91 Q Transmission, I searched...

[cyyoung2000]

I searched and didn't find this exact problem. But heres whats up, right when I hit 45 mph, the entire car shakes for about a second like an earthquake, then stops and everything is fine. It almost feels like its slipping or something, but i dont know much about transmissions. This only happens about once or twice a week, but other than that everything is perfect. What could this be and is it something i should be concerned about? Thanks in advance...

[Q45tech]

i dont know much about transmissions

A year at transmission school can solve that problem, however not usually worth the time and expense unless you make your living at it.

Take it to a certified Infiniti technican for a diagnosis with Consult. The real Consult has special software to diagnose transmission.

Could be rear transmission mount and or driveshaft needs replacing,when were engine motor mounts last replaced?

The only down side to a transmission repair shop is every problem they solve requires a new transmission.

[maxnix]

What is the transmission maintenance hsitory? Third motor mount replacement whas when?

Chain guides?

[cyyoung2000]

I have no idea about the transmissions history (haven't had the car too long and not in history report) I don't think the mount has been replaced either. but guides were done.

[maxnix]

OK, then you need to start with an ATF mechanical fluid exchange, pan drop and wipe clean, magnetic plug inspection, and interior filter and Oring replacement, along with pan gasket and one time use bolts. You probably should add an auxiliary ATF cooler too like a B&M70268 or 70264 from http://www.summitracing.com

Get the parts from http://www.infinitipartsusa.com

Call the BG shop to see if they will perform the service you require.

http://www.bgfindashop.com

Might also try a search in body in current and archived for the word flush. Read all of Q45tech's posts.
Modified by maxnix at 9:28 PM 7/16/2007

[cyyoung2000]

How much should I expect to pay for the services, excluding the ATF cooler. Thanks I appreciate the help...

[texasoil]

THe substantial shuddering you describe all too briefly may be torque convertor lock-up shudder, May be other things too. First step is a good look-see underneath to ensure no loose or broken mounts, drive shaft flex joints,engine mounts,etc, THat it happens only occasionally argues for a sticky valve in the lock-up clutch (which can usually be cleared up with a good flush (Use BG products) followed by adding a pint of LUBEGARD RED (which is the ideal lubricant to resolve a 'lock-up' shudder caused by poor friction chatacteristics of that clutch lining.)

I am not an expert on the transmission valve body details, but I do know varnish in the critical clearances will mess up lots of things, and it only takes a single thread of fiber to make a valve stick

[maxnix]

How much should I expect to pay for the services, excluding the ATF cooler.

Labor rates vary, and whether you supply your own M1 ATF (ideally with ~6 oz. of Lube Guard Red - not black)or use theirs synthetic, or use a dose of BG Quick Clean immediately before flushing system while still warm.

Altogether, probably ~$250.

In LV, you really need the auxiliary ATF cooler, and it is cheap for what it does. Q45 out of LA were known for fried transmissions for making the slightly uphill LA to LV run.

Check under my board name in the gallery for some pictures for variou installations.

[96Qowner]

right when I hit 45 mph, the entire car shakes for about a second like an earthquake, then stops and everything is fine.

Let's clarify. Does this happen only under acceleration? If so, it's almost certainly your transmission (rear engine) mount. It will cause vibration at 2250 rpm in all gears. If it's the transmission mount, it will happen as you accelerate through 45 mph and 70 mph. (2250 rpm). Common issue on older Qs. If that's what it is, be sure to also replace the exhaust hangers.

If it's simply erratic when you're just cruising at 45, it's something else.

[wlong]

I had the exact same problem a few years ago in a Nissan Maxima. Texasoil's response is exactly what I did and it pretty much fixed the problem. In my case, the shudder only occured when the converter locked up at the lowest lockup speed -- around 45 mph.

[cyyoung2000]

Yes it only happens when i accelerate straight TO 45mph, not when I'm coasting. But I'll replace the mount and the hangers and we'll see what it does...

[maxnix]

If you have a vibration in 3 at 47 - 49 mph and 67 - 69 mph in D, and tires are OEM specified 26" diameter, then the 3rd motor (transmission) mount is suspect.

But if you haven't exchanged the ATF fluid and added a cooler, you are probably overdue for that also.