Question regarding "thick" vs. regular rear gears

[tobijohn]

Are the aftermarket "thick" 3.54/3.73 gears that are used in 2 series Dana 36 any stronger or weaker than the 3.54/3.73 gears that would be used in a 3 series one? I've got 3.07s now and am thinking of picking up another diff to have rebuilt with 3.54s in advance. Should I look for a used 3 series or will a 2 series with those gears be no worse strengthwise? I've also gotten the impression that Precision makes a better quality gear than Richmond. TIA...

 

[Ken]

That subject recently came up for me - I just had my rear end rebuilt and finally got it back on the road yesterday. I used Precision gears this time around, but I can't tell you the strength differences between the different Dana series. I couldn't really get a straight answer myself when I asked the question about the differences in the series.

Hopefully, we'll have someone explain the benefits of each series here soon.

 

[tobijohn]

That subject recently came up for me - I just had my rear end rebuilt and finally got it back on the road yesterday. I used Precision gears this time around...

Thanks Ken, you mentioned "this time". If you don't mind me asking, what happened that the rear needed a rebuild and what made you decide on Precision? Thanks..

 

[Ken]

I installed 3.73's a few years ago. The shop evidently did not entirely rebuild my old unit as I thought - they just changed the ring and pinion, nothing else as far as I can tell, although judging from the cost on my bill, it should have reflected it was a newly-remanufactured unit.

The unit worked fine with the stock engine for the next year.

In 2002 I built my current engine, a 417 cid small block that should be making around 450 or so rear wheel horsepower (if I ever get this thing dialed-in).

The third member gave out on me about three weeks ago and started howling like mad. Luckily I was close to home and prevented any major damage - just hurt the ring and pinion.

I had Unitrax rebuild the unit this time, so once again I simply placed my trust in someone else's hands. The feedback from people here at the CAC who've used Unitrax, along with the opinions of some people I've spoken with at local cruises, the comments I found on the Internet (mainly off-road vehicles and trucks), plus the fact they have 20 years experience in the business adds up to indicate a satisfactory outcome. :cool

I did ask him about the differences in the series of Dana carriers but didn't really get an answer. My mechanic though, thinks it's mainly in the case design, for what that's worth.

However, we all know that being a hot rodder carries with it the possibilty of parts breakage at any time. Good luck!

 

[tobijohn]

Thanks again, Ken. If you don't mind, approximately how much did they charge you to rebuild it? I'm assuming you R&Red the diff yourself. Also, I'm a little unclear as to whether you reused your original 3.73s or had new Precision 3.73s as part of this last rebuild. Thanks...

 

[Ken]

All new parts this time, to the tune of $570.62.

I'm pretty sure they used Precision gears, although they utilize U.S. Gear, as well as Auburn and a few others for trucks.

And yes, I did all the labor myself, and I am still sore as hell from doing it. Gettin' too old for this stuff! :L

 

[tobijohn]

All new parts this time, to the tune of $570.62...

Was that just the parts bill or does it include the install/setup labor as well?

 

[Ken]

Parts, labor and setup included. The full story with pictures can be seen HERE.

 

[tobijohn]

...The full story with pictures can be seen HERE.

Thanks again, Ken...

 

[tobijohn]

FYI:

I emailed Justin Abbott at Zip Products (who sets up the 3.54/3.73 Vette diffs that they sell) and this was his response:

"The ring gear makes no difference in the strength. That is not where the issue is on a D36. The issue is with the housing, and what happenes under a high load it the pinion actually pushes the carrier backwards instead of spinning it."

 

[Ken]

"... what happenes under a high load it the pinion actually pushes the carrier backwards instead of spinning it."

That's exactly what happened to Mike's D36, but it also sounds like what happened to my D44.

 

[tobijohn]

Well, I've yet to hear of anyone breaking a 3.07 Dana 36 and that includes guys with 396 motors. However, as soon as the 3.54 or 3.73s go in (2 OR 3 series), it seems to just be a matter of time. And that's not just built motors either - stock LT1s with 2400+ stall TCs and 3.54/3.73 gears are breaking diffs too....