New Caprice - Discussion forums

bstoner wrote: ↑Sun Aug 01, 2021 11:23 pm Here is where I had to grind the cover to get clearance to fit inside the mount.

I have the same cover. I also had to grind the left adjuster bolt down to the nut as it was hitting the cradle. Are you sure that's all you need to grind off of the case? I had to go a little deeper to make sure it wasn't touching the cradle. I didn't want any clunking or rattling.

My left adjuster shaft is close but doesn't touch. Interesting how much difference there is between cars. The only thing I don't like is the TrueTrac makes a slight clunk on/off throttle. You can hear it if you have the radio and A/C off. Apparently that is normal. I was worried I did a bad install. I pulled the carrier and took it over to a 4wd shop for them to double-check my work. They said it looked good; and clunk was normal. Relief... I am mechanical but not a rear end guy. Didn't want to spend over a grand on a rear end to just destroy it due to installation error.
https://www.eaton.com/us/en-us/products ... -faqs.html

Q: When I step on and off the gas pedal, I hear the unit make a “clunking” noise. Why?

A: This happens because Eaton Detroit Lockers have “backlash” or “slack” between the drive and driven teeth and you will hear this in everyday use going through corners and when transitioning from drive to coast. Also, with the vehicle on the ground and the transmission in neutral, several degrees of lash in the driveshaft is normal. Here is a formula to calculate the degrees of rotation of the driveshaft: (differential internal lash X ring and pinion ratio) + ring and pinion backlash + driveline slop such as U-joints wear.

To all the guys that have installed these, what's the opinion between 3.27 vs 3.45? I see a few 3.27 LSDs in my area for $400-$500 but no 3.45s I was wondering if it worth waiting for a 3.45?

This will be subjective for each person. I haven't had the chance to try a car with a 3.27. I am NA and wasn't worried about the miles per gallon. I don't have any wheel spin with the 3.45's. I am running a 275 wide tire, 1LE lower control arms and toe links. I tried to firm up the IRS with those components. Seemed to have worked for me.

Maurice

I have a 3.27 with no other significant mods and factory wheels. I have not adjusted anything to compensate. Speedo is off by 11.9%. It does not seem to me that there are any obvious problems without reprogramming for the new ratio.
The car definitely feels like it has more grunt. I too was concerned about gas mileage and opted for the 3.27 for that reason. I think I paid around 500 at a local bone yard. So far I haven't done any significant trips (all city-ish). The indication from the DIC says I'm doing okay with gas mileage but I'm sure its calculations are off b/c I haven't re-programmed.
Many on here swear by the 3.45. I'm glad I've got the 3.27 and not sure how I'd feel with the 3.45.
You might consider changing the ring and pinion on a Caprice Diff to 3.45 and save yourself a ton of cash. Full disclosure: I have a 50-some thousand mile 2.92 for sale for a hundred bucks .
My understanding is that there are three diff's that will fit our cars. A "good" camaro one that came with the V8's, a crappy Camaro one that came with some V6's and ours which is a tweener in terms of diameter of the ring and general durability.
Good luck.

I have not driven a Caprice with 3.27 vs 3.45 so I cannot give a 1 to 1 comparison. I have 3.45 gears now. In my opinion 3.45 is definitely not too much gear for these cars. It's a lot of weight to get up moving. In fact my wife didn't even notice the difference. LOL. She is not a car person. 3.27 is stock for the auto Chevy SS. I think either one you will be happy with and make a noticeable difference. The 3.27 is about half the price of the 3.45 and are much more common. For a budget install the 3.27 is easy to find, affordable, and the way to go. If you want more 0-60 performance then I would recommend the 3.45 and pay the difference. You will probably be waiting a long time or have to pay to ship one to you. For me I am going for an ultimate build. So I went 3.45 with a Truetrac, milled JRE caps, diff cover, poly bushings, new seals, and bearings. I wanted to make it bullet proof to handle high HP. I would also budget for programming the gear ratio in the ECM as well. I have HP Tuners and adjusted it to get the speedo and shift points back on track.

Had anyone tried a 3.91 rear gear in a caprice? I wonder how bad it would be on the highway?

JUNKYARD_JACK wrote: ↑Thu Dec 09, 2021 11:30 am Had anyone tried a 3.91 rear gear in a caprice? I wonder how bad it would be on the highway?

alot of unnecessary wear and tear on parts

JUNKYARD_JACK wrote: ↑Thu Dec 09, 2021 11:30 am Had anyone tried a 3.91 rear gear in a caprice? I wonder how bad it would be on the highway?

RPMs are pretty damn low on the highway with 3.91s. Most people probably wouldn't even notice. I had 3.45s before and there's barely any difference in terms of cruising RPMs. They're great for an NA car with a good tire, but if your car doesn't hook up at all, then it's probably a waste of money. Get some drag radials first.

JUNKYARD_JACK wrote: ↑Thu Dec 09, 2021 11:30 am Had anyone tried a 3.91 rear gear in a caprice? I wonder how bad it would be on the highway?

I guess I would call it unnecessary (opinion!). Since our first gear is 4.0267:1, we might not need that tall of a rear axle. To get some perspective, consider that a 3.73 or 4.11 was really good with old camaro's. Muncie 4 speeds (M21, M22 - called close ratio) had 2.20:1 1st gears. M20 had 2.56:1 first gear. They might have had shorter tires than we have in the Caprice but we still have an overwhelmingly better 1st gear with a 3.27 or 3.45 rear end (with a 4.0267 1st gear) in a Caprice than a 4.11 (with a 2.20:1 1st gear) in a '68 Camaro.

One of the things that allows us to get away with a lot of rear end is that we have 2 overdrives where we had 1:1 4th gear in our old Muncies - (I dreamed of getting a Doug Nash 5 speed back then). Our 5th gear is .8521: 1 and our 6th gear is 0.6667: 1.

I say save some overdrive for the highway and stick with a 3.27 or 3.45. ....but if stop light to stop light or quarter mile dragging is your bag, consider the 3.91.