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I'm planning the death of my stock transmission. The 2-3 shift is soft and doesnt feel as confident as the 1-2 shift does. I don't know how much life it has left, but I plan on doing lots of long distance trips and I want to eliminate any possibility of a failure on the road. also thinking a 4 speed would be a decent upgrade over the 3 speed as far as slightly higher highway speeds and better ability to deal with higher hp from a modified 4bt.

Ive read that some breadtrucks came with the AT545 and it seems like a fairly common transmission in school buses with 5.9's. does anyone have experience with it? Would it be a good upgrade over the chevy transmission? How serious are the mods required to install it in a p30?
 

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Not sure what you are replacing, but I am assuming chevy from a P30 since you said auto. The 4L80E will bolt up to the bell housing and get you .75 OD. Mine was about $2K said and done with a full manual build up. If you go electronic is will be another 5-700 depending on controller choice and what you have to add.
 

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the at545 is still a 4 speed, but i'm pretty sure 4th is 1:1 which means no overdrive. the 4L80E is a good option.


the at545 came in some of the later p30's with p'pumped 4bt's. you will need the whole setup with the sae 3 adapter, etc.
 

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Mine was about $2K said and done with a full manual build up.
I saw you talk about the manual build in the 4L80 before. When doing this you still need some form of modulator to adjust line pressure don't you? Where did you get the valve body for the manual conversion. I have not seen one from the mail order performance companies. I would like to go to OD in place of my 475 in the future.
 

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It's a kit from transgo that needs to be installed. It requires replacing/modifying shifting rods and drilling of the valve body to modify the flow of the fluid. Yes, as I found out, you do need to modulate the line pressure. The transgo kit comes with the modulator but doesn't say that you need it (it had it's own set of instructions like it was optional but it's not, it's necessary). There are also some internal mods you can make that is included in the kit like stiffer direct drum springs and some pump mods. I've shown some of this in my build and am currently working on line pressure now. Turbos10 headed me in the right direction.

Kit: trans-go 4l80e-3
Search this in google and you'll get some hits. Look for the full manual control descriptions.
 

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Discussion Starter #6
What is the ratio of the th400 in 3rd?

I'll look into the 4l80e. Not sure if I have enough hp for an overdrive, considering the engine is still driving a breadtruck. mine barely does hills as it is.
 

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its much cheaper in the long run to go with a 727 or 47rh if you want overdrive. stronger than the chevy trans also.
If he already has the GM stuff, a 4L80E with manual valve body isn't a bad way to go either, plenty strong, and probably cheaper just because he has the gm stuff.
 

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It's a kit from transgo that needs to be installed. It requires replacing/modifying shifting rods and drilling of the valve body to modify the flow of the fluid. Yes, as I found out, you do need to modulate the line pressure. The transgo kit comes with the modulator but doesn't say that you need it (it had it's own set of instructions like it was optional but it's not, it's necessary). There are also some internal mods you can make that is included in the kit like stiffer direct drum springs and some pump mods. I've shown some of this in my build and am currently working on line pressure now. Turbos10 headed me in the right direction.

Kit: trans-go 4l80e-3
Search this in google and you'll get some hits. Look for the full manual control descriptions.
Right on. I had someone do the buildup for me, but he said it was a full day deal and he would not do it again for $2K. It works very well now that it is all finished up. I used a chevy vacuum valve to modulate vacuum to the transmission.(reminds me....I owe a PM with that part number)
 

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its much cheaper in the long run to go with a 727 or 47rh if you want overdrive. stronger than the chevy trans also.
The 4L80 can be built to be fairly strong. While a diesel is different they will hold 1000+HP gassers.
 

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So let me see if I understand this. You get full manual control instead of the trans. shifting on its own. In other words I have to shift it. For the price of a 4L80E around here its kinda worth getting the stand alone controller.

If this kit would allow the 4L80E act as a auto trans by shifting itself the it would be great.

Of course there is the possibilty I have completely misunderstood this.
 

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So let me see if I understand this. You get full manual control instead of the trans. shifting on its own. In other words I have to shift it. For the price of a 4L80E around here its kinda worth getting the stand alone controller.

If this kit would allow the 4L80E act as a auto trans by shifting itself the it would be great.

Of course there is the possibilty I have completely misunderstood this.
full manual means that yo shift it when you want to shift, nothing automatic about it. Some seem to like it, some don't.

The controller allows you to have full control of the trans, the compushift allows it all on the fly with no laptop, most others require a laptop. There were some megasquirt guys trying to make a controller for it that would be more DIY.

With a controller you can make it push button shift, or automatic like original application and tune it to your liking.
 

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I did the full manual for the cost savings mainly, but I like having full control as well. I actually dont mind shifting and enjoy being able to make the transmission shift how I want. I have never fooled with the aftermarket trans. controllers, but if they are not highly tunable I would not be happy. I worked as a controls engineer for 6 years so I can't stand for stuff like that to be half tunable which is the case with many of the aftermarket controllers. I have built an programmed a few DIY engine controllers, so I might give it a whirl on a tranny some time.
 

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Some seem to like it, some don't.

The controller allows you to have full control of the trans, the compushift allows it all on the fly with no laptop, most others require a laptop. There were some megasquirt guys trying to make a controller for it that would be more DIY.

With a controller you can make it push button shift, or automatic like original application and tune it to your liking.
There is very little feedback I've found on this kit (transgo) when surfing the net so I haven't heard anyone who had it that doesn't like it. It seems those who do have it wanted to have the control over the tranny by shifting it themselves in the first place and enjoy rowing the shifter. But, your right, it is not for everyone and depending on the setup it might not be much more to just go with a stand alone controller. Seems like I've read about the megasquirt option for a while now, hopefully it becomes another option soon.
 
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