3.45 Differential install

Drivetrain discussion including Transmission, Differential, Driveshaft, and related items.
Gerome
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Re: 3.45 Differential install

Post by Gerome » Sat Oct 18, 2014 5:08 pm

Please post some video if it is at all possible ! Some of us have to live vicariously through you lol .

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greasychevy
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Re: 3.45 Differential install

Post by greasychevy » Sat Oct 18, 2014 10:43 pm

If i can get it in and get to the track I will try to make sure there is video! even if its camera phone.
2011 9c1 Hugo Blue

Gerome
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Re: 3.45 Differential install

Post by Gerome » Sun Oct 19, 2014 3:14 pm

Thats what I'm talking about ! Thank you very much looking forward to the video .

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Bowtie Junkman
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Re: 3.45 Differential install

Post by Bowtie Junkman » Thu Jul 16, 2015 8:44 pm

Sorry for being late to the party on this thread ....

But am I correct in my thinking from this post that the Camaro diff is a DIRECT bolt-in replacement? Mounts, driveshaft, axle shafts, electronic connections ... ALL the same?

I know you did a bushing upgrade, and from the pics the Camaro diff looks a bit bigger in overall size ... but from reading this thread it seems to me to be a direct bolt-in with no other mods required (other than recalibration for gear ration) ?????

If so, I'm excited ...

Pursuit
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Re: 3.45 Differential install

Post by Pursuit » Fri Jul 17, 2015 1:39 am

Yes, sir! All a direct swap. It does look bigger as the body is larger, but the mounting points are dimensionally the same. I just reprogrammed for the gear ratio change.

Maurice
Maurice Sheil

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2011 Caprice Phantom Black 9C3
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1995 9C1 Caprice
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orgdnr
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Re: 3.45 Differential install

Post by orgdnr » Sun Jul 19, 2015 4:18 pm

This was a great upgrade and woke my car up! There is a guy in Va. That has a pallet of new units $900 shipped. He is a lubricant manufacturer for GM and they are left over from beta testing.
Dave
Chatsworth Ca

2012 9c1 ported LSA kooks 1 7/8 long tubes rotofab cai 575rwhp 570 tq. best repeatable 1/4 mile 11.32
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IDLife Caprice
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Re: 3.45 Differential install

Post by IDLife Caprice » Tue Jul 21, 2015 3:10 pm

I really appreciate the OP sharing the information about this upgrade, it is definitely one I plan to make in the short future.

Many of you will recall I have completely rebuilt my L77 and its now a LS2/3 hybrid of sorts. Since completing the build last month, I have logged almost 5000 miles on the engine... driving from ATL/HOU/ATL/VIR/ATL and now in Columbia, SC.

I would love to go the 3.45 route but I am loving the 20+ mpg and quiet I get at 80+ mph. I also plan to do a twin-turbo build, so I think the 3.27 route would be best suited for my car. With that being said, is there anyone here with the 3.27 gear installed who can share their real-world experience? I am interested in what RPMs you see at 80-85mph and if your MPG took a nose dive or actually improved. On my last trip, I had to drive at a slower rate due to traffic and my MPG dropped because I am out of the power band of my cam at anything below 2000 rpm... so for my application, I am thinking the 3.27 will put me in a torque sweet spot for freeway cruising.

jackleg
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Re: 3.45 Differential install

Post by jackleg » Wed Nov 09, 2016 11:29 am

Hendo wrote:I used a gearing calculator http://www.grimmjeeper.com/gears.html" onclick="window.open(this.href);return false; and ran some numbers. Stock with 235/50 18s @ 6000 RPMs with 2.92s max speed(theoretically) in each gear is 41mph in 1st, 71mph in 2nd, 109mph in 3rd, 145mph in 4th, 196mph in 5th and 249mph in 6th. With the 3.45s @ 6000 RPMs 35mph in 1st, 60mph in 2nd, 92mph in 3rd, 123mph in 4th,166mph in 5th and 211mph in 6th. This is my hypothesis on the effects of 3.45s with stock hp or mild bolt ons and/or a performance tune. A dramatic decrease in the 0-60 time, the 1/8th mile and at least a 166mph top speed in 5th. It does look like the 1/4 mile may be slightly hampered with 3.45s considering that with 2.92s 109mph comes at the top of 3rd gear, with 3.45s the transmission would have to shift into 4th after 92mph and 4th tops at 123mph. I worry that the engine would fall out of the power band (after the 3-4 shift the rpms would drop to 4501@ 92mph and would be @ 5332rpms if it trapped 109mph ) and the 1/4 mile time might not be much better than with 2.92s. I would like love to see what the effects would be in real world testing. I believe 100% that the 3.45s would be more lively on the street and at the sort of speeds people drive on the street. Might not be the best choice for 1/4 mile drag racing though. I would also be interested in seeing the effects on 70 mph highway cruising mpg between stock @ 1689rpms with AFM and with 3.45s @ 1995rpms and AFM turned off or deleted. I am guessing that 24mpg (EPA rating) for example could drop to 20mpg. Doesn't sound so bad but, that would mean spending 16.66% more on fuel to travel on long trips. Over 300,000 miles getting 24mpg compared to 20mpg @ $4 a gallon would cost you $10,000 more...something to think about although obviously not a huge priority to muscle car aficionados. I am not trying to be negative at all, I think what you did is AWESOME. I just wanted to share some things that started rattling around in my head when I saw this and considered doing it myself.
I'm curious about this discussion- (I have a Camaro 3.45 coming for my DD)
Has anyone recorded before and after 1/4 mile times?
I'm not an expert and have very little 1/4 mile experience. It just seems like being able to get the car up to speed earlier on the track would result in lower elapsed times even if the final top speed was ~the same. The car would be going faster on more of the track.
I can see if it was a 3 speed trans then you would want to be at max RPM in 3rd across the finish, but if there are more gears to go why not use them- as long as the tires can hold traction?
2011 9C1 6.0
RCR "Little Lunati" 219/223 .625/.625 112+0
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9C1fanatic
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Re: 3.45 Differential install

Post by 9C1fanatic » Wed Nov 09, 2016 6:54 pm

I was going to say...to keep it over 2000 RPM with the factory 2.92s you would have to bee hauling ass everywhere you went. I don't think I get over 2000 in 6th till 80-85. I assume you are running an LS2 or LS3 cam shaft? I was curious because I have a 3000 mile GM LS3 cam shaft that I was thinking about putting in mine when I did the DOD delete but was still on the fence for fuel mileage since the LS3 likely less torque than the L77 at the RPM range the Caprice is meant to cruise at with the 2.92s. I got burned before when putting a Y body spec LT1 into my 1994 Caprice with stock 3.08 gears and despite the 300 hp rating the car was not much if at all faster than stock in the 1/4 mile and fuel mileage took a noticeable hit. Despite the iron head LT1s lower peak rating, it definitely made more power in the lower rpms. I don't mind losing to fuel economy for a faster car but in my last experience, I didn't get that either. On the other hand, I think a 1990s Caprice weighed much more than an F body or Y body where as the new Caprice is probably not that much heavier than a 5 gen Camaro with an LS3.
Garner Ames



1975 Pontiac Grand Am L77 - 14.82 @ 92.89
1991 Chevrolet C1500 L31 Vortec/5 Speed
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CrashTestDummy
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Re: 3.45 Differential install

Post by CrashTestDummy » Thu Nov 10, 2016 5:11 pm

I believe 2000 RPM is right at about 78 MPH, so yeah, you're moving along.

I'd think the 3.27 would be a noticeable update, and not kill MPGs that much. Unless you're wanting a drag car, they'd be about the best compromise between performance and street/highway manners. That's what I'm looking for, since I still have to drive our Caprice on the highway often.
Gene Beaird,
Pearland, Texas
2012 Caprice 9C1
1992 B4C 1LE Camaro
2010 Tahoe PPV (her car)
1995 DGGM Impala SS
1996 BBB Impala SS (11-second DD)
1985 Firebird - 310 LS1 C Prepared autocross car.
And some others
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