2nd gear is a bit hard to use when cold

[Patrol'n]

G'day guys,

I have the RB30 with 5 spd manual box in my 93 patrol, my question is, that 2nd gear seems a bit stiff / hard to select / crunchy when cold. This usually lasts a few minutes, then once everything warms up all is perfect. No other gears seem an issue. I know it ain't new, and that second is often the hardest worked gear, and I've had manuals before that get a bit cranky when they get old, but the way this settles down once warm, not sure what the problem, or best fix is.

I did think of changing the gearbox oil to a thinner / lighter oil, but I'm not sure if that's a good idea with these boxes. Some of my old Isuzu boxes years ago I used to use premium synthetic engine oils with good results, (although I'm not making any official recommendations to do this, since I don't know if it's good for them, but worked for me).

Any ideas anyone?

Thanks heaps.

Cheers.

[NP99]

My 4500 does the same. One of the many jobs on my list is to drain and refill and see if there's an improvement.

[mudnut]

I have an RB30 and have recently had to pay someone to change out the gear box. Unfortunately, the new (2nd hand) gear box is crunching in 2nd gear when it is cold, as well. I have learned to double-clutch until the oil warms up. (usually 3-4 klm) It changes smoothly after that.

The RB30 box specifies using a AGL4 oil not AGL5.

The mechanic who put the box in has put AGL5 in mine and has suggested trying a 50% mix with auto trans fluid. He reckons the trans fluid will sit on top of the gear oil and will lubricate the box, until the gear oil thins down. I don't like this idea at all and will drain and fill the box with a lighter grade AGL 4 oil when funds permit.

Another mechanic thinks that the clutch may not be disengaging properly, when cold.

[NP99]

I have an RB30 and have recently had to pay someone to change out the gear box. Unfortunately, the new (2nd hand) gear box is crunching in 2nd gear when it is cold, as well. I have learned to double-clutch until the oil warms up. (usually 3-4 klm) It changes smoothly after that.

The RB30 box specifies using a AGL4 oil not AGL5.


The mechanic who put the box in has put AGL5 in mine and has suggested trying a 50% mix with auto trans fluid. He reckons the trans fluid will sit on top of the gear oil and will lubricate the box, until the gear oil thins down. I don't like this idea at all and will drain and fill the box with a lighter grade AGL 4 oil when funds permit.

Another mechanic thinks that the clutch may not be disengaging properly, when cold.

I think the grade 5 oil wears the box internals, hence why grade 4 is recommended.

[mudnut]

There is a thread dealing with that issue, but my understanding is that the 5 AGL additives are tougher than the brass they coat, so when they are abraded off, they take a bit of brass with them. The manufacturers of newer oils are supposed to have dealt with that, so I have been told, but I will go back to a 4AGL, Justin Case.

[Patrol'n]

I have an RB30 and have recently had to pay someone to change out the gear box. Unfortunately, the new (2nd hand) gear box is crunching in 2nd gear when it is cold, as well. I have learned to double-clutch until the oil warms up. (usually 3-4 klm) It changes smoothly after that.

The RB30 box specifies using a AGL4 oil not AGL5.

The mechanic who put the box in has put AGL5 in mine and has suggested trying a 50% mix with auto trans fluid. He reckons the trans fluid will sit on top of the gear oil and will lubricate the box, until the gear oil thins down. I don't like this idea at all and will drain and fill the box with a lighter grade AGL 4 oil when funds permit.

Another mechanic thinks that the clutch may not be disengaging properly, when cold.

Interesting you say that about the double clutching, that's exactly what I've been doing. I reckon I'll go and get some AGL 4 this weekend and swap it out to see if that helps it.

(Hope the gearbox is healthy enough otherwise)....

Thanks gents

[Patrol'n]

One other thing worth mentioning, I don't know if anyone else has priced up reco gearboxes, but I've seen them advertised on ebay as exchange units for about $1200 or so, (yeah still pricey, but cars tend to be like that), didn't check the freight cost though.

[92GQ]

The difference between GL-4 and GL-5 is huge in these boxes, as mentioned, GL-5 wears on the brass components in both the RD28/RB30 and TB42/TD42 boxes, it also makes it very hard to select gears.

I run the below in mine, gearbox runs great.

Penrite Pro Gear 75W-85 Full Syn

[threedogs]

Is it worth adding an additive like Moreys or Nulon?
Or better to just use the right oil,

[mudnut]

The right oil, TD. It is just a lack of funds that I haven't done it yet.