Replacing Trans & Diff Fluid, Hot vs Cold - Toyota GR86, 86, FR-S and Subaru BRZ Forum & Owners Community

BRZNutt · 12-08-2013, 01:20 PM

I am going to change my manual transmission and rear differential fluid soon. Should I let the car sit overnight to ensure all the crap is at the bottom when it drains out? Or do it after the car has been driven for a few miles to warm up the fluid and make it flow better? I've been reading all the treads on changing out your trans fluid, but didn't seem to get a general consensus from how everybody has been doing it.

Philly758 · 12-08-2013, 03:24 PM

I've always changed oil and fluids when warm so they flow better, but I am far from an expert. I'd be interested to see what a real mechanic has to say about this.

Ralph Spoilsport · 12-08-2013, 06:32 PM

Do it warm.

humfrz · 12-09-2013, 11:36 AM

I don't think it much matters.

humfrz

Fizz · 12-10-2013, 12:29 AM

Be careful not to do it immediately after a drive as the oil can be very hot. If your car has been sitting overnight just take it for a short 5-10 min drive, then go back and have a cup of tea before you start the job. It should cool down nicely but just warm enough for the oil to flow better.

Realistically I don't think it matters even if you did it cold....the differences will be negligible.

BRZNutt · 12-13-2013, 08:34 AM

Thanks for feedback. I'll do it when it is warm.

Krispeee · 12-13-2013, 05:34 PM

Drain oil while warm as it flows better. Wear gloves and safety goggles just to protect yourself.

way too fast motorsports · 12-21-2013, 09:01 PM

warm is easiest, also helps to warm up the new fluid before you pump it in makes life easier. i use a construction spot light to warm up the bottles before i put them in

shawnhayes · 12-22-2013, 09:04 PM

Service experts all agree that changing splash fluid reservoirs should be done before the particulate matter has time to settle.

Cold or hot is immaterial, but if drained right after running, this is mostly hot. The fluid will drain and fill quicker if hot, but that is simply a convenience detail.

Otherwise, there is the possibility that some of the contaminants will have "settled" somewhere in the diff that won't easily drain off. Having done this just last night on my Impreza at 10,000 miles, there may be A LOT of contaminants in this differential.

Shawn

Sent from my iPhone using Tapatalk

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12-08-2013, 03:24 PM	#2
Philly758 Senior Member Join Date: Jan 2013 Drives: GMC Location: NY Posts: 258 Thanks: 76 Thanked 45 Times in 29 Posts Mentioned: 3 Post(s) Tagged: 0 Thread(s)	I've always changed oil and fluids when warm so they flow better, but I am far from an expert. I'd be interested to see what a real mechanic has to say about this.

12-08-2013, 06:32 PM	#3
Ralph Spoilsport Senior Member Join Date: Aug 2013 Drives: 2013 BRZ, WRB Location: Galt's Gulch, NH Posts: 225 Thanks: 107 Thanked 207 Times in 93 Posts Mentioned: 1 Post(s) Tagged: 0 Thread(s)	Do it warm.

12-09-2013, 11:36 AM	#4
humfrz Senior Member Join Date: May 2013 Drives: 2013 FR-S, white, MT Location: Puyallup, WA Posts: 29,869 Thanks: 28,791 Thanked 31,816 Times in 16,425 Posts Mentioned: 708 Post(s) Tagged: 2 Thread(s)	I don't think it much matters. humfrz

12-10-2013, 12:29 AM	#5
Fizz Senior Addict Join Date: Jan 2013 Drives: 86 GT Location: Perth, Australia Posts: 1,217 Thanks: 249 Thanked 336 Times in 215 Posts Mentioned: 12 Post(s) Tagged: 0 Thread(s)	Be careful not to do it immediately after a drive as the oil can be very hot. If your car has been sitting overnight just take it for a short 5-10 min drive, then go back and have a cup of tea before you start the job. It should cool down nicely but just warm enough for the oil to flow better. Realistically I don't think it matters even if you did it cold....the differences will be negligible.

12-13-2013, 05:34 PM	#7
Krispeee Senior Member Join Date: Sep 2013 Drives: 2013 Subaru BRZ Limited Location: NorCal Bay Area Posts: 298 Thanks: 175 Thanked 119 Times in 92 Posts Mentioned: 9 Post(s) Tagged: 0 Thread(s)	Drain oil while warm as it flows better. Wear gloves and safety goggles just to protect yourself.

12-21-2013, 09:01 PM	#8
way too fast motorsports Member Join Date: Dec 2013 Drives: V8 Miata Location: Venice Posts: 13 Thanks: 0 Thanked 6 Times in 4 Posts Mentioned: 1 Post(s) Tagged: 0 Thread(s)	warm is easiest, also helps to warm up the new fluid before you pump it in makes life easier. i use a construction spot light to warm up the bottles before i put them in

12-22-2013, 09:04 PM	#9
shawnhayes Member Join Date: Aug 2013 Drives: 2013 Pearl White BRZ Limited Location: Earth Posts: 27 Thanks: 6 Thanked 29 Times in 16 Posts Mentioned: 0 Post(s) Tagged: 0 Thread(s)	Service experts all agree that changing splash fluid reservoirs should be done before the particulate matter has time to settle. Cold or hot is immaterial, but if drained right after running, this is mostly hot. The fluid will drain and fill quicker if hot, but that is simply a convenience detail. Otherwise, there is the possibility that some of the contaminants will have "settled" somewhere in the diff that won't easily drain off. Having done this just last night on my Impreza at 10,000 miles, there may be A LOT of contaminants in this differential. Shawn Sent from my iPhone using Tapatalk

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