spider gears damaged - how bad is this?

mostsmooth

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Nov 12, 2002
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Hi all,
pics below.
95 gt heads/intake/cam/supercharger for about 95% of its 140k+ miles. supercharger no longer on car.

I am in the process of changing my differential oil. I didn't hear any noises or anything, just changing it out of due diligence since I am getting the car back into shape.
drained it out and took a look at the gears inside.
found at least a few teeth on the spider gear are obviously damaged. I don't know how to rotate them to see the rest of the teeth (other than taking everything apart, which I'm not prepared to do at this time).
I also found what appears to be some wear marks on the ring gear.
I don't want to say the word 'slop' and trigger the wrong responses, but there may be some slop in the gears. not sure. I could rotate the tire about 0.5 inches before the ring gear moved it seems. I was watching some youtube videos last night and now I'm paranoid. I would be surprised if the guy who put the gears in (in 1995/1996 or so) went through all that appears to be the necessary steps.

I have been driving the car for a few weeks now and didn't seem to have any problem with the differential. if I didn't start the change procedure, I would still be driving the car as is.

so, I know that these should be replaced I guess, questions below:

1. seems I need to replace the spider gears for sure, but the ring gear seems ok, or do they all have to be replaced as a set?

2. as I mentioned, I would be driving this around oblivious if I hadn't checked, so how bad is this if I keep driving it until I find somebody to do the work?

3. is this wear pretty typical after 140K+ of hard miles?

4. car currently has 3.73 gear set, I don't necessarily love driving around with 3.73s, but I can live with it. this seems like it may be a perfect opportunity to replace the 3.73s with 3.55s maybe but the cost may be prohibitive to do it if it's not needed. so, does anybody know how many hours of labor it typically would take to A. replace just the spider gears and B. replace spider and ring and pinion gears? I don't want to spend like $1500 or whatever to replace everything if I could spend $300 just to replace the spider gears. Seems there is a lot of work involved with replacing ring and pinion gears.

thanks
 

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7991LXnSHO

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You could put it back in service with new oil until it whines, grinds and self destructs. Besides the fun of tearing stuff up, and maybe some time to look for a better replacement, I would not put this into use without rebuilding.
 

Andrews24

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I myself would replace it all once I’m in there. If you are on a budget you could reuse that ring gear - that carrier needs replaced
 

2000xp8

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With 140k miles, they only thing i'd be re-using is the axles and the housing.
Remember, the metal from those teeth went somewhere.
Looks like at lmr a spider gear rebuild kit is $200. Then you have to pay someone to rebuild it and hope they do a good job.
I really can't see leaving the bearings with metal floating around in the rear either.
 
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nickyb

WAIT,you now have a pair?
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If it was my rear end ( no c.t. Please) I would get a complete One from the pic a part. Then you could swap to your preferred ratio gears when funds are aval.
 
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7991LXnSHO

wanna catch the space herp
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It’s already started to blow chunks. You caught it before it stranded you.
A family business work van was driven until it had to be occasionally pushed a bit to be able to go anywhere. It ran ok, but it was missing ring gear teeth. The shop was shocked it drove in. Don’t maintain vehicles like my grandpa.
 

mostsmooth

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thanks all for the thoughts

three more questions:

1. replacing the guts of the differential, is this something a typical mechanic can do successfully, or do I need a ford mechanic or a mechanic that just works on mustangs or? i will talk to my regular guy and see how he feels, but just curious what you folks who cant do this sort of thing on your own feel about it.

2. looking at LMR, I see various kits. this is the route I would probably go as the pic a part or junk yard or whatever thing will be too much of a hassle for me I think. it seems I would need something like these three kits:

does that look about right? or do they sell a kit that has everything in there i need?

3. I was watching some vids on how to do the ring and pinion install, and the guy bought an extra bearing (i think that's what it's called) for the pinion and he ground out the inside a little so he could slip it on rather than press it on and then he used it to set up the ring and pinion and then put the other new one on once he had it set up correctly. this was an alternative to pressing on the 1 and then taking it off and adding shims and pressing it back on apparently. is this standard procedure?

thanks again
 

mostsmooth

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hmm, one other thing, i am under the impression the stock axles on 95 gt is 28 spline, maybe it makes sense at this point to upgrade to 31 spline?
 

nickyb

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You don't need 31 spline axles unless you are going for John Force burn outs and red line launches with high h.p.
Those parts cover what you need, just take it to a shop that sets up rear ends.
 

2000xp8

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You may not need 31 spline axles, but they would allow you to buy the cobra rear traction loc, which is only like $250-$275.
Instead of rebuilding the stock 30 year old unit at $200+labor.
So if you can get the axles a decent price, i would say do it.

The rear should be done by someone that knows how to build a rear if you want it to last another 140,000 miles.
 

Willybill32

But at least it's tight!
Jul 16, 2019
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Hi all,
pics below.
95 gt heads/intake/cam/supercharger for about 95% of its 140k+ miles. supercharger no longer on car.

I am in the process of changing my differential oil. I didn't hear any noises or anything, just changing it out of due diligence since I am getting the car back into shape.
drained it out and took a look at the gears inside.
found at least a few teeth on the spider gear are obviously damaged. I don't know how to rotate them to see the rest of the teeth (other than taking everything apart, which I'm not prepared to do at this time).
I also found what appears to be some wear marks on the ring gear.
I don't want to say the word 'slop' and trigger the wrong responses, but there may be some slop in the gears. not sure. I could rotate the tire about 0.5 inches before the ring gear moved it seems. I was watching some youtube videos last night and now I'm paranoid. I would be surprised if the guy who put the gears in (in 1995/1996 or so) went through all that appears to be the necessary steps.

I have been driving the car for a few weeks now and didn't seem to have any problem with the differential. if I didn't start the change procedure, I would still be driving the car as is.

so, I know that these should be replaced I guess, questions below:

1. seems I need to replace the spider gears for sure, but the ring gear seems ok, or do they all have to be replaced as a set?

2. as I mentioned, I would be driving this around oblivious if I hadn't checked, so how bad is this if I keep driving it until I find somebody to do the work?

3. is this wear pretty typical after 140K+ of hard miles?

4. car currently has 3.73 gear set, I don't necessarily love driving around with 3.73s, but I can live with it. this seems like it may be a perfect opportunity to replace the 3.73s with 3.55s maybe but the cost may be prohibitive to do it if it's not needed. so, does anybody know how many hours of labor it typically would take to A. replace just the spider gears and B. replace spider and ring and pinion gears? I don't want to spend like $1500 or whatever to replace everything if I could spend $300 just to replace the spider gears. Seems there is a lot of work involved with replacing ring and pinion gears.

thanks
There’s not a whole lot of difference between the 3.73 and the 3.55. If you’re not wild about the 3.73, maybe a drop to 3.27?
 

90sickfox

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Those spider gears were set up way too tight. Means the clutch pack shimming probably isn't right. That metal could be anywhere and everywhere in the rear. Id replace the axle bearings, seals, and all the guts of the rear.

If it wasn't making noise or clicking around tight turns I d put it back together and drive until you can build up replacement parts. A whole rear would be nice and can be found at a reasonable price used. You know how to pull the cover and what damage to look for. If you aren't racing the car then a stock rear would be fine.
 

LILCBRA

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As far as your ring gear goes, I wouldn't be afraid to reuse it or the pinion bearing. But if you want to change gearing, now would be a good time to do it. Personally, I think I'd see if I couldn't get a "new" r&p from a salvage yard, order the install kit, then I think I'd spend the money on one of these:


I just installed one in my truck and love it so far. Of course it's not going to be the cheapest route, but I think it would probably end up outlasting a lot of other parts on the car over it's lifespan. After having dealt with installing one in my truck, I think this is the route I'm going to take for my vert. :)

Having someone do the work for you will only jack the price, but on the same token if you're not comfortable with it or lack the skills and tools, I'm sure it'll be cheaper in the long run. Like I said, I just installed this in my truck, I probably spent a good $500 on new tools that I needed that I didn't already have. :shrug: So in my case with my truck, I probably spent around $1300 (~$500 for the differential, ~$200 for the install kit, ~$75 gear oil, ~$500 new tools), and I had my truck down for a little over a week. So, if you look at it like that, $1500 doesn't sound all that bad for a shop who knows what they're doing and has all of the required tools that will probably only have it for a couple days.

To answer question #4 about the pinion bearings and shims and such, some people do it that way, some don't. The purpose of the shim(s) is to set the correct mesh of the gears by setting a proper depth of the pinion gear, but that is mainly due to machining tolerances of the housing. If you're using the old r&p it's almost as easy to just reuse the shim, most of the time it'll be set right. When installing a new pinion gear is where you'd want to be able to slip the bearing on and off easily to shim as necessary since you don't know what the machining tolerances are in comparison. There are a few different ways that this could be checked before the pinion is installed - depth mic the existing pinion gear while it's in the housing, then after it's removed mic the pinion gear "face" to the face of where the bearing seats, add whatever shim thickness that it might have, and compare those measurements to the new pinion and shim accordingly, OR by trial and error like the video you watched. Most mechanics don't have all of the precision tools needed to do it the way I first described so they're relegated to the second option. Another option - instead of shimming behind the pinion bearing, the shims could be installed behind the race since that's a bit easier to remove and replace. That will also depend on the pinion gear, though, as the crush sleeve will need to set proper preload on the pinion bearings. As long as there is sufficient pressure on the bearings and the contact pattern is good, shim placement really doesn't matter.
 

mostsmooth

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Hi all,
thanks for those latest replies.

i appreciate all the responses.
i understand the thought behind the 'there's metal floating around you should replace everything', and i am not disagreeing or dismissing it, however:

this is not my daily driver, and i have AAA, and if I am willing to gamble, is it stupid that i just replace the top and bottom gears and roll the dice? (the side gears stay as far as i know, right?) worst case is i do that and it grenades in a month and i replace everything anyway. less of a worst case is next year when i change the differential fluid again i see some similar or less damage and revisit. to be honest, if i could sign up for just having to replace those two gears every few years if at all, i would be fine with it. best case would be i change the fluid next year and everything looks fine.

and, i think i am correct but not sure, the top and bottom gear, i just rotate the tires until the bolt that holds that center pin in place is accessible and i unscrew it, take out the pin, and pop out the gears, right? that is something I can do on my own. hmm, there is that spring in the middle, that might ruin that plan, would i need some special tool for that?

i am not prepared to get a press and tackle setting everything up correctly.
i will still consider having it professionally done, but I have issues with stress, and the whole idea of dropping off my car and worrying about if it's getting done right would be traumatic. the thought of getting it back and there's noise's and having to go back and argue with folks, yikes, not a fan. arguing isn't a problem its just the entire hassle of it all. yes, that stress would be way more than any stress from me thinking about my differential grenading because i didnt replace everything.

regarding the setup being too tight, i have no way to tell but lets say it is, it lasted a long time that way, if replacing these top and bottom gears (top and bottom in the pic, i believe they move around when the car turns) buys another 20k+ miles, i could live with the setup being tight i think.

i did look up the shop that did some engine work for me a while back but it seems they closed. I would have let him do it with no worries.

money isnt a real issue, i just dont like spending it if i dont have to. I would rather have the extra $1200 in my pocket and take my chances (partially because the downside doesnt appear to be too much worse than where im at now)

feel free to flame me if need be :)

thanks again
 

7991LXnSHO

wanna catch the space herp
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Running it until it blows big chunks is a possibility I mentioned off the top. The only way that would not be stressful to me is because I had a newer rear end assembly in the works or ready under the bench.
 
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General karthief

wonder how much it would cost to ship you a pair
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Clean it out as good as you can, stuff some new spider gears in it and send it down the road,
Oh, don't forget the gear oil, just off the shelf stuff with some friction modifier, no need for anything special.
You may be surprised.
JMO
 
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mostsmooth

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Clean it out as good as you can, stuff some new spider gears in it and send it down the road,
Oh, don't forget the gear oil, just off the shelf stuff with some friction modifier, no need for anything special.
You may be surprised.
JMO
i already cleaned it out, and put in some motorcraft 80/90 and 4oz of friction modifier. i took it around the block gently just to get the oil circulated on the internals that i cleaned and it has been sitting since. didnt hear anything strange.

i will probably talk a mechanic or two and weigh the options.

thanks all again