RL90LS400

Hey everyone,
Today I am officially the owner of a 1990 LS400. I'm glad I could find a group like this to help with starting some upgrades and general maintenance. The previous owner just replaced the rear differential about a week ago, however now you can hear a faint humming noise coming from the back of the car at about 55 mph when you're just giving the car a little gas. If anyone knows what this could be, I would love to hear an answer. I think I'll be taking it to the dealership anyways though since the starter is also dying. Also, does anyone know where I could find more information on upgrading the sound system of the car? It doesn't have the deluxe nakamichi(that's my best spelling) so I'd like to upgrade the front speakers and then probably the beast on the back deck as well as the headunit. If anyone has any recommendations or instructions on how to upgrade any of this, I would be very grateful for any info. Also, one last question, on the right back of the car, it says 'plaza' in black cursive writing. Does this have any significance? Once again, thanks and I'm looking forward to hooking this car up.

-Rob

chliansh

Sorry,
Humm\Howl that changes tone with speed (under power or coasting) does not sound good.

Diffs are not for the average grease monkey. If they dont set it up 100% perfect you WILL have problems.

RL90LS400

Well, it doesnt change tone at all, if you slow down or speed up, it's gone. Is that any better? Also, if it is the diff, that would be great, because it's warranteed for another year. If it is broken, would it be possible to put in a LSD? If anyone knows, I would be very thankful for an answer. Thanks chliansh for the quick response.

-Rob

chliansh

I am really not an expert by any means but my ls 400 and all the others I have drove have no noticeable driveline noise at all.

My understanding (jump in anyone) is that this type of noise is caused by missaligned parts "backlash?" or how the gears touch or match up.

As far as a LSD, does yours have traction control? If not I think the LS 400 shares might some parts with the Supra, maybe even a LSD.

If you floor yours from a stand still can you spin the tires? My 94
starts out too soft to even come close unless your on loose gravel.

RL90LS400

Mine does not have traction control and yes, I can spin the tires from a stand still, especially with any snow on the ground. I have a video of my friend doing some donuts in it if someone could host it for me. Can anyone confirm anything about the LSD? I'm really thinking about having one put in if it is possible because it would definitely help with the traction issues. Thanks for the help.

-Rob

Pianoman72

I don't know if this helps but when the diff was going out on my '72 Cutlass the diff made a whining noise when I LET OFF the gas, but NOT while accelerating. Sold it because of that so I don't know what happened.

RL90LS400

That was exactly what this did when I test drove it, but then the previous owner had the diff replaced. I literally bought it like 2 days after he had that fixed, did it 2 weeks ago. So I'm thinking maybe the rebuilt one they put in has a slight defect, or maybe a bearing or something was incorrectly installed. Any ideas or knowledge on a LSD would be great. Thanks for all the help.

-Rob

rybikowsky

mine was making a little noise.I drained the rear and put in mobil syn.gear lube,no more noise.

Lvangundy

I wanna see that snow donut video. ;-)

retrodrive

Once you remove the rear seat you can sometimes clearly make out the whining noise of the gas pump. That might be your problem. Talk to a mechanic about it and he should tall you whats up.

LexJunkie

rybikowsky

What weight synth. oil did you use in your differential???

Darek

rybikowsky

Mobile only has one type it is a multi grade weight.I have used it for years in my bikes cars and even my gravely.