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Discussion Starter #1
Hey guys, I could really use some help. So I put a v6 rear end in my 2005 chrysler 300c. I thought that would be the hard part. You guys who have changed axel ratios, which programmer did you use to correct the computer, or how did you make it all happy? I tried a hypertech speedo tool but the car wouldn't stop going into limp mode. Hypertech finally told me that their programmer doesn't talk to the abs system that is tattling on me and putting me in limp mode. I bought a diablosport predator 2 and tried to program the new gear in the quick options and that didn't work. I set back to factory and tried within the tune settings and same problems. When I clear the codes and it runs normal briefly the gear changes are smoothed out but by the time I hit fourth gear the abs system tattles on me and I'm back in limp mode. I tried other gear ratios, they made the shifts harsher, so I think the programmer did something for me, but it also must not talk to the abs. Diablo sport is looking into it, but I need to get it fixed. It's been down for weeks now and my wife and I need our second vehicle back. If there's a fuse I could pull to disable the abs and get the car to at least run for now short term till I can get it fixed right, I'm pretty desperate. A friend also suggested I ask if the abs modules are cross compatible. Maybe I could get one from a v6 car with my ratio and it would talk to the other modules in my V8 car and make them happy? Oh yeah I went to my local chrysler dealer. They can change tire size but not the pinion ratio in my abs system. Also no matter what gear I tune too, the speedo stays the same according to GPS, so I'm afraid I'll loose it if I disable abs, but again I'm desperate at this point.

I bought the v6 rear end cause it was 250 bucks brand new, not really for the lower gear, just cause things are super tight right now. I'm waiting on a refund from hypertech and I had to juggle some bills to buy the diablosport tuner and I'm out of money and out of credit of there's any fuses I can start yanking to get a driving car I would appreciate any help or advice you guys can give me.
 

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Not to ask a stupid question, but you kept the original 300C rear ABS sensors, correct?
......and axles/hubs?

If you changed any of that investigating ABS Sensor part numbers, tone ring differences, etc. If all this is original, both the Superchips and Diablosport Tuners differential gear ratio change programs have worked, without issue, on my LX's.
 

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......and axles/hubs?
See, that's the thing. I know that guys with the 42RLE who changed rear ends ran into a similar problem. Aftermarket tuners apparently can't change the axle ratio on the 42RLE's TCM. I don't know if that's related to his ABS issue, but it makes sense to check first to see if his ABS system is all original to the car.
 

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Yes, same axels and hubs. The center piece is all I changed.
Great! I can't think of any reason the Predator can't change the axle ratio. Usually their tech support is pretty good, but while you're waiting, put up a post here and see what shakes loose.

Did they have an option for the exact gear you have, or did you have to approximate?
 

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Discussion Starter #7
They are original.

Also with the hypertech it would fault and go into limp mode on second gear, even first. With diablo it likes to make it to fourth before it throws codes.

But the center diff piece is all I changed.
See, that's the thing. I know that guys with the 42RLE who changed rear ends ran into a similar problem. Aftermarket tuners apparently can't change the axle ratio on the 42RLE's TCM, I don't know if that's related to his ABS issue, but it makes sense to check first to see if his ABS sensors are all original to the car.
 

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Discussion Starter #8
Great! I can't think of any reason the Predator can't change the axle ratio. Usually their tech support is pretty good, but while you're waiting, put up a post here and see what shakes loose.

Did they have an option for the exact gear you have, or did you have to approximate?
My gear is now a 3.90. Their tuner does 3.92. I thought that was ball park enough, but maybe not? What do you think?
 

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That should be roughly within the range of normal tire wear. But I still think that the folks at DiabloSport need to explain why this shouldn't work on your car.
 

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Discussion Starter #10
Finally got my account for their forum activated.

I talked to their techs via email, and some friends and more forum digging. I'm starting to think that when they pulled my axels and hubs appart, that the tone or reductor rings or whatever got messed up. They say they get fragile over time and are made of rubber and magnets so they could have just fallen appart at 15 years old.
 

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And the tone rings didn't throw a code? That's crazy. But it absolutely makes sense otherwise.
 

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Discussion Starter #12
Hey guys, after talking to Diablo sport tech support and more digging and talking to people I'm thinking that tuner might be working right. Maybe the abs tone rings got messed up when they pulled my axels and hubs appart. Could cause the codes, and the esp lit up on one of my test drives. I'm going to check when I get home but what do you guys think? I wonder if that is the issue if I can drive it home out of limp mode by temporarily dissabeling the abs system.
 

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Well, like I said, I'm surprised that the tone rings didn't throw a specific code, but otherwise, yes, it absolutely makes sense.
 

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Discussion Starter #14 (Edited)
Well, like I said, I'm surprised that the tone rings didn't throw a specific code, but otherwise, yes, it absolutely makes sense.
The weirdest part is how the speedo is unaffected by anything. Think it corrects itself by the wheel speed? Assuming the front speed sensors are still fine?

Sorry carl, I got confused what I was replying too and kinda double posted, lol
 

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Unknown. At least tone rings are cheap, you can go ahead and swap them out. Don't forget to clean up the axle mating surface, and a dab of silicone grease will help ease them on.
 

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Discussion Starter #16
Unknown. At least tone rings are cheap, you can go ahead and swap them out. Don't forget to clean up the driveshaft mating surface, and a dab of silicone grease will help ease them on.
I thought they went on the axels at the hubs. Imma have to read some more.
 

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Discussion Starter #18
Ha...they sure do! Corrected.
Hey Carl, Could I bug you one more time?

I'm home now for five days starting today. I went ahead and ordered the tone rings, should get her Wednesday, give me just enough time to drop it at the shop and have it to leave Thursday night to go back for my next ten day hitch. Fingers crossed it fixes it. Just want your thoughts one more time if you don't mind. Maybe there is something I missed.

Before the diff was swapped everything worked great and the car was in top shape. I took it to a dealer a couple months previously to have the trans flushed and changed. Since it was a 15 year old car they flushed with fresh fluid and no cleaning chems that might eat at the potentially worn clutches in the trans and the tech showed me the old fluid. It was pretty dark, but he thought it was in fine shape and should continue to work fine. It seemed to be working fine, and still does.

Couple weeks ago I had that hypertech tuner and It wouldn't stay out of limp mode, kept saying second gear ratio was bad and I'm not sure what all else. I can't remember now.

Over a week ago when I tuned it with the diablosport tuner and test drove it, It shifted fine but would stop when I reached fourth gear and then it would go into limp mode. I might be able to go 70mph in 4th, but then after i stopped to turn around I was limited to 40mph and 4th gear and it gave the code for bad ratio fourth gear. I cleared codes and drove a dozen times. One time instead of the gear codes, it said improbable wheel movement and the esp light came on. If I selected other gear ratios in the tuner it might shift kinda hard, and It might fault on other gears than 4th.

I'm home now. I programmed it again, and cleared codes and drove it and cleared codes over and over looking for varying results. Now it won't even leave outside of limp mode and it consistently says gear ratio one and gear ratio two are incorrect. But being in limp mode it's not winding out the gears, it's just gently accelerating and gently shifting. I can barely tell it's shifting gears, but I can just barely and it goes all the way to fourth. If I drive long enough and turn it off and on and drive without clearing the codes it will give me the generic tcm code, probably because I'm driving with wrong gear ratio. Also when, in fourth the rpms match the speed i should be going for the rear end i have installed, and i don't feel any slippage at all. What throttle it gives me responds crisply, I can tell if i get it out of limp mode it's going to be viscious with that 3.9 axel ratio.

My computer programming / car enthusiast friend tells me with software there is a hierarchy of conditions and which code to throw for what, if then kind of statements. It meets the conditions for this code it throws it, maybe a slight difference though might throw a different code for the same physical problem.

So going back over what the car has gone through between working, and now, not working. The axles and hubs were pulled and control arms unhooked and differential swapped out. It's either one of those things got messed up, or the trans just decided to stop working right literally over night, without showing any obvious driving symptoms, or the tuner isn't tuning it right because of some odd thing about my specific car. I bet if my car is an odd model year, diablo would know about that issue and be able to tell me in the many phone calls and emails I've exchanged. I really strongly doubt its the trans, it was super fine and still seems to be. I suspect the tone rings are still there and giving a signal, but they are damaged and giving a weird signal that the car thinks is legit, but showing the trans slipping so it says the gear is bad, and only once showed a bad wheel speed, cause it's just good enough to think it's good.

Wonder if I sound insane, or it seems plausible to you? I'll find out for sure in a few days, but maybe there's something else you can think of that I should look at, or a better way to test something?

P.S. I tried pulling different fuses to disable abs, apparently you just can't turn it's whole system off. Anything that would disable wheel speed sensor would just make the car not run, or shift out of park or whatever.
 

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I'm kind of tapped out on this issue, Greg. I've never done a gear swap on an LX, so much of this is theoretical for me.

With that said, it sounds to me like you have the right diagnosis. Other than the fact that the tone rings aren't throwing a specific code, damage to them while swapping out the pumpkin makes perfect sense. If the tone rings are damaged, it would explain why no amount of adjustment with the tuner helps and why Diablosport is baffled. If you Google "dodge charger gear swap" without the quotes, I think you'll find that, electronically, all that most guys do is use a tuner to correct the ratio and they're done.

So while I understand and appreciate your frustration with only having a limited amount of time at home and having to wait for parts and so on, I think you're on the right track.
 

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Discussion Starter #20
I'm kind of tapped out on this issue, Greg. I've never done a gear swap on an LX, so much of this is theoretical for me.

With that said, it sounds to me like you have the right diagnosis. Other than the fact that the tone rings aren't throwing a specific code, damage to them while swapping out the pumpkin makes perfect sense. If the tone rings are damaged, it would explain why no amount of adjustment with the tuner helps and why Diablosport is baffled. If you Google "dodge charger gear swap" without the quotes, I think you'll find that, electronically, all that most guys do is use a tuner to correct the ratio and they're done.

So while I understand and appreciate your frustration with only having a limited amount of time at home and having to wait for parts and so on, I think you're on the right track.
thank you sir
 
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