28 gear set requires removing material off the case too fit the output gear, and the shims have to be reset for proper bearing preload. Should prove difficult with the trans still in the vehicle.

Max speed in 3rd with the 4.28 gears should be about 85 mph.
 
#12 ·
Assuming stock 5800rpm rev limiter and 23" slicks, a 4.28FD 604 would hit 5800 rpm at 93 mph. So it's pretty much ideal for this low-power drag car.

If the car goes faster, even with 'just' the 6200 rpm rev limit of the 5spd ecu, it will hit 6200 rpm at 99mph. 106 if you go to 24.5" slicks. 111 if you go to 6500 with 24.5s.

It's not really possible to change the ring and pinion of a 604 without dropping the trans. Technically you could by dropping the k-frame, but by that point you aren't saving any effort vs just removing the transmission.
 
#13 ·
How high can you take 3rd and will it force you into 4th gear or can you prevent that?
Going slightly larger on the tire size is a nice option. those shorter 23" tires plus tall gears would probably equate to a very fun E.T. for a low power car. I would think mid 14's if I did junk tires 15.5@87-88mph in a mild bolton 3.0 Spirit with stock a604.
 
#14 ·
My screwing with my 3-speed on the street against my friends, the long 1st gear when shifted manually was always my advantage. Not sure what it would have ran in the quarter, but against cars that should have walked me, the gearing/torque of the 3.0/3-speed combo almost always got the win.

That being said, the 604 offers quicker launches, and reliable shifts, so for a bracket racer, I would stay that route.
 
#15 ·
Thank you everyone so much so based on what 6g72 acclaim said the 604 is more reliable and suitable for my needs of bracket racing due to its consistency compared to the 3 speed 670. However, if I want to ad boost in the future and have the car in the 12 seconds would the 604 with 4.28 gears hold up. I have read threads on here and the other turbo forum that describe how to build these trannys up.

So, is it realistic for this 604 Tranny to be consistent and run say a 12.50 in the 1/4 mile with boost.
 
#17 ·
Our spirit with the 604 shifted at 5500, if I held it manually it would still shift @ 5500. Our Voyager 3.3L/604 is the same thing, 5500. :bang head

That being said, our Stratus we used to have 2.7L/604(variant) would shift @ 5800 itself, shifting manually it would allow it to hit the rev-limiter once or twice before shifting (which led to an awesome fireball on the shift):dancing:.

I wonder if it is possible to get that trans tuning on an older 604? :shrug:
 
#18 ·
How high can you take 3rd and will it force you into 4th gear or can you prevent that?
On the older TCMs there is no early 3-4 upshift and putting the shifter in 3 will let you bounce off the rev limiter without going into 4th gear.

Im im sure the 1st gear clutches and the rest of the planetary will hate you
All of the clutch packs and planetaries are before the gear reduction of the transfer gears and ring/pinion, so the torque they see will not change.
 
#21 ·
Okay so it looks like there is no gain to go to the 670 except being able to manually shift. Also I like the idea of running in d3 as this is what I have done this pass racing season and I noticed slightly better results with being consistent. Although it would be awesome to manually shift I think the decision to stick with the 604 is best for my needs.thanks everyone and if someone feels otherwise let me know as I am always open to opinions.
 
#23 ·
The late-model 3.0 van's 670 has the strongest parts. The 670 can be had in about everything that had a 3.0, Spirits, Acclaims, Caravans, Voyagers, etc.
 
#26 ·
Also if I do switch to a 670 i believe that a kick down is needed is there any thing else I need in order to swap? Also fwd performance has a manual valve body for the a413 will this work in the 670 I am going to assume yes. Do they sell a reverse manual valve body though??
 
#27 ·
The valve body will work but it might not have the parts for the lockup function. If you decide to get one and lockup is important to you, make sure it's a lockup VB. A non lockup VB will work fine with a lockup trans. The lockup will just not function.

If you want to, you can convert the VB to full manual yourself pretty easily. I did it and it works great. I posted about it in this thread http://www.turbododge.com/forums/f4/f22/562906-a404-413-415-470-670-etc.html. If you drill the hole to make lockup work in all gears be careful of the size. If you make it too big and raise the pressure enough, the lockup will be stuck on.

I have a cheetah reverse manual valve body and I like the one I made better. The cheetah one has a soft 2nd-3rd upshift and no lockup. Someday I will go through the cheetah and figure out how it works like I did with the stock one. Maybe I can make it better. It will take a long time to go through it though.
 
#28 ·
Wellafter goingtolook at the670 alocal junkyard had thetranny was inpieces but they did have the 604 stuff I needed sopul;led thetrigger andI amgoing withthe 6044.28 gear swap. Questions I got are:

1. Even after I put boost to the car that 4.28 ratio is huge!!! So if i go with this trans can it handle boost cause I have seen threads where people buildup these trans.

2. Also if the pacifica trans has that gear ratio why cant I do a complete tranny swap?? Maybe the gears in the daytona are better to help me go faster??

3.Lastly, how do I know if I have the 4.28 gears inthe tranny deos somoneknowthe teeth count? Thank You!!!!!!
 
#29 ·
1.Not many people have done it. It may hold up it may not. Some people have gone very fast with the a604 and claim it can handle a lot. Some claim it's junk(I tend to think these people don't know what they're doing/talking out their ass). Some people think the clutches won't last long. I say try it. If it works out and you document it well it will be a good step in the right direction. A604s are plentiful and there is an a604 case for just about every engine Chrysler ever put in a fwd car.

2.You can't swap the whole trans because the bellhousing is different. You might be able to use the internals from the pacifica trans in your 3.0l case though. I'm sure someone on here knows about that.

3.:shrug:
 
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