New rear end!
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From: SC
New rear end!
Hey guys, I have a 1996 F150 with a 351 and 32" tires, and it is a 4x4. I just had it at the shop to get the u joints replaced and found out that the rear-end is going out... needs new ring and pinion gears... I dont know anything about the gear ratio on it, but I was wondering since i have oversized tires, should I go with a different sized gear than stock? And does anyone know the stock gear size on my truck? Thanks for any advice or info. I figure it is best to find out a little about it before just having it done... Oh also, would it be worth it to find a complete rear-end at a salvage and try that out?
Last edited by PCWest13; Aug 16, 2006 at 05:04 PM.
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Joined: Mar 2002
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From: Bonita Springs FL
I would probably go with the salvage yard rear end. You can pick up an 8.8" axle for $100, and it will last another 10 years. Or you can spend $1000 rebuilding your current one. 
Just make sure you remove the inspection cover and make sure the gears aren't already worn out on it. Also check the pinion for play in every direction.
If you change the ratio in the rear, you have to have the front re-geared to if you want the 4x4 to be a useable feature.
Just make sure you remove the inspection cover and make sure the gears aren't already worn out on it. Also check the pinion for play in every direction.If you change the ratio in the rear, you have to have the front re-geared to if you want the 4x4 to be a useable feature.
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PCWest13
We would need more information about the axle then the year and make of the truck. Ford has so many differant flavors of gear packages then I could imagiane. There should be some sort of id tag stamped into the case. that will help.
As for going with a differant gear size, I would really recomend it. Bigger tires have more rotating mass, (something that most people dont think about when putting on larger tires.) This pusts more strain on the third member, so to relieve the strain go with a taller gear ratio maybe 4+ (ie 4.10, 4.25, or even a 4.80:1, please keep in mind it is the idea I am tring to convay, I dont think the actual ratios I have listed ar for fords.) You need to bear in mind case size for rear AND Front as they will liment you size that you can put in. You front and rear gears need to be with in .02 of each other (ie 4.08 in front and 4.10 in the rear, ok. 4.06 in front and 4.10 in rear, looking for major trouble.) Also, do the math and change tour speedo gear sor your speedomoter will be close to right. Hope this helps.
Brad
We would need more information about the axle then the year and make of the truck. Ford has so many differant flavors of gear packages then I could imagiane. There should be some sort of id tag stamped into the case. that will help.
As for going with a differant gear size, I would really recomend it. Bigger tires have more rotating mass, (something that most people dont think about when putting on larger tires.) This pusts more strain on the third member, so to relieve the strain go with a taller gear ratio maybe 4+ (ie 4.10, 4.25, or even a 4.80:1, please keep in mind it is the idea I am tring to convay, I dont think the actual ratios I have listed ar for fords.) You need to bear in mind case size for rear AND Front as they will liment you size that you can put in. You front and rear gears need to be with in .02 of each other (ie 4.08 in front and 4.10 in the rear, ok. 4.06 in front and 4.10 in rear, looking for major trouble.) Also, do the math and change tour speedo gear sor your speedomoter will be close to right. Hope this helps.
Brad
Post Fiend
Joined: Mar 2002
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From: Bonita Springs FL
Brad, in all likelihood, his truck has 3.55 gears. They could be 3.08's, but those are rare in 4x4's. Those are by far the two most popular factory ratios. I should have noted in my reply that he has to find out what his current gear ratio is and then shop for an axle based on that.
You can't really relieve strain on the third member by changing ratios. Bigger tires are hard on axles - you can't change that. There is also a carrier break in the Dana 44 at 3.92 - meaning if you cross that border, you need a new carrier as well as ring and pinion. Another cost to factor in.
The rule of thumb is that the front & rear have to be within 1.5%. I have seen factory gear ratios of 3.54/3.50. Tire wear and pressure make more of a difference than .4 ever will.
Also, he does not have a speedo gear, he has a VSS. You do not need to do anything to the speedo on his truck for a gear change, only a tire change. The VSS picks up revolutions of the ring gear, not the pinion or driveshaft.
You can't really relieve strain on the third member by changing ratios. Bigger tires are hard on axles - you can't change that. There is also a carrier break in the Dana 44 at 3.92 - meaning if you cross that border, you need a new carrier as well as ring and pinion. Another cost to factor in.
The rule of thumb is that the front & rear have to be within 1.5%. I have seen factory gear ratios of 3.54/3.50. Tire wear and pressure make more of a difference than .4 ever will.
Also, he does not have a speedo gear, he has a VSS. You do not need to do anything to the speedo on his truck for a gear change, only a tire change. The VSS picks up revolutions of the ring gear, not the pinion or driveshaft.
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Thanks andy for that infomation. I am still stuck in the old school of things and didnt realise that there is new ways to get speed from the transmission. thats cool. I have broke fewer pinions though by putting in a taller gear raito then going to a shorter one. maybe thats just my driving style dont know, But thanks for setting me straight.
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From: SC
Thanks for the help guys! I will make sure to verify the size of my gears that are in it right now and then start to shop around at the local yards. I will def. stay under the 3.92, because I dont have the extra cash to spend. Is this item sort of a failure item, meaning run it until its almost in the ground, then replace it? Right now I just get a loud clunk when I put it in reverse, I dont notice any whining or anything of that nature. I know the truck has been offroaded early in its life, but it only has 114,000 miles on it. Im guessing that even though the shop says its worn out, I can still squeeze a couple thousand more miles out of it while I do my shopping around...
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well only at your own risk and you are willing to fix whet ever the rear end breaks when it does, and i wouldnt take it muddin'.
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Post Fiend
Joined: Mar 2002
Posts: 19,402
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From: Bonita Springs FL
OK, I thought it was more grim than that.
I had the *exact* same problem with my 8.8 rear axle. Whatever shop you're taking it to is selling you something you don't need.
What's probably happened is that the pinion nut has backed off enough to allow play in the pinion. This is a common 8.8" axle problem. If you torque that nut back down - and it's not easy, it takes about 450 lb-ft - the play will disappear and you'll be fine again provided the pinion flopping around hasn't eaten the bearings already.
I had it done on my truck. That was about 10k miles ago, and it's been fine since. I won't replace it until it literally falls out from under the truck.
Good luck - and find a new shop!
I had the *exact* same problem with my 8.8 rear axle. Whatever shop you're taking it to is selling you something you don't need.
What's probably happened is that the pinion nut has backed off enough to allow play in the pinion. This is a common 8.8" axle problem. If you torque that nut back down - and it's not easy, it takes about 450 lb-ft - the play will disappear and you'll be fine again provided the pinion flopping around hasn't eaten the bearings already.
I had it done on my truck. That was about 10k miles ago, and it's been fine since. I won't replace it until it literally falls out from under the truck.
Good luck - and find a new shop!
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Thread Starter
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Senior User
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From: SC
That is great news... I will get it to a shop that can tighten it down ASAP so it doesnt do any further damage to the bearings. Howcome this is a common problem? Should the nut be checked for tightening ever so often? It seems like they would have used some sort of bolt that wouldnt back out with time...