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Discussion Starter #1 (Edited)
hey I was looking at putting 3.73 gears in my 3.8 na, but I was wondering how much a shop would charge to do this (in the NJ area).

I looked in summit racing and 3.73 gears cost $205.95 (Richmond most expensive) or the summit racing brand for $142.95...

Just want to price it out before I go for it.
Thanks for any help guys.
 

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You could try calling local machine shop's around your area and getting an estimate. Each shop sorta has their own labor rates and such. If your switching from stock to 3.73, you are going to have to get your ecm tuned for those gears too. I'm sure other's will follow in behind me with more details, you can even :search:, this has been asked quite a bit. I'm just replying with a short summary answer, as I gotta go finish waxing my car :)
 

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Discussion Starter #3
lol thanks i wish i could be waxing my car been raining all day. i tried the search for "3.73" and "gears" and it comes up with nothing... oh well see what others say and I will call around and post my findings...

also yes it would be going stock to the 3.73s and I was planning on getting a chip after the gears are done but probably wont be able to do it right away
 

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If your car doesn't already have the "two wheel peel" option, it might be a good time to add it right along with the new gears. Have it opened, installed, set up, closed back up, new fluid, and labor paid once.

Just a thought. :thumbsup:
 

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lol thanks i wish i could be waxing my car been raining all day. i tried the search for "3.73" and "gears" and it comes up with nothing... oh well see what others say and I will call around and post my findings...

also yes it would be going stock to the 3.73s and I was planning on getting a chip after the gears are done but probably wont be able to do it right away
Yes, like 94 Thunderbird LX said, if you don't have a Trac-Loc differential, now may be a nice time to try and grab one.

Anyways, while I was searching for some information for you, I noticed that you posted under General Tech. If you try looking under Drive Train, and then Differentials, you might find some valuable information. Let me know your findings for the prices too, as I am looking to doing a 3.73 swap. Even tho I am broke, haha.
 

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Discussion Starter #6
ok so I found that you do need a tune, and you need to switch from the green speedo gear to the purple one...
on the other note how do you switch to trac-loc and pricing? as I would prefer that anyways...
i have started finding a bit more on searches, but still haven't found any rough pricing
 

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Discussion Starter #7
also some posts have me thinking whether 3.73 or 4.10 is more desirable
 

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Gears, especially IRS are a bit tricky. You need to find someone experienced with them. The closest person I know to you would be RobertP.
I would avoid "generic" gears as I have had problems before. I buy gears from and parts from supercoupe performance. He is local to me and sell the Yukon gears which have given me the best overall results for noise and ease of install. Motive and richmonds are nice but a bit harder to get shimmed correctly as the pinion depth gauge I have doesn't work on them.
Alan
 

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When I installed 3.73's in my 92 3.8 T-Bird I only changed the speedo gear. Definetly makes the car more enjoyable. Dpending on what type of driving you do (highway or city) which gear set you should use.
 

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Discussion Starter #10
i do both is the thing mainly i use to do only town/city type driving but now i have a bit of a commute to work and am on back roads and a bit highway... what are the major differences between the 3.73 4.10 in feel... are 4.10s really going to hurt fuel economy on the highway? Do 3.73 have enough of a punch? I'm looking to make the thunderbird a bit quicker as i dont know when i'll be getting my 67 mustang back (its been in the shop for almost a freakin yr!) and would really like a more sports car type ride, but thats just me
 

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Both will affect fuel mpg. I installed 3.73 (they were free) because 4.10 was to much for my drive. I did drive 50 mil one way , mostly open road. The 3.73 made acc from a dead stop better but I liked the ability to pass faster or better when at speed. You need to watch out for running the rpm up to high and to long. You get more wear on the motor and trans(higher rpm's). Also the 3.8 head/head gasket can cause a problem.
 

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Discussion Starter #12
ok so this is what i'm pretty sure i'm going to do...
trac-loc and 4.10 gears (so what parts do i need to do this?)
i already have a trans-go shift kit and cold air... otherwise the car is still stock

now two things i read on one post that prior to 94 the tranys were not computer controlled which i know from shift kitting mine, so therefore it was said you do not need a tune, just the new speedo gear...
also how do i make sure i have a 8.8 rear because i am reading in some places that some tbirds had 7.5 rears
 

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I think the gear size is cast into the housing on the pumpkin; at least, I can see "8.8" molded into the bottom right quarter of the rear on mine.
 

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If you've got a 3.8, then odds are very very good (like 98%) that you have a 7.5. BUT if you can find a worn out, used 8.8 trac-loc at a salvage yard you can have it rebuilt with whatever gears you want, and it should bolt right in.
 

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Discussion Starter #15
ok thats what i figured... what would i need to put from the yard to switch to the 8.8? and which cars had the 8.8s that would bolt in? would i be better off just buying a new one and switching out the 7.5?
 

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All I did was find a worn out 8.8 at a salvage yard (odds are you're going to have it rebuilt when putting the new gears in anyway). I think I got a 3.27 trac-loc for about 75 bucks. then I bought the two rebuild kits (one for the Trac-loc unit, the other for installing everything in the case), found a set of gears on Ebay and took all the parts to a guy here in town that was highly recommended.

He put everything together into a nice set of 3.73's for me. (of course, I also gave him a Mark VIII case to put those parts into, but thats just an optional extra expense, not necessary)

I think all you need is the 8.8.. I think it'll bolt right in where the 7.5 was.
 

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Sean,

Take a look under the car at the the rear diff cover to see if it's marked 7.5 or 8.8 like Michael said. A lot of early 3.8 cars did come with an 8.8 case.

Joe
 

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I could do the gears for you. One thing to find out first is if you have a 7.5 or 8.8 diff, and if you have a TL or not. Odds are, since it is a 3.8NA car, you probably have a 7.5 open diff. You could swap a set of 3.73s into that, but you would have to buy gears for a 7.5" diff, and unless you find a TL unit for a 7.5" IRS diff, you would still have an open diff. Your best bet would be to get an 8.8" diff (maybe even an aluminum housing), a TL unit for an 8.8 IRS, and 3.73 gears for an 8.8. If you look on ebay, you can find stock ford take-out 3.73 gears for an 8.8 on ebay for under $100. You will also need an install kit to get the crush sleeve and depending how the new gears mesh, you might need the shims out of it as well. For a TL unit, if you can find one out of an 89-95 SC, it will have TL rear. Depending on the condition of the clutches in it though, you might want to replace them at the same time. Or you could get a whole new TL unit, but make sure you buy one for IRS, cause otherwise you will assemble everything and the axles will go in, but they will never come out.
 

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Discussion Starter #19
ok car is a 7.5... crawled under and "7.5" is stamped into the back of the diff cover. I have tracked down a 8.8 with trak-loc from a SC picking it up Saturday hopefully.

MadMike... I wouldnt mind taking a drive down to tinton falls if you really can do it. What would i need to bring for you to be able to do this parts wise, besides the 4:10 gears. and how much would you charge to do it for me? I'll send a PM too, Thanks
 

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Discussion Starter #20
ok so i ordered a 4.10 gear kit and already have the 8.8 with trak-loc, but i wanted to know what speedo gear i need. I've heard the purple 21 tooth one is what i need but i just wanted to double check before i buy it
Thanks!
 
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