8.3 cummins/Allison 6 speed. How much power can it handle

Blacksdieselhp

Blacksdieselhp

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Jan 11, 2008
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Just picked up an FL70 with 8.3 cummins and 6 speed allison. Its a little weak and wanted to do some pump work, but Im not sure how much these allisons will handle. Anybody have experience with them?
 
what kind of isc year,cpl, and rated hp and what kind of allison? i work for cummins/allison west...
 
Its a 1995 truck. I'll have to get the specs off engine tag and see if tranny has tag. Im pretty sure its a 225hp engine.
 
Ashley if you can find out which series the tranny is will help,
 
Ok, got some info. Engine is CPL 1566, 275hp. The tranny is an Allison MD 3060P. The truck runs good, but drops speed pretty bad on hills and I was only pulling a megacab. I thought it would be much stronger. The tranny shifts great, but it is doing a couple of wierd things. When just cruising at certain speeds, especially 47-48mph, it downshifts and says "SERVICE" on the shifter screen. It seemd to only do this at certain speeds, like its not sure which gear it should be in. Any ideas?
 
Also, i have had this happen a couple of times. Start it up, put it in gear and it wont come out of neutral, it just beeps. Turn truck off, start up again and it works fine.
 
That tranny is basically the same tranny as what I have in my mh. They work fine behind a isl which is 400 hp and 1200 ft lbs tq. But I was warned not to go any more than that with it. You would need to get a 4000 series to go higher
 
is the isc a mechanical? if so then you can do all the same stuff we do to 12v isb's, but if its caps pump. you are seriously limited. the allison 3000 is a descent enough trans. i can check the cpl's maybe able to move up the hp with minimal parts. could find some marine cpl's...
 
Blacksdieselhp said:
Also, i have had this happen a couple of times. Start it up, put it in gear and it wont come out of neutral, it just beeps. Turn truck off, start up again and it works fine.
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My 01 sport chassis did that too when I bought it. The boards are known to fail over time at least on the Eaton 6spd. After few months of waiting longer to get it to reset and get in gear it left me stranded. Installed a new touch pad assembly shifted great. 1k for a push the button selector way over priced IMO.

Glad to see you found your truck. Turn it up till it slips than back it down some. LOL.
 
The allison can take a lot. Start with the freebie mods, like fuel plate slid full forward, timing advance, and tighten the gov springs a few clicks. It'll wake it right up.
 
Yea, I already did the pump work. Gov spring are next. Runs better for sure. It was pretty low on power. The plate was all the way back. I got an hx 50 that would fit pretty nice, lol. Just wander what the stock hg on these motors will take. Gotta replace the exhaust man gaskets as they are all leaking. Thats definately some lost power. Also been looking into the Allison Retarder. Sounds like thats a good upgrade if this tranny will accept one.
 
Those trans retarders are SOOOOO awesome! You may have to replace the tail section with one that had the retarder, but a good Alli shop will tell you, or show you what all to get.
The hx50 is an upgrade, but you may still need more fuel to make good use of it.
 
Freezingsystems said:
My 01 sport chassis did that too when I bought it. The boards are known to fail over time at least on the Eaton 6spd. After few months of waiting longer to get it to reset and get in gear it left me stranded. Installed a new touch pad assembly shifted great. 1k for a push the button selector way over priced IMO.

Glad to see you found your truck. Turn it up till it slips than back it down some. LOL.
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Yea, I stole this thing. Had to go all the way to arkansas to get it and then found out that some people that we rodeo with from Tennessee( a few hours north) just sold it 6 months ago. It needs some paint work and an interior update, but we can do all that in house. Mechanically, its very clean.
 
Stacks had to go.
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Where did you find something like that. We have been looking for something similar.
 
They are very, very hard to find in this trim. We used to rodeo in one several years ago and this is the first one like it I have seen since. I believe the conversion company was called Western Star. Not sure if they are still in business. A friend of mine has a new FL 70 he bought and had the conversion done somewhere in Colorado, but he's got over $200k in it finished. The crew cab trucks seem to be plentiful though.
 
Blacksdieselhp said:
They are very, very hard to find in this trim. We used to rodeo in one several years ago and this is the first one like it I have seen since. I believe the conversion company was called Western Star. Not sure if they are still in business. A friend of mine has a new FL 70 he bought and had the conversion done somewhere in Colorado, but he's got over $200k in it finished. The crew cab trucks seem to be plentiful though.
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I could probably handle a crewcab actually. Maybe put a box on the back for some sleeping quarters and call it good.
 
What's the exhaust now? Just a single 4"? Where does it dump? Those stax would look & sound a little better if they were 6".
The 3060 is rated at 300hp/950tq, but that's also at full weight. It'll still handle a good deal more than that.
 
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Yea, I just ran 4 inch to the rear axle and dumped it down. I wouldn't mind having some 6 or 7" stacks, but they cost WAY too much.
 
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