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Durango AWD 3.70 diff swap for less? Yes!

396 Views 11 Replies 3 Participants Last post by  HEMIWOT, 
HEMIWOT
Saved around $1000 thanks to ZF parts crossing platforms.


That there is a front diff from an 06 Mercedes GL450 holding the axles. The axles are stock Durangos, I'm pretty sure every 11+ AWD Durango/Jeep GC uses the same front axles and that particularly shaped 195mm front diff pumpkin.

Jeep or Durango SRT front diffs cost between $1100-$1200 shipped. The Mercedes one cost me $220 shipped😄(I have to pay tax for online purchases). I wasn't even going to go back to AWD after switching to the SRT 3.70 (which cost about $2000, diff plus SRT axles) because of the high price of the SRT front diffs. This will help a lot when data logging and pulls on the street for the new upcoming mods. Getting her ready for the track is a process. Track days in Vegas are quite limited till September.

Unfortunately at the moment I have not found a practical less costly way to do a 3.70 or 3.90 rear diff swap from the Mercedes. It can be done relatively cheap but I would not recommend it for high torque RWD applications, as it uses the 195mm ring gear and thinner axles. For a relatively stock motor it would probably be ok. Only issue is the drive shaft has a 3 bolt connection. Not really sure yet what it takes to change that.

The whole 3.70 or 3.90 195mm ring gear AWD package including the 195mm rear axles, would be around $700 or so, if you were willing to change out the drive shaft connection. Not bad for a big low end torque gain to the wheels over the stock 3.09 differentials.
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awehlage
Fantastic!!

What did you have to change in your tune to accept the 3.70 front and rear differential swap?


My build thread - 2016 R/T - awehlage’s build
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HEMIWOT
Nothing. Not necessary. Just redo the same tune and let the PCM/TCM learn the shifts again.
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R
So basically, get the 3.70 front end from the Mercades and then the 3.70 rear from the SRT and $save vs. what you would have had to have paid doing "Mopar" ZF front bits too?
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HEMIWOT
r4nd4llm4n said:
So basically, get the 3.70 front end from the Mercades and then the 3.70 rear from the SRT and $save vs. what you would have had to have paid doing "Mopar" ZF front bits too?
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Exactly. The SRT front diffs are expensive. The Mercedes ones are cheap, even though they're exactly the same internally.
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HEMIWOT
r4nd4llm4n said:
So basically, get the 3.70 front end from the Mercades and then the 3.70 rear from the SRT and $save vs. what you would have had to have paid doing "Mopar" ZF front bits too?
Click to expand...
Unfortunately the Mercedes rears don't use the same size ring gear or axles, making them weaker for a high performance type of build.
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HEMIWOT said:
Unfortunately the Mercedes rears don't use the same size ring gear or axles, making them weaker for a high performance type of build.
Click to expand...
Yeah the V8 rears in these trucks is the 230mm unit. Also, it seems that minor case differences would become major issues as you noted was the case even when trying top use a HC/Trackhawk housing in a SRT or R/T trimmed truck?
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HEMIWOT
r4nd4llm4n said:
Yeah the V8 rears in these trucks is the 230mm unit. Also, it seems that minor case differences would become major issues as you noted was the case even when trying top use a HC/Trackhawk housing in a SRT or R/T trimmed truck?
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Hellcat/Trackhawk rear diffs are expensive too. But they won't fit in the SRT/RT without welding and grinding work or a whole new cradle.
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HEMIWOT
r4nd4llm4n said:
Yeah the V8 rears in these trucks is the 230mm unit. Also, it seems that minor case differences would become major issues as you noted was the case even when trying top use a HC/Trackhawk housing in a SRT or R/T trimmed truck?
Click to expand...
SRT Left: Trackhawk/Hellcat Right:
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HEMIWOT said:
SRT Left: Trackhawk/Hellcat Right:
View attachment 127155
Click to expand...
Wow, these are mad different. The two front bolts that appear to be vertical through the bushings? Not present in R/T and SRT applications? But present in HC/TH? What, if anything, secures the front of the diff on the R/T and SRT? I saw that for the TH, they made some type of additional brace on the rear of the rear diff to prevent wheelhop? THis must be a killer on the SRT application esp. if in 2wd mode?
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HEMIWOT
r4nd4llm4n said:
Wow, these are mad different. The two front bolts that appear to be vertical through the bushings? Not present in R/T and SRT applications? But present in HC/TH? What, if anything, secures the front of the diff on the R/T and SRT? I saw that for the TH, they made some type of additional brace on the rear of the rear diff to prevent wheelhop? THis must be a killer on the SRT application esp. if in 2wd mode?
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Not for wheel hop. For the rotational force to the diff under hard acceleration.

By comparing pictures of the two different cradles I'm pretty sure the SRT and RT cradles could be made to fit the TH/HC diffs. Would require welding some spacers and removing the stock front hanger.
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HEMIWOT
It's official. Just installed the Mercedes 06 GL450 3.70 front diff. Exact fit as expected.

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