2009 AWD flat tire - had to drive on slightly larger spare - harmful?

[mickeyaaaa]

2009 AWD flat tire - had to drive on slightly larger spare​

Had a flat on hwy (rt rear). Tire is trashed. put spare on, but the tires on truck are on 20" factory wheels, fairly worn and the spare is factory new full size tire on an 18' steel, but they are roughy specced at same overall diameter...but there is a slight diameter difference. Owner manual says just not to exceed 113 kph with full size spare....not much help.
Now after putting spare on, when accelerating i get the odd jerk or hesitation 2-4 times around 40-70kph and then once my speed levels off its fine. is this maybe AWD kicking in detecting the diameter difference as if it were tire slipping?
Am I doing harm? I had little choice but to drive today and 600kms tomorrow to get home. Irony is i was going to swap my winter wheels/tires on this weekend lol...

 

[mickeyaaaa]

well, like i said really didnt have much choice so i drove the 600km home with the slightly larger spare....odd jerk on acceleration but once at hwy speed no issues. putting my winter tires on today so i guess i'll find out if anything is damaged soon enough...

Found this post but it was referring to a 1997. not sure if my 2009 AWD same rules apply:

December 9, 2020 #8 You should no matter what, maintain the exact same diameter(total) tires front to rear, new or used. So either repair the old one without driving the vehicle with non matching tires, or buy a different set, again without driving it any distance with a non matching tire. The AWD must have the same front and rear total diameter tires.....The front and rear driveshafts must spin at the same rpm, the AWD will fight any change of that. If they don't match, the AWD will create heat as it fights to keep them the same. That is what ruins the viscous clutch. Don

 

[Bazz270]

There is no viscous clutch in gen4.
And yes.the tires to be exactly the same or transfer/brake system damage will occur

 

[Fix4Dirt]

well, like i said really didnt have much choice so i drove the 600km home with the slightly larger spare....odd jerk on acceleration but once at hwy speed no issues. putting my winter tires on today so i guess i'll find out if anything is damaged soon enough...

Found this post but it was referring to a 1997. not sure if my 2009 AWD same rules apply:

December 9, 2020 #8 You should no matter what, maintain the exact same diameter(total) tires front to rear, new or used. So either repair the old one without driving the vehicle with non matching tires, or buy a different set, again without driving it any distance with a non matching tire. The AWD must have the same front and rear total diameter tires.....The front and rear driveshafts must spin at the same rpm, the AWD will fight any change of that. If they don't match, the AWD will create heat as it fights to keep them the same. That is what ruins the viscous clutch. Don

viscous clutch applies to the awd 4404 2nd gen v8s. these have a different tcase, but the same advice should still be followed for an awd

 

[mickeyaaaa]

viscous clutch applies to the awd 4404 2nd gen v8s. these have a different tcase, but the same advice should still be followed for an awd

thx, this is a 2009 4.6 v8, AWD, with i believe 4412 tcase, now I know it is electronically controlled clutch but for this discussion it appears it makes no difference.

oh man, im really stressing now...hope theres no damage...drove approx 900 kms like this.

I'll be putting my good winter set on today.

What's the way to test to know for sure if my AWD is still working correctly?

 

[Bazz270]

Put on high and low transfer mode

Go light off road and see if no any strange noises or vibration detected on both modes.

If still feel smooth then everything is probably ok

 

[mickeyaaaa]

Put on high and low transfer mode

Go light off road and see if no any strange noises or vibration detected on both modes.

If still feel smooth then everything is probably ok

This is pure AWD version, no 4x low, no buttons....but in the menus there is a way to "lock" for 50/50

- UPDATE: TRIED IT AND AWD IS STILL WORKING PROPER!! thank goodness...
Edit: probably important to note, i measured the wheel circumference when i swapped over to winters. the spare was only about 10-20mm smaller circumference than my summer tires...a bigger difference I'm guessing would increase the risk of damage.