Changed rear diff fluid and greased drive line, now trans runs hot

S

Skunkworks

New member
What is going on? I changed out the rear diff fluid today with Valvoline synthetic 75-140 because 75-90 wasn't on the shelf. I took it for a test drive and wanted to be sure the diff plug wasn't leaking at operating temp. According to my OBD II, The transmission reached 194 deg when I never saw it above 180 before and usually right about 170 for normal driving. I also greased the drive shafts. Any insight?
 
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The 75-140 will definitely make your engine and trans work harder because...thickness. I once put it in the rear diff of my 22RE '91 Toyota 4WD truck, and the top speed on the freeway got slower.
BTW, you'll probably notice a decrease in mileage.
 
In addition to the thicker oil, I think it’s possible to over-grease the sliding yoke and put a temporary bind in it. Maybe that?
 
thennen said:
In addition to the thicker oil, I think it’s possible to over-grease the sliding yoke and put a temporary bind in it. Maybe that?
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That would be my guess. Going to a thicker gear oil shouldn't changes things that much.

I would remove the slip yoke, clean out all of the excess grease and lightly "paint" fresh grease on the splines. Remove the zerk fitting and re-install it, this will allow air to escape.

Do not use the zerk fitting on the slip yoke in the future. All it does is pump grease at the bottom of the slip yoke and binds it up. Your best bet is to just remove it every year or so and clean/re-grease as I described above.
 
thegipper said:
That would be my guess. Going to a thicker gear oil shouldn't changes things that much.

I would remove the slip yoke, clean out all of the excess grease and lightly "paint" fresh grease on the splines. Remove the zerk fitting and re-install it, this will allow air to escape.

Do not use the zerk fitting on the slip yoke in the future. All it does is pump grease at the bottom of the slip yoke and binds it up. Your best bet is to just remove it every year or so and clean/re-grease as I described above.
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Thanks for the advice! Is there a tutorial on how to remove the slip yoke like you describe? I'm not afraid of wrenching, but I'm not sure how to do that w/out messing things up.
 
All Good now it seems. I changed to 80-90 oil. I also took the zerk off the slip yoke and jumped up and down on the bumper really hard (I'm fat too ;-) ) and the transmission temp didn't go higher than about 165 at 70mph now and stayed closer to 150 under normal driving at 60mph. I'll still be changing my ATF pretty soon as it hit 200 for a short while and I'm not sure when it was changed last. I've had the truck for about a year.
Thanks for the help all.
 
Skunkworks said:
All Good now it seems. I changed to 80-90 oil. I also took the zerk off the slip yoke and jumped up and down on the bumper really hard (I'm fat too ;-) ) and the transmission temp didn't go higher than about 165 at 70mph now and stayed closer to 150 under normal driving at 60mph. I'll still be changing my ATF pretty soon as it hit 200 for a short while and I'm not sure when it was changed last. I've had the truck for about a year.
Thanks for the help all.
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To add a little perspective, I over-greased my 1988 Runner more than once. Never experienced a drivetrain problem. The grease eventually worked its way out and slung all over the undercarriage and the ground. No, I don’t recommend my uneducated method, but I think Toyota made their drivetrains difficult to break by simply over-lubricating. So I think you’re safe.
 
Skunkworks said:
I'll still be changing my ATF pretty soon as it hit 200 for a short while and I'm not sure when it was changed last.
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200*F will not cause the transmission to blow up! The idiot light on the dash for trans temp is around 280*F. You don't want to regularly be running above 200*F, but there are millions of vehicles out there running over 200*F for periods here and there with no damage.

If you don't know the maintenance history, changing the fluid is a good idea - just to get a baseline...

-Charlie
 
phattyduck said:
200*F will not cause the transmission to blow up! The idiot light on the dash for trans temp is around 280*F. You don't want to regularly be running above 200*F, but there are millions of vehicles out there running over 200*F for periods here and there with no damage.

If you don't know the maintenance history, changing the fluid is a good idea - just to get a baseline...

-Charlie
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I think people are going overboard with being concerned with transmission temperatures around here. There are probably a significant amount of 3rd gen 4runners still roaming around with significantly less maintenance ever been done to them and the transmission will still shift just fine.

Change your fluid every 60-90k miles and move on. Toyota made these things to go off-road and such, they aren't fickle Ferraris.
 
Skunkworks said:
All Good now it seems. I changed to 80-90 oil..
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East Coast Gear Supply requires you to run 85-140 non-syn as break in lube for warranty on work to be good.
The lube you had was good to use, I stayed with 85-140 after break-in both diffs and transfer case.
 
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