Replace Diff - what else to do while in there?
Thread Starter
Race Director
Joined: Jun 2013
Posts: 12,412
Likes: 1,750
From: DFW TX
Replace Diff - what else to do while in there?
Planning for a session underneath my car
Recent to me C5Z has horrific diff whine. As in, it sounds like straight-cut gears. Super loud. Whine in all gears, all speeds, on throttle only. No noise off-throttle/coasting/engine braking. I tried synth Valvoline, Redline, and finally filled it with Redline "Shockproof" Heavy Oil as a cheap things to try. Zero effect. Diff is an RPM Level 2 with C6Z output shaft and 4.10 gears, very low miles, under 5k. I suspect it was set up wrong and/or not broken in properly.
- Plan to drop the whole driveline less engine.
- Will likely have RPM rebuild diff
- Will rebuild the Spec super twin clutch at the same time to be less grabby.
- what else should I check while everything is out? TT? couplers, bearings, etc etc?? TT is supposed to be new C5Z with 5k on it as well.
- Trans is RPM Level 5 with under 5k as well and seems perfect
thanks in advance
Recent to me C5Z has horrific diff whine. As in, it sounds like straight-cut gears. Super loud. Whine in all gears, all speeds, on throttle only. No noise off-throttle/coasting/engine braking. I tried synth Valvoline, Redline, and finally filled it with Redline "Shockproof" Heavy Oil as a cheap things to try. Zero effect. Diff is an RPM Level 2 with C6Z output shaft and 4.10 gears, very low miles, under 5k. I suspect it was set up wrong and/or not broken in properly.
- Plan to drop the whole driveline less engine.
- Will likely have RPM rebuild diff
- Will rebuild the Spec super twin clutch at the same time to be less grabby.
- what else should I check while everything is out? TT? couplers, bearings, etc etc?? TT is supposed to be new C5Z with 5k on it as well.
- Trans is RPM Level 5 with under 5k as well and seems perfect
thanks in advance
Racer
Joined: Jul 2018
Posts: 335
Likes: 139
- Rear main seal
- Pilot bearing
- Inspect and consider replacing rear suspension components (control arm bushings, ball joints, hub bearings, shocks, sway bar, sway bar endlinks)
- Brakes / brake lines
- Fuel filter
- Check for leaks between transmission and extension housing
- Install remote bleeder (if not already have one)
- Pilot bearing
- Inspect and consider replacing rear suspension components (control arm bushings, ball joints, hub bearings, shocks, sway bar, sway bar endlinks)
- Brakes / brake lines
- Fuel filter
- Check for leaks between transmission and extension housing
- Install remote bleeder (if not already have one)
Last edited by FR-CYA; Jan 15, 2019 at 12:12 PM.
Thread Starter
Race Director
Joined: Jun 2013
Posts: 12,412
Likes: 1,750
From: DFW TX
Makes sense
Will check and replace those items as needed.
Car has 32k and most suspension components have under 5k. Derlin bushings, shocks/sways, endlinks etc all those are good.
Slave already has a remote bleeder.
Fuel filter is a good idea
Will check and replace those items as needed.
Car has 32k and most suspension components have under 5k. Derlin bushings, shocks/sways, endlinks etc all those are good.
Slave already has a remote bleeder.
Fuel filter is a good idea
Drifting
Joined: Jul 2012
Posts: 1,325
Likes: 239
From: Missi'ppi... no mo' MO for me!!
I'd suggest you very carefully inspect the TT couplers. You don't have much mileage on the car but the couplers are old. I thought I could reinstall mine because they looked fantastic; like new... but I inadvertently twisted them somehow (I can't remember what I was doing; I think I was force-fitting them into a box) and the rubber crumbled under the torque/pressure. Old age memory loss... I can't remember how I did it; all I can remember is the image in my mind's eye of the rubber crumbling in my fingers--though I do remember it took a lot of "work" to destroy the coupler.
Thread Starter
Race Director
Joined: Jun 2013
Posts: 12,412
Likes: 1,750
From: DFW TX
I'd suggest you very carefully inspect the TT couplers. You don't have much mileage on the car but the couplers are old. I thought I could reinstall mine because they looked fantastic; like new... but I inadvertently twisted them somehow (I can't remember what I was doing; I think I was force-fitting them into a box) and the rubber crumbled under the torque/pressure. Old age memory loss... I can't remember how I did it; all I can remember is the image in my mind's eye of the rubber crumbling in my fingers--though I do remember it took a lot of "work" to destroy the coupler.
I've been putting it off but I need to determine what is 'best practice' for TT couplers: oe or some form of aftermarket. I believe people were using Derlin or solid aluminum couplers but there were drawbacks.
I want to do it once, right, and not worry about it again. Car is about 550whp, runs 200TW tires and I don't 'launch' it; I drive gently. So no extreme solution is needed.
Thread Starter
Race Director
Joined: Jun 2013
Posts: 12,412
Likes: 1,750
From: DFW TX
From reading old threads, Driveshaft Shop seems to be the go-to vendor
http://www.driveshaftshop.com/ As I get closer I'll give them a ring to discuss options.
I'll call RPM as well since it's their diff; they have been great on the phone.
I bought a full FSM to ensure I do it right the first time.
http://www.driveshaftshop.com/ As I get closer I'll give them a ring to discuss options.
I'll call RPM as well since it's their diff; they have been great on the phone.
I bought a full FSM to ensure I do it right the first time.
Acct Suspended APR 2026 by request
Joined: Dec 2010
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2020 Corvette of the Year Finalist (performance mods)
C5 of Year Winner (performance mods) 2019
dss has a 3.5" driveshaft that eliminates the couplers, that would be the strongest option and probably the only con is increased noise at idle... it probably weighs a little more than the stock setup with couplers but I don't think you would really notice a difference when driving the car... I have their 3" shaft with poly couplers in my car, I went with the 3" because I already had the couplers on my stock driveshaft but if the drivetrain ever has to come out again I might consider replacing it with the 3.5" so I don't have to mess with couplers anymore
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