Need help with "90 Q

[Q45denver]

I have a few questions I'd like to get answered and would appreciate any response.

-The brakes are OEM but difficult to modulate (grabby and jerky) compared to most new cars. Would a different type of pad (metallic type) help? I'd gladly give up some stopping power for smoother brakes.

-When draining the transmission pan (I have drain plug on pan) would it be safe to run the engine for a few seconds to get some more of the fluid out of the torque convertor.

-The transmission has a rough 1-2 shift (93 TCU). Sort of a sling shot effect under hard acceleration. Can anything be done short of putting the original '90 TCU back in.

-With 150K miles it may be time to replace the driveshaft. Would a good shop be able to tell if it's out of balance?

-After replacing the differential fluid should I add a limited slip moly additive?

:help

[DougQ45]

I can only answer as to the transmission pan drain. With the low pressue (15-30 PSI) in the system, you could let it run for a bit, but I don't see any advantage. Fluid gets picked up through the pump which is in the pan, then distributed to the TC, then into the heat exchanger, then returned to your rear planeary gears. All by virtue of the transmission fluid pump. Maybe if you just drain and refill 2x in a 30 day period???

[Professor_Mike]

The brakes sound like the rotors may be warped, does the steering wheel shake with moderate braking at 60mph? OEM brakes work quite well.Suggest a transmission flush with synthetic to change all the fluid, members report improved shifting after this.Driveshaft vibration usually shows around 30 to 50 mph, it is difficult to find someone to rebuild the Q driveshaft.Using the recommendation in the manual for diff fluid is sufficient, synthetic best.

[greg_atlanta]

OEM brake pads are very good... is that what you're using now? Good idea to resurface the rotors at least once a year. Makes a big difference in feel when the surface isn't warped and/or oxidized (they should be bright silver).

No fix for the '93 TCU issue. I have a '93 TCU in my '92 Q and I find it'll drop into 2nd gear softly if I floor it in 1st gear, hold it until about 6000 rpm, and then let off the gas.... then it just quietly drops into 2nd gear. (Good technique for stoplight to stoplight fun).

I switch back to my original TCU in winter since the '93 TCU tends to make the engine rev too high on startup (I'm not always Mr. Perfect about warming the car up when it's cold outside).

I wouldn't replace the driveshaft unless the vibration is bothering you. It's really just a quality-of-life issue. I spent $1000 replacing my driveshaft and trans mount (175K miles) and it does feel better, but it doesn't feel $1000 better. Not the best bang for the buck, but I did put it off for 3 years.

[Q45denver]

Thanks for info. The brakes pads and rotors are new OEM all around except rear rotors were resurfaced. Also recently installed stainless lines. There is no vibration on braking just hard to modulate therefore I thought maybe different pads might not be so grabby? As for the transmission, I have flushed it recently with Mobile One and added bottle of Lube Guard but it didn't appear to make any difference. Sometimes when its cold it doesn't shift as rough. Still prefer it over second gear start. Its been snowing all week in Denver. No problem with first gear start because there's 30% less power at 5000 feet.I'm not sure if the differential has vibration. Sometimes I feel some at lower rpm's but not sure if its the driveline. Guess I'll just live with it until I can tell for sure it is the driveshaft. I noticed the new Z car uses a carbon fiber one-I assume the G35 coupe does also?

[greg_atlanta]

I noticed the new Z car uses a carbon fiber one-I assume the G35 coupe does also?

I don't think so. The wheelbase is longer so that means the driveshaft is different.

I wonder is the carbon fiber driveshaft in the new Z is an added expense?? Seems Nissan is trying to cut costs wherever possible.

I think the aftermarket Z community is big on carbon fiber shafts, so putting in the new Z is probably just to appeal to former Z owners.... not sure if it really makes a difference. The car's still pretty heavy for a little sports car, so if they were worried about weight, the driveshaft wasn't going to drop 400 lbs. :rolleyes