1986 FORD F-150 GEAR SIZES?

  • Tiny
  • DavidAustin
  • 1986 Ford F-150

Hello,

I have a 1986 Ford F-150 4x4 that originally had 354 gears in the front and 355 in the rear. I tore the rear gears up a while back, and I have a spare rear differential that has 350 gears. Would this work in the rear? That would give me 354 in the front and 350 in the rear. Would the 4x4 work correctly without any problems? That's a difference of "4" where originally it was a difference of (2).

Thanks, Lewis D. Austin

Tuesday, October 15th, 2013 AT 6:51 AM

6 Answers

  • Tiny
  • hmac300
  • Expert
  • 41,622 posts

When you put it in 4 wheel drive it may wind up the t-case a tad more and be hard to get out of 4wd. You would have to back up to see if it would unwind then. But it may not do it as it's pretty close.

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Tuesday, October 15th, 2013 AT 7:02 AM
  • Tiny
  • DavidAustin
  • Member

So, if the transfer case will unlock out of four wheel drive when backing up, then, I should be fine?

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Tuesday, October 15th, 2013 AT 7:06 AM
  • Tiny
  • hmac300
  • Expert
  • 41,622 posts

It might do what I said but it should unwind and gout of 4wd when backing up.

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Tuesday, October 15th, 2013 AT 7:07 AM
  • Tiny
  • DavidAustin
  • Member

Ok, so, it shouldn't be any problems with damage to either of the differentials or transfer case? In other words, the difference in ratio of gears of one differential catching up to the other and causing damage.

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Tuesday, October 15th, 2013 AT 7:11 AM
  • Tiny
  • hmac300
  • Expert
  • 41,622 posts

Look you have almost a 30 yr old truck if you are that unsure of damage then replace it with the correct gear. All older model trucks used to get tcase wind up due to difference in gear ratios. The rear end would be the last thing to get damaged the tcase would get damged first which I don't think it would due to the close gear ratio. If it's in 4wd for a short time it probably wont' due that.

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Tuesday, October 15th, 2013 AT 7:14 AM
  • Tiny
  • DavidAustin
  • Member

Ok. Thanks so much, I appreciate your help and patience. Take care.

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Tuesday, October 15th, 2013 AT 7:16 AM

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