Just seeing if anyone has done this yet. I'm wanting to go from 3.70 to 3 with my Ford 9 inch. Currently has a truetrac. I reached out to Eaton about going to 3's and they said it can't be done but this company says it possibly can be. I attached a screenshot of the company's statement. I reached out to that company but no answer. Anyone have an idea on what needs to be done to the pinion gear to make this work? I'm looking at the pinion gear but I'm not sure where it needs to be clearanced at.
I'm confused. A 3.00 gear is listed as an option with the TrueTrac. https://www.quickperformance.com/Fo...-Pinion-Gear-Bearing-Kit-Package_p_21561.html What would make this ring and pinion swap not able to be performed when it's all made for the 9"?
Certain gears won't fit certain carriers . Call Randy's ring & pinion knowledgeable staff good prices ,can't ask for more !
Yup I thought the same thing but when you talk to Eaton directly they say it won't fit and the max is 3.25.
Think I"d go with the 3.25. Its not that far from 3 and you can run a tall rear tire to make up the little bit of difference.You must be running a auto trans since manuals dont really like 3"s. An S10 T5 would deal with it since its low is well....LOW.
Yup, already have a th400 and 32 inch tall tires, can't run any taller tires due to clearance. Really need to run 2.75's preferably but still would like to use my truetrac so 3's was the next best possibility from what my research shows. Not changing the transmission, just seeing if anyone has come across this issue.
I think I'd ask Eaton just what specifically the problem is and/or the vendor you're talking to. As several people have pointed out, that limitation doesn't show up everywhere and they don't seem to offer a unit for the taller gears. Quick performance doesn't show this issue and they move a lot of these... The ability to use any gear set (along with the removeable center section) without having to buy a new diff like the GM rears is one of the reasons the 9" are so universally used. Makes me wonder if the taller gears affect posi operation negatively (a 'leverage' issue?).
funny, I'm about to head out on a 5000 mile trip in a car with 28" tires and 3.08 gears and no OD....and I think it's a "high speed" setup! Maybe you'll be fine with 3.25 gears. My guess is the pinion is too "long" on the lower number ratios, and hits the carrier. Another solution would be to run a Detroit Locker instead of the True Trac. I've had 2.50 gears on a Locker, plenty of room. And yeah, also put over 100k miles on it, although with several different ge****ts. They are streetable, despite the rumors to the contrary.
It's interesting that you ran a tall gear on a locker as Eaton shows the same 3.25 limitation for that unit. Maybe they've made a design change?
I don't know what the problem would be fitting tall gears on a locker...it's a small unit, about the same size as a Ford open differential. I can see how the True Trac might run into the pinion gear. It's huge.
I just changed out a set of 3.0 to 3.70 with a True Trac. The case had been ground at the small pinion bearing area because the True Trac unit hit there. When I got the 3.70 set up I had about .005 clearance, had to pull it apart again and grind some more.
Spoke to Eaton directly and they said 3.00 would not work and that 3.25 was the best you could do. So I just called up Quick Performance and they said they run 3.00 just fine without any clearance issue so go figure. I am going to set up my 3.00 and see what the problem might be, if there even is one. May be slight difference in the case throughout the years that may be the issue.
Thank you for that information, I will be on the look out for clearance issues in that area, that may be the solution if it becomes a problem.
If I didn't already have the TrueTrac I would look into the Locker. I may still go that route as 2.75 would be ideal but I still want a posi. Thank you for the information, I appreciate it!
Just want to follow up with this post. I just finished setting up my Ford 9 inch with a TrueTrac and 3.00 gears. No clearance issue with the carrier or case. Not sure why Eaton says 3.25 is the lowest ratio you can run with their TrueTrac but so far no issues. Hopefully this might help out the next fella. Thanks guys!
With a Quickchange there are no clearance issues with the TruTrac. Gear changes take about 15 minutes. Just sayin'
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