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GEARS: 3.25 vs 3.40? Which would you choose?

6

67resto-coupe

Member
Considering replacing the 3rd member on the stock rearend of my '67 notchback. Currently running peg-leg 2.79. Late model 5.0 motor (NOT Coyote), GT40P heads, E-Cam, headers, etc, etc...pretty peppy motor. C-4 trans with a TCI Streetfighter torque converter and a B&M shift kit. TCI box doesn't recommend going over 3.23 gears, but I'm tempted to go 3.40. Only driven to work 1x or 2x a week and it's about a 30 mile round trip on the highway. Should I heed TCI's recommendation and go with 3.25 or should I jump to 3.40? Found a guy on eBay, tj1149 (or something like it) that sells Trac-Lok, 4 pinion, 3rd members for $825 and $60 shipping. I think I read a post on this forum about folks who have had luck with this vendor. I think either gear will wake up the motor, but can't decide.

Thanks for your help.
-Jeff
 
I wonder if there is some misunderstanding on the not going over or higher than 3.23:1.... usually higher gears are nummerically lower (3.0 / 2.79). My understanding on torque converters with a higher stall speed is that you typically need lower gears to keep the torque converter engaged at speed as the slippage from running at continuous lower RPM generates too much heat. You might already be in that bad zone with the 2.79. The difference between the two gears ratios at 60 MPH is only about a couple hundred RPM (depending on tire size too). I'd lean towards the 3.40 for that type of driving too.
 
Is most of your driving city of highway? If highway go 325. City 340 is a lot more fun. I have 355 is my 68. Whines a lot on the highway.
 
"67resto-coupe" said:
Found a guy on eBay, tj1149 (or something like it) that sells Trac-Lok, 4 pinion, 3rd members for $825 and $60 shipping. I think I read a post on this forum about folks who have had luck with this vendor. I think either gear will wake up the motor, but can't decide.

Thanks for your help.
-Jeff
Click to expand...

I believe that is who I bought mine from. I have a 3:73 behind my T5. Fun in the city. 5th seems to bog down on the highway, probably should have gone 3:55.
 
Without overdrive John is right about highway driving. I have run a number of different ratios in my car. The 3.25 I currently have still feels like I need another gear at highway speeds!
But I will say the 3.40 or lower will be a LOT more fun to drive around town with a C4 and the higher stall converter.
 
I have 3.25's with a toploader and 24" tall tires. I run at ~3300rpm @ 70mph. If you're going to be driving on the freeway regularly, stick with the 3.25's. Otherwise, go with a lower gear set to optimize city driving.
 
I would go with 3.25 if I did not have an OD tranny. I purchased my rear end from TJ and have mixed feelings. My rear end whines while under a load but is quiet while coasting. I think it will have to come out and have it adjusted. He offered to do it for me but I would need to mail it back to PA and pay for shipping. It would be cheaper to have it reset locally or teach myself how to do it.
 
"janschutz" said:
Is most of your driving city of highway? If highway go 325. City 340 is a lot more fun. I have 355 is my 68. Whines a lot on the highway.
Click to expand...
You shouldn't be hearing any "whining" regardless of speed. Sounds like your set-up is off a bit.
 
as far as gears whining, i've found out one thing. if the gearset is a richmond, they are gonna whine, no way around it, they are noisy. pop had a 3.50 trac-loc 9" in the currie rear in his 38 p/u. he pulled it out numerous times & had people look at it thinking it needed reset due to the whining, but it was setup perfectly. the concensus was that the richmond gears are noisy & you just have to get used to it or switch out the gears.
 
I was wondering if it was the gears. IIRC TJ used Yukon gears on my car but I can't confirm. I was browsing around and saw some gears from Larry's Ring and Pinion that are marketed as "Quiet" gears. I have been thinking of replacing the gears if they are setup properly. I have also heard aftermarket gears are just noisy when compared to OE gears.
 
thats what i finally did with his. found a really nice chunk with 3.50 gears at pull-a-part & swapped out the chunks. the new one is only a single side, but at 76 yrs old, he isn't doing too many burnouts these days. i've got the trac-loc with the richmond gears here. figure i'll stick it in a project here one day that has an engine that will drown out the gear noise. my hearing has been messed up for about 20 yrs, so i don't pick up certain tones too well.
 
So, did some calculations, looks like the jump from 2.79 to 3.25 will add around 400 extra RPMs (2500 - 2800). Then the jump from 3.25 to 3.40 is an additional 131 RPMs (2800 a 2900). Seems like it'd make sense to go 3.40. if I'm already going to be paying a penalty at 3.25 then I may as go the extra and probably enjoy it a bit more. :)
 
Yukon gears are usually pretty quiet. Richmond gears do generally have some whine to them. I sell Randy's R&P products from time to time, and the guys at Randy's are always good at giving me a heads up on which gear sets may or may not make noise. Cheaper gear sets aren't lapped as well, may not be lapped as a set in the first place, may be made of cheaper metal, etc.
 
"tarafied1" said:
But I will say the 3.40 or lower will be a LOT more fun to drive around town with a C4 and the higher stall converter.
Click to expand...

:stu

I have no idea what I have (somewhere between 3.73 - 4.11+) in my '66 w/ large stall converter and although driving on the highway sucks serious donkey butt, it's a hell of a lot of fun to drive in town! :thu
 
Serious Donkey Butt Sucking? I need to think about that...... Butt meanwhile, if you are going to keep the C4, then going 3.40 is not much different than 3.25.

If though you end up doing a lot of 70+ mph driving like me, you might consider an AOD. Then you might consider 3.55 - 3.70 gears.

No matter what, what ever you do, it's not set in stone allowing you to change this or that whenever you want, financially speaking of course.


TapaYakin' from my iPhone
 
3.40 - I'm going that route. Decided. Just got back from a short drive and was listening to the rpms at 70mph...I typically drive 60-65 anyway and more surface streets on top of that. If it comes down to a trans change, I'm considering AOD or will look into Gear Vendor O/U, too. Thanks for all the replies.
 
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