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3.90 Richmond set up

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Old 02-03-2021 | 08:42 AM
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Default 3.90 Richmond set up

New to the site. I'm just looking for a little advice. My 99 z diff played out back in May. Factory 3:23 w traction control. Not a bad set up, how ever I found a used axle to put under. Complete axle with 3:90 Richmond gears. The guy selling 390 let me drive his 2000 bird which has the 390 Richmond under it. I guess before he pulls the axle out of his car to sell me, he wanted me to hear the winding it makes. As he explain he bought the car from a mechanic which installed the gear set in the axle. So his defense is the mechanic set it correctly. The mechanic also said that Richmond gears are noisy and completely normall for it to make so much noise. While driving the car I notice the noise started out soft wind and got louder the faster I went. Pretty loud in my opinion. Idk if I buy this if I could stand listening to this for my z28 is my everyday driver. And yes I know a 390 is not a good choice for everyday driver as it will suck the gas, not concerned bout the gas. I just want it back on the road. If I knew how to set up backlash and etc I would buy new gear set and go with 373 gears and do it myself. Unfortunately I dont know how. Also the guy with the 390 offered to help install the diff under my car. So help with removal of my old axle and installation of new one everything for 500. Bucks. Just afraid of the noise it making. Is this normall for Richmond gears to be so loud? And what would u do? Note I also found a complete axle about 2 hours away. Been sitting about 2 years after car broke down. 2:73 with traction control. He said it was good when he parked the car. 100 bucks for his. Not so sure about it because it's been sitting idle for so long
Old 02-03-2021 | 08:39 PM
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Yes, Richmonds are known to be 'noisy'.
Is the 3.90 complete rear from a traction control car ?
Old 02-04-2021 | 08:04 AM
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Not from a traction control car. The car the 390 is in now has the traction control button on dash just like my z28 does. I ask him about the axle not having traction control and he said it was fine that it doesn't matter if the axle has it.
Old 02-04-2021 | 08:08 AM
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So the 390 is from another car I'm guessing, that doesn't have traction control option. Or the traction control doesn't work in his car. He bought the transam like it sits with the 390 under it.
Old 02-04-2021 | 08:22 AM
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A 3 channel ABS only-non traction control rear end put into a 4 channel ABS/TC car will cause the dash's ABS light to come on and the light cannot be tuned-out because it's part of the safety protocols. The brakes will act like brakes of the past pre-ABS.
And any rear gear change will necessitate a computer re-program to correct the speedometer and auto transmission shift points.
Others will/should post in to verify this.
Old 02-04-2021 | 08:58 AM
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A 3 channel ABS only rear end has one sensor on top of the rear end to sense the reluctor ring mounted on the ring gear carrier. A 4 channel rear end has 2 sensors, one mounted in the backing plate/dust cover in each end of the rear end assembly to sense the reluctor ring mounted on each axle shaft.
Old 02-05-2021 | 12:05 PM
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Couldn't the axles on his 3-ch 3.90 rear be pulled and the reluctor rings (and sensors / harness) from his original 4-ch rear be moved over to the 3.90 rear (or just swap axles)? Leave the sensor on the 3.90 pig un-connected, the reluctor on the ring gear just goes along for the ride.

FWIW, the Richmond 3.90 gears I put in my Cutlass axle when I rebuilt it years ago were noisy too, even though I got the gear mesh dead-nuts on. After a few thousand miles, its gotten quieter, but not silky quiet like OEM gears.
Old 02-05-2021 | 01:45 PM
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Originally Posted by JohnnyBs98WS6Rag
Couldn't the axles on his 3-ch 3.90 rear be pulled and the reluctor rings (and sensors / harness) from his original 4-ch rear be moved over to the 3.90 rear (or just swap axles)? Leave the sensor on the 3.90 pig un-connected, the reluctor on the ring gear just goes along for the ride..
YES, TRUE. I didn't bring that up because it seemed he was talking about a quick easy swap. Axles w/reluctors, backing plates, and backing plates dust sheilds would have to be interchanged. Both rears would have to be torn apart (to a point) to get those. AND/IF that 3.90 rear,which already has been modified to 3.90s', the possibility exists that in the rework of that rear end, 'axle saver bearings' were used, he'd run into a potential brick wall trying to get the c-clips out.
Old 02-06-2021 | 07:39 PM
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Sounds like it might be more trouble than I want. I know another guy that has a 2:73 with traction control. Come out of same car as mine. Only difference is my factory gears was 3:23. Would I have to switch harness since both cars have trac control???
Old 02-06-2021 | 09:01 PM
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Since yours is a 99 and if the 2.73 rear is from a 98-02, would be a direct swap with no harness change. But going from 3.23 to 2.73 will feel like you've lost 15% of your power. And you'd need to correct the computer to correct the speedometer and the autos' shift points.
Old 02-07-2021 | 10:45 AM
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If I dont correct the shift points, will that make the transmission go out?
Old 02-07-2021 | 12:25 PM
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As far as the speedometer, since the cars' computer is setup for 3.23s', when the 2.73 rear end is put in and no corrections are made, when the speedometer is indicating 51mph you'd actually be going 60mph.
I use my Hypertech handheld programmer to change the computer for adjusting the gear ratio change. Even though the Hypertech is capable of some changes I only use it for rear end gear ratio changes and engine coolant temperature for when the fans should come on. All the other adjustable changes built into the Hypertech are worthless.
I've never driven mine after a gear change for an extended drive other than to check rear end function so I can't answer your question about tranny life.



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