94-96 Transmission in 90-93 Q

[JohnPa]

I'm getting a low level vibration that I can almost hear and barely feel at 60 mph, and I suspect the transmission. Factory wheels, new tires, new driveshaft, replaced right axel shaft, new left rear wheel bearing, new motor mounts, new transmission mounts, new exhaust system hangers, etc. The brakes have not been replaced and the fuel pump is humming a little, so it is on order from Joe and I will replace it before I do anything drastic.

What are the chances the problem is the brake system?

If it isn't the fuel pump or the brakes, how can I tell if the transmission is the source of the vibration? I can put the car up on railroad ties and run it up to 60 mph, but the suspension is just hanging there and I'm not certain that anything I notice in such a no-load situation is a real problem. By the way, this is the method I used to find out my tires seemed out-of-round, my driveline shimmied, and my right rear axle wobbled.

Comments/suggestions appreciated. The shimmy is very slight, but this car is just too nice to let it go.

Thanks...........John

[JohnPa]

Well, dumb me, I forgot to add that if I need a transmission, can I put in the later unit which seemed to have fewer problems? And, are the later units a good bet used??

John

[Q45denver]

I doubt its the transmission, fuel pump or brakes. Always check the easiest thing first (tire balance). If there's a noise you might try to locate the source. They have some remote mics you can install to hear while driving. How many miles on transmission. Take it out of gear and see if it does it while coasting. Did it start when you installed the driveshaft? Yes latter transmission will work but first gear is higher. Longevity of latter ones is mostly due to addition of filter and first gear start..

[sijoko]

The 94-96 transmissions will work but if you keep the original TCU you might not enjoy the 2nd gear starts.

I believe that the shorter gap between the first 3 gears helps in keeping the trans alive longer.

On a side note, you will have a real nice 2nd gear for those high speed (80mph and up) overtaking manuevers. There will be less rpm drop when the 94-96 trans shifts into 3rd at full throttle, which means better acceleration.

In regards to your vibration issue: Was the driveshaft installed according to the procedure in the service manual? It is specific and should be followed precisely to eliminate driveshaft vibrations.

Also, about lifting the vehicle and putting it in drive: I have heard that if a tire is spun past a certain speed without any load, it could fail. Maybe someone can clarify that.

[Q45tech]

Maximum instanteous peak acceleration always occurs at the torque peak rpm [~~4,000 rpm] and declines thereafter.

Since tcu shifts are controlled by speed and rpm mismatching the tcu and transmission by 5% can cause some variable responses. ......in 1st and 2nd shifts.

[maxnix]

Also, about lifting the vehicle and putting it in drive: I have heard that if a tire is spun past a certain speed without any load, it could fail. Maybe someone can clarify that.

Yeah, you mean the VLSD? I thought that would be similar to spinning the tires in snow, which also kills it.

[JohnPa]

Maximum instanteous peak acceleration always occurs at the torque peak rpm [~~4,000 rpm] and declines thereafter.

Since tcu shifts are controlled by speed and rpm mismatching the tcu and transmission by 5% can cause some variable responses. ......in 1st and 2nd shifts.

First, if I put the later transmission in my 90 Q, and use the later TCU, should I use the original ECU or the later ECU? In either case I want to have the NICO modified version.

Second, the reason I'm interested is because the shift from 2nd to 3rd in my transmission is slow and drawn out, expecially when it is colder outside. It can take one to three seconds. It was about 55 degrees out today, and I could still notice a slight hesitation. When warmed up, it seems to work fine, even under full throttle. My car has about 96,500 miles on it and the transmission has about 60,000 miles on it.............any ideas or suggestions for a cure?

I am about to take the car off the road again and do the brakes, fuel pump, and anything else it needs, so any help you can give will be greatly appreciated!

Thanks..............John

[DrewQ45]

I have pondered the question extensively. If you don't mind your car being slower off the line then you can go with a 93'-96' transmission.

The Q trans (RE4R03A) has a small metal tag near the tail end. 93-96 will be tagged 51x79, while 90-92 is tagged 51x65.

Better to stick with 51x65 specifically from a 90' or 92' (skipping 91') but there is no way to tell the year once the transmission is removed from the car. There are folks here with 93-96 Qs who have gone retro with their trannys (51x65) for the gearing advantage.

BTW, you should replace your transmission mount and exhaust hangers as they can cause vibes when worn out.

These links should help...

zerothread?id=132639

zerothread?id=129690

Transmission Specs:

90-92

RE4R03A 51x65 transmission 4 speed autoGear Ratio1st 2.784:12nd 1.544:13rd 1.000:14th 0.694:1R200V viscous limited slip differentialFinal Drive Ratio: 3.54:1

93-96

RE4R03A 51x79 transmission4 speed autoGear Ratio1st 2.569:12nd 1.479:13rd 1.000:14th 0.694:1R200V viscous limited slip differentialFinal Drive Ratio: 3.54:1


Modified by DrewQ45 at 9:48 PM 4/8/2006

[elwesso]

drew why do you say you should skip the 91 Q transmission?

[DrewQ45]

drew why do you say you should skip the 91 Q transmission?

Some changes were made for 91' which caused a reliablity issue. I've always heard the 91' was the weakest of the lot but can't give you specifics. I believe Q45Tech will have a more definitive answer to this question as he was the first I saw mention it back on the yahoo boards.

[elwesso]

The actual transmission internals were not changed at all to my knowledge (besides the switch to the different 1st gear in late 93) it all had to do with the cooler that came with the car stock..... which isnt an issue if your using an external.

[JohnPa]

I really, really appreciate all of the input! I'm still trying to find out what my options are Re. fixing my slow 2-3 shift. If I have to replace the transmission, it looks like a rebuilt 90-92, or possibly a used 94-95 unit. (Used units sell here for about $750.)

I also intend to install the J30 3.916:1 ratio differential and thought that would take care of the higher gears in the later trannies. Any comments?

See, I thought that the 90 transmission with the lower 1st and 2nd gears coupled with the 4.08:1 differential would be a stump puller with a rather harsh 1-2 upshift and speedometer problems. I want more off the line AND to get rid of some of that 30-50 mph sluggishness AND a reasonablly calibrated speedometer, so I came up with the above compromise. Any comments?

Keep talking...........you guys are great................John

[elwesso]

John.. i think your getting a little confused.

1. the J30 diff wont bolt into the car. Youll have to do quite a bit of work to get it to fit in there, more than with a skyline 4.08

2. You can turn the line pressure solenoid up a little when you take down the pan. I wouldnt worry about the 2-3 shift until you really have to.. Focus on other things... Thats a trick that people with level 10 transmissions have. Rob's went through that... It was too snappy at time, and they turned the line pressure solenoid down a little.. You can turn it a little more up to maybe counteract this..

3. 4.08 diff isnt going to make the trans shift any differently....

4. Youll be within 5% speedo error with 4.08 and J30 speedo sensor.. if you run 245-45-18, youll be down to around 1% (which even with correct diameter wheels, youll never notice).. Youll hardly even notice 5%, trust me!

[JohnPa]

John.. i think your getting a little confused.

1. the J30 diff wont bolt into the car. Youll have to do quite a bit of work to get it to fit in there, more than with a skyline 4.08

2. You can turn the line pressure solenoid up a little when you take down the pan. I wouldnt worry about the 2-3 shift until you really have to.. Focus on other things... Thats a trick that people with level 10 transmissions have. Rob's went through that... It was too snappy at time, and they turned the line pressure solenoid down a little.. You can turn it a little more up to maybe counteract this..

3. 4.08 diff isnt going to make the trans shift any differently....

4. Youll be within 5% speedo error with 4.08 and J30 speedo sensor.. if you run 245-45-18, youll be down to around 1% (which even with correct diameter wheels, youll never notice).. Youll hardly even notice 5%, trust me!

This stuff is all really good news! I'm headed to the wrecking tomorrow, so here's a few last questions:

1) Re. the J30 diff - I thought that for any of these diffs you simply (there's that word again) had to exchange the axle flanges (a circlip removal/repalcement operation) and exchange the input flange while installing a new crush sleeve and re-torquing the flang nut. Thus, I thought I could choose the J30 as easily as the 300ZX diff. Is the J30 diff really different or don't I understand the conversion process (more likely!)?

2) Any extra clues/posts you can direct me to on the transmission line pressure adjustment. That is the best news I've had for a long time!

Couldn't do this stuff without your help!

Thanks again..................John

[elwesso]

John i just dont know if the diff will physically fit into the subframe.. maybe it will, but i just dont know... the J30 diff is just like the 240 diff.....

You dont have to swap the axles out with a skyline diff.

[djessyjames]

if you still need a trans for your Q45 let me know , I have five (5) avalible, mileage on all of them is @ 100k 93-96 ....450.00 plus shipping