When a torque converter doesn't have lockup it's always at a reduction. Ratio depends on the converter. Use them on garbage trucks and school busses alot.

For efficiency having the torque converter able to lock itself for direct power transfer is crucial, in my opinion.

And I'm not 100% yours isnt, I just know that model is usually not. Maybe you can get the model no off the transmission and someone can identify?

Hope this helps

 

I think you might be onto something with the converter. I can't find any promising info on a out of the box converter that locks up. I'm not a posed to having one made, but still no overdrive so what about an adapter plate a 1 ton pick up? If I went that route what would you recommend?

 

Just took her for spin, and I completely agree that the converter is my speed issue. I'm going to look into a custom converter

 

I agree completely

 

This outfit lists the specs. They say no lockup on the 500 models, and they do not show lockup in their ratio chart. That, plus the converter ratios show seem to add up to your high revs situation.

I do not think a converter is your answer. The lockup mechanism for this type of trans is much more involved than just the converter.

http://powerforce.com/PDFs/Transmiss...S_PF_AT545.pdf

 

There's no lock up convertor's for an AT545 trans.
You may want to consider changing to an MT653 that has a hydraulic lock up convertor, or the MD3060 that has electronic OD and lock up, it has a stand alone controller but some sensors will have to be added.

 

So I found this transmission on craigslist and I'm not a posed to doing a swap but will this trains bolt to my engine? Is the bell housing the same, what type of sensors need to be added? How can I tell if this has everything I need?


https://sacramento.craigslist.org/wto/5506795286.html

 

I talked to my local Allison dealer who said the swap would not do what I want. He suggested the confirm the ring and pinion ratio and go from there.

 

I disagree with the dealer in the fact that an at545 will have convertor slippage up to 2500 rpm or more where a 653 will lock the convertor and lower the rpms.
There are three sizes of SAE bell housings and not knowing what engine you have or housing size I can't tell you if the other trans will if or not.

4.56 ratio with 42" tires will run 60 mph at 2200 rpm.
2800 rpm at 60 mph with 42" tires = 5.50 ratio but your high rpm could all be in convertor slippage, IDK
Your cal of one tire rev = 2.25 drive shaft turns is about right for 4.56 ratio on car diffs but don't know if it works the same on big truck diffs.

 

I'm in agreement with you on my rear end ratio. The guy wants me to pull the drive shaft to get the numbers off the end of the pinion..... I think he's not very knowledgeable. Anyone got a number of a Allison dealer who knows what he's talking about?

 

I'm running a ford 7.8 with a at545. How do identity what converter I need, and where will I find an adapter plate if needed? I think the guy I talked to was talking through his hat, because he said it's a power issue. Its not because I can get it to spin at any rpm I want it just doesn't put it down...

 

Converter? In reading the above, I thought it's pretty well discussed that a different converter won't really help. I do see two ratios for converters in the link I posted above, but you will have to figure out what you have and if you have the tighter converter already, then you do not have a converter option.

The MT545 link says SAE #3, the MT653 link shows SAE#2.

http://www.powerforce.com/pdfs/trans...s_pf_mt653.pdf

I can't pin it down, but the 7.8 may have a SAE 2 pattern and you have an adapter on there for the 3. I think you would have to pull it apart and look at it and measure to be sure.

SAE chart:

SAE Bellhousing

Adapters:

Phoenix Casting & Machining, Inc. - SAE Housing Adapters

Regearing vs. a trans swap....decisions decisions.

 

I need to get under my 93 F-800 to see which trans and gears it has, it has an 8.3 cummins with allision and when the convertor locks up it will run 75mph at 2200 rpm.

 

So per your link the optimal converter in my eyes is the tc380 with the 1.82:1. That's dam near 2:1 is that 2 engine revs to one rev of the input shaft? If that's the case this transmission is not an option for me. I want something with 1:1 I'm waisting power if I understand the ratio correctly.

I see its a sae 2 flywheel cover. Does power force have a pdf mt653?

I don't mean to come across arrogant but I know there's a way to get 1:1 in the converter

 

You will only get 1:1 with a lock up convertor