Rear Differential Whine in '91 Q

[StillFastQ]

Hi,At the end of my rope, looking for salvation. '91 Q45t, runs great, but there is a LOUD whining that starts as soon as I start rolling in gear and gets louder the faster I go. One Infiniti mechanic said it's the driveline. Another I-mechanic says it's the rear diff. They won't work on it, will only replace it. replacement cost, $2,800. What does the online mechanic say?

A) Is this common in a Q with 150k miles?B) Could it be something else?C) If not, is there a fix other than complete replacement?D) If no to C, can someone point me to a good pick-a-part in Southern California?E) If yes to C, can someone recommend a reliable independent mechanic in Orange County, CA?

Thanks a lot, I've been reading this forum a lot, and this is the first time I've had to post.

Cheers, G

[Q451990]

Hi,At the end of my rope, looking for salvation. '91 Q45t, runs great, but there is a LOUD whining that starts as soon as I start rolling in gear and gets louder the faster I go. One Infiniti mechanic said it's the driveline. Another I-mechanic says it's the rear diff. They won't work on it, will only replace it. replacement cost, $2,800. What does the online mechanic say?

A) Is this common in a Q with 150k miles?

Depends on the maintenence history. If the fluid in there came from Japan, I'm not surprised. With even marginal fluid changes, you should get around 200K.

B) Could it be something else?

Possibly the driveshaft... typically you'll find play in the center carrier, but that usually shows up as a balance issue. Maybe a rear wheel bearing? A good tech with a mechanic's stethescope is the best way to pinpoint this type of thing.

C) If not, is there a fix other than complete replacement?

Cheaper and easier to replace with a used unit - preferably low mileage from a 1996.

D) If no to C, can someone point me to a good pick-a-part in Southern California?

Check out www.carpart.com

E) If yes to C, can someone recommend a reliable independent mechanic in Orange County, CA?

Jerry Tucker has a lot of Q experience. I'd have him give you a third opinion on the problem too. It may be a bit out of the way, but it would be really worth your time to go! Many members have had very good experiences with him. If you haven't gotten your chain guides replaced, he can do that too. This guy has a very good reputation.

Welcome to NICO!

Heath

[DAEDALUS]

San Diego is a bit far. There is a salvage yard in Wilmington I go to and they have Qs back there. Not the cheapest place, and I go there as a last resort, but I'm sure it'll be cheaper than $2800 including independent installation. Their number is 310-834-7583. Have you tried replacing the gear oil? If you do a swap, consider going to a 4.08 ratio for better acceleration. Lowers mileage a bit though.

[AZhitman]

I can get you a 4.08 rearend with relatively low miles for a great price locally. Shipping might be $50-$100, but it's not a HUGE DIY job. If you're reasonably competent with tools, I'd say go for it.

[StillFastQ]

I'm looking at the number of posts you guys have made, and the detail in your responses, and I know I came to the right place...From your consensus it looks like the rear end, so I need to look at the options that fall out of that.The I-guy in Mission Viejo said there's no reason to change the gear oil out because once the gears have worn that much, it's hosed anyway and will just start whining again. Agree or disagree?BTW, my dad suggested just throwing sawdust in there to shut it up... any merit to that at all?

I checked carpart.com, and forgive my ignorance but what is the difference between a differential and a carrier? There's a ton of carriers (avg. price $500) on that site but no differentials.

I will call the place in Wilmington and check my options there, then get back to you AZHitman. Are there any other repercussions from switching to the 4.08 rear end?

You guys are gods, I am not worthy.

[AZhitman]

Agree with the I-guy, disagree with Dad. (sorry dad)

Do a search on "4.08", as a few Q owners have made that switch. It's really more of a performance mod, netting you approximately a 15% overall gearing reduction and increasing acceleration (at lower speeds). Maybe a slight loss of fuel economy (what's economy?) but other than that it's a pretty benign mod.

Alternatively, you can swap a rearend from a wrecked 90-96 Q and keep the same ratio. Prices vary, so check around.

[Q451990]

I still wouldn't rule out Jerry for the install... and if you haven't had your guides replaced, I wouldn't spend another dime on the car for other repairs, wear ear plugs until the differential smokes - you're living on borrowed time with the guides as it is.

Heath

[StillFastQ]

Q451990, I am going to give Jerry a call on the guides at the least.AZHitman, I'm going to look at wrecked Q's first, then get back about the 4.08 switch. Thanks a bunch for all input.

Did anyone know the diff between a diff and a carrier?

Thanks, G

[AZhitman]

I think it's two terms for the same assembly.

[90Q45blue]

I think so too but the best way to check would be to call one of the salvage places and ask.

Nick

[maxnix]

Did anyone know the diff between a diff and a carrier?

Could a "carrier" be the whole rear subframe with the differential attached?

[90Q45blue]

Hmmm....that could explain the reason they are more expensive than simply the differential on car-part.com.

Nick

P.S. I'd call a salvage yard to double-check.

[AZhitman]

I just called AutoGator (So Cal Nissan graveyard). They have an R200 rearend with the 4.08 gears for $350, no core required. It's out of a wrecked 300ZX with 93K miles.

That's a smoking deal, I may grab it if you don't.

[DAEDALUS]

Actually they're in northern Cal. I wish they were down here though. I'd be a very frequent customer.

[AZhitman]

He said $30 to ship to Phoenix.... WOW.

I wouldn't let the distance stop you, esp at those prices.

[Highway Q45]

Autogator is about 2 miles from my house. Great place to wander around on a cool morning. These guys are honest and very savvy about Nissan/Infiniti so your Q dollars don't go as far as finding a Gen1 Q in some generic salvage yard and getting parts for low $. They wanted $65/each for sunvisors, and they were worn out just like mine at the spring nut. Steve

[Q45Viper]

Oh, great! The sunvisors wear out? When does it stop?! Where does it end?! What kind of synthetic fluid do I have to put in THESE things to extend their life? .......A little humor for those of us WELL on the road to $$$$ rebuilds! I read that about the sunvisors and said "OH, Sheet" out loud! I don't wanna read nuttin' about ANYTHING else that needs to be fixed, I just came back in out of the rain after checking my spring nuts or whatever they are on the sunvisors.... well, at least I could'nt find any guides or anything on them to replace, there's no hoses and nothing to clean there and best of all NO RELAYS!

[Q45tech]

The differentials are different [whether there is a single ABS sensor on the input [standard Q] or two ABS sensors one on each output shaft [Traction option or Active option].

We change the entire differential frequently on high mileage Q......net about $1,000 with a decent junkyard take out.............even mine got replaced around 220k when the new rear subframe was installed 2 years and 31k ago...........found a 56k unit from a 94Q for $300 delivered [professional discount price].........my viscous was worn out and the input bearing was making noise.

Junk yards are very savvy and usually charge 35-50% of new retail unless you are a frequent buyer in the trade [a service shop]. We probably do $30,000 per year with just 2 yards so they treat us right........but that is small potatoes compared to the $660,000 we spend with Infiniti and Lexus combined.

[don5154]

I lost the rear end on a 90 q with 125,000 miles a few years ago. found a used one in San Fernando Ca for $200 and installed it in about 4 hrs. I think the salvage yard had Nissan in it name. It was located on San Fernando Rd. Good luck.

[Q45tech]

That's a good price we pay $300-$400 depending on what is available and the whole job runs $1000.........but remove the cover and look and reseal before installtion to give the 12/12 warranty............compared to a $3,000 new dealer replacement.

Mileage on used is very important as the viscous tends to get worn and soft engaging after 100-150k........doesn't take much spinning [stuck in snow or heaven forbid the old fashioned on the car balancing to warp the viscous plates].

Changing the diff fluid every 30,000 miles or 2 years seems to allow them to function quietly for over 200,000 miles.

Bad wobbley drive shafts wear the front bearings fast and are usually the cause of the early whine if the fluid has been well maintained.

[s13sr20chris]

Q451990, Did anyone know the diff between a diff and a carrier?

Thanks, G

carrier is another word for the differential case, not the housing though. the diff case or carrier is the thing the ring gear bolts up to. i have seen it used as a term for a whole rear end.