Gear Swap Info

oneba87lx · 09-09-2002, 12:01 AM

I would like to change rear gears in a friends car. I've never done this before. But it seems like I saw an article somewhere on the net, that said you could change them withouot any special tools. I am a fairly competent shade tree mechanic with a good set of tools. But I don't have many measurement tools. Also all the local shops are qouting him a price of $300-400 just for labor. This seems way to high. For that price we could buy specialty tools, do the work ourselves and probably still save money.

cyberstang5.0 · 09-09-2002, 07:24 AM

Installing a rear end is very hard if you have never done one before. I think you should take it somewhere and have it done. If you don't adjust the backlashing and align the teeth just right, it will start to whine and chew up the teeth.

I had my 3.73 installed professionally. Haven't had a problem since. 300-400 just for labor is pretty expensive, but it's litterally an all day install. I spent about 400-450 (with parts) for mine. Look around at other performance shops. I would also go with a performance shop as opposed to a "normal" shop.

Dark_5.0 · 09-09-2002, 08:47 AM

When I did mine it took me about 5 hours and I had never did a gear swap before.

It was so easy I was embarrassed that I put it off for so long.

BTW: Buy FMS gears and it will go real easy.

Later,

mike72678 · 09-09-2002, 10:14 AM

i have done a couple of rear end jobs setting up new gears in my cars and the only specialty tools you need really are ; a dial indicator to check the lash , and some shutoff ink to check the tooth pattern to make sure they are meshing in the center , when either of these is out you have to adjust it with shims to make it correct . i would agree and make sure you use ford motorsport gears , they are the best . i would also reccomend using synthetic 75-90w oil as it will also quiet it down and get some posi traction additive as this will bring some more life back into your posi .

jimberg · 09-09-2002, 10:29 AM

The reason to use the FMS gears, besides being the best, is that they are machined to be assembled on an assembly line and they don't really have time to go over everything with measurement tools. The shims that are already in place will likely be the correct ones for your new gear. Check your mesh pattern, of course, but it's likely going to be correct.

Changing gears is one of those things that a lot of people believe is more of an art form than mechanical. That's just a perception that people probably get from the difficulty involved with installing third party gears. It's not that hard.

SlowGT · 09-09-2002, 10:36 AM

I put my first set in and they were FMS. They didn't come with any measurements. My current gears are Richmond and they came with the measurements marked right on the pinion.

You might want to rebuild the clutch pak while you're in there. A rebuild kit's only an extra $50.

Also, I've had 3 different shops that specialize in trannies and rearends recommend against synthetic gear oil. They claim that the Ford friction modifier doesn't blend as well with synthetic. I got that answere after I used Mobil 1 and ended up with the posi not acting right. Opened it up and gave it a good carb cleaner bath then filled it back up with Valvoline + friction modifier and it worked fine.

Just my $.02

jimberg · 09-09-2002, 01:13 PM

FMS don't come with measurements since they are all made to be interchangable.

Stang39r · 09-09-2002, 02:16 PM

hey...that rebuild kit. where do you get it from and what does it include (if everything, just say everthing)?? i got my gear and install will be around $150. just tryin to find a total price.

also, got a 95 gt auto and wonderin where to get the best speedo gear and cheapest. thanx

SlowGT · 09-09-2002, 02:31 PM

The Trak-Lok rebuild kit includes the clutches, spacers, shims and 1 bottle of Ford friction modifier.

Mustang_289 · 09-09-2002, 03:16 PM

Over the winter my son and I are going to upgrade to 3.73s, we're also looking at an Eaton differential and 31-spline axles. In addition to the gears, how hard is it to install the Eaton and new axles?

andy669 · 09-09-2002, 03:39 PM

The Richmond gears come stamped with an actual pinion depth number, a number that can be obtained by using a dial type pinion depth gauge.

Ford gears do not come stamped with a pinion depth number. They are designed to be installed by using the Ford pinion depth gauge T79P-4020-A. You basically shim the pinion until it touches this gauge, it has no numbers on it.

Many people have had luck swapping the gears and reusing the stock rearend shims when using FMS parts. This is definatley not the right way to do it though.

A properly set up gearset will have proper pinion depth, preload, and backlash. All of those require special tools and experience to obtain.

Andy

chico · 09-09-2002, 07:37 PM

Slow GT is correct about the synthetic gear oil. Friction modifier will not mix with it....

SlowGT · 09-09-2002, 09:27 PM

Hey Chico:

Are you listed in the users' rides?? Curious to see the combo that's giving you that much HP in a vert.

Disregard. I found your listing. Nice setup

Coupe50h · 09-09-2002, 09:39 PM

Yea my ford racing catalog has a trak loc rebuild kit for like 49$ most shops should throw it in while installing gears since its already opened up(if you buy the rebuild kit), at least thats what im hopeing they will do for me while they install my 373's, after i get my clutch in..

let me know and i'll dig up the part # for that kit.

chico · 09-09-2002, 10:20 PM

For those of you interested... I just had my 3rd motor installed 2,000 miles ago.... the 31 spleen axels, 4.10 gears and Eaton posi is agood comb. it's what I run. Make sure you get the heavy duty Eaton Posi. it puts 800 lbs. torque to ea. wheel compared to 350 stock. Also make sure the ABS gears come with the kit. Agood rear end shop can do the complete swap in 2 hrs. I run 510 rwhp on 91 octane at 7000 rpmsm 417 lbs torque, 14 lbs boost with CP 8.3 comp. pistons, aftclr, stage 2 heads along with a few other goodies. 11. 02 @ 126 mph. Still have 40 more rwhp on tap with a 4 degree advance module..)need Torco Fuel Accelator to ngive you 102 octane to handel the advance) Have not tried the module yet or icing my aftclr box. This is supposed to give me a total of 60 more rwhp. (570) this definately puts me into (with hook up) the mid to upper 10 sec range.

mike72678 · 09-10-2002, 10:35 AM

the depth of the pinion means nothing if the pinion teeth are off , the correct way to check this is to ink up the gears and spin them around and look for the spot in the ink where the gears are meshing , it should be as close to the center of the tooth as possible . what i hear is that on the fms gears the whole tooth will hit when in the center , and on the richmonds , there is usually a high spot on each tooth which means you must get that high spot right in the center of the tooth and then after the gear breks in it will be at full contact on the whole tooth. i have had experience with each of these gears and i found this to be true .

09-09-2002, 12:01 AM	#1
oneba87lx Registered Member Join Date: Jun 2001 Location: lake city, FL Posts: 26	Gear Swap Info I would like to change rear gears in a friends car. I've never done this before. But it seems like I saw an article somewhere on the net, that said you could change them withouot any special tools. I am a fairly competent shade tree mechanic with a good set of tools. But I don't have many measurement tools. Also all the local shops are qouting him a price of $300-400 just for labor. This seems way to high. For that price we could buy specialty tools, do the work ourselves and probably still save money. __________________ 87 notch,maf conv, gt-40 int, gt-40 heads, f303, 1.6rr,24lb inj,190lph, 3 chamber flowmasters, mac equal length shorties,3.73's

09-09-2002, 08:47 AM	#3
Dark_5.0 Registered Member Join Date: Apr 2001 Location: Staging lane Posts: 4,337	When I did mine it took me about 5 hours and I had never did a gear swap before. It was so easy I was embarrassed that I put it off for so long. BTW: Buy FMS gears and it will go real easy. Later, __________________ 92' LX-Big brakes, Lots and lots of suspension, GT40X heads, Ported cobra intake, stock cam, Vortech SC trim. 00' Lightning-Stock 88'CRX-13 second ego killer

09-09-2002, 10:29 AM	#5
jimberg Registered Member Join Date: Oct 1998 Location: Rogers, MN Posts: 2,089	The reason to use the FMS gears, besides being the best, is that they are machined to be assembled on an assembly line and they don't really have time to go over everything with measurement tools. The shims that are already in place will likely be the correct ones for your new gear. Check your mesh pattern, of course, but it's likely going to be correct. Changing gears is one of those things that a lot of people believe is more of an art form than mechanical. That's just a perception that people probably get from the difficulty involved with installing third party gears. It's not that hard. __________________ 351W 89 Mustang GT Convertible

09-09-2002, 10:36 AM	#6
SlowGT Registered Member Join Date: Jun 1999 Location: Columbia Co, PA Posts: 303	I put my first set in and they were FMS. They didn't come with any measurements. My current gears are Richmond and they came with the measurements marked right on the pinion. You might want to rebuild the clutch pak while you're in there. A rebuild kit's only an extra $50. Also, I've had 3 different shops that specialize in trannies and rearends recommend against synthetic gear oil. They claim that the Ford friction modifier doesn't blend as well with synthetic. I got that answere after I used Mobil 1 and ended up with the posi not acting right. Opened it up and gave it a good carb cleaner bath then filled it back up with Valvoline + friction modifier and it worked fine. Just my $.02 __________________ Old Slow GT New Slow GT--> under construction Latest Addition: 95 Cobra R, #73, bone stock, ~6100 miles.

09-09-2002, 01:13 PM	#7
jimberg Registered Member Join Date: Oct 1998 Location: Rogers, MN Posts: 2,089	FMS don't come with measurements since they are all made to be interchangable. __________________ 351W 89 Mustang GT Convertible

09-09-2002, 07:24 AM	#2
cyberstang5.0 347ci of HORSE POWER!!! Join Date: Jul 2001 Location: Houston, TX Posts: 1,416	Installing a rear end is very hard if you have never done one before. I think you should take it somewhere and have it done. If you don't adjust the backlashing and align the teeth just right, it will start to whine and chew up the teeth. I had my 3.73 installed professionally. Haven't had a problem since. 300-400 just for labor is pretty expensive, but it's litterally an all day install. I spent about 400-450 (with parts) for mine. Look around at other performance shops. I would also go with a performance shop as opposed to a "normal" shop.

09-09-2002, 10:14 AM	#4
mike72678 MW Link Sponsor Join Date: Sep 2002 Location: rochester , ny Posts: 79	i have done a couple of rear end jobs setting up new gears in my cars and the only specialty tools you need really are ; a dial indicator to check the lash , and some shutoff ink to check the tooth pattern to make sure they are meshing in the center , when either of these is out you have to adjust it with shims to make it correct . i would agree and make sure you use ford motorsport gears , they are the best . i would also reccomend using synthetic 75-90w oil as it will also quiet it down and get some posi traction additive as this will bring some more life back into your posi .

09-09-2002, 02:16 PM	#8
Stang39r Registered Member Join Date: Feb 2002 Location: Chicago Posts: 53	hey...that rebuild kit. where do you get it from and what does it include (if everything, just say everthing)?? i got my gear and install will be around $150. just tryin to find a total price. also, got a 95 gt auto and wonderin where to get the best speedo gear and cheapest. thanx

09-09-2002, 02:31 PM	#9
SlowGT Registered Member Join Date: Jun 1999 Location: Columbia Co, PA Posts: 303	The Trak-Lok rebuild kit includes the clutches, spacers, shims and 1 bottle of Ford friction modifier. __________________ Old Slow GT New Slow GT--> under construction Latest Addition: 95 Cobra R, #73, bone stock, ~6100 miles.

09-09-2002, 03:16 PM	#10
Mustang_289 Registered Member Join Date: Sep 2001 Posts: 512	Over the winter my son and I are going to upgrade to 3.73s, we're also looking at an Eaton differential and 31-spline axles. In addition to the gears, how hard is it to install the Eaton and new axles?

09-09-2002, 03:39 PM	#11
andy669 Registered Member Join Date: Jan 2001 Location: Moline Il Posts: 901	The Richmond gears come stamped with an actual pinion depth number, a number that can be obtained by using a dial type pinion depth gauge. Ford gears do not come stamped with a pinion depth number. They are designed to be installed by using the Ford pinion depth gauge T79P-4020-A. You basically shim the pinion until it touches this gauge, it has no numbers on it. Many people have had luck swapping the gears and reusing the stock rearend shims when using FMS parts. This is definatley not the right way to do it though. A properly set up gearset will have proper pinion depth, preload, and backlash. All of those require special tools and experience to obtain. Andy __________________ 88 coupe 91 LX NMRA Pure Street 5120

09-09-2002, 07:37 PM	#12
chico Registered Member Join Date: Jul 2002 Location: Manteca,Ca. Posts: 114	rear end gear oil Slow GT is correct about the synthetic gear oil. Friction modifier will not mix with it.... __________________ 98 cobra convt. 515 rwhp 421 torque..554 rwhp on 98 octane..635 rwhp this summer

09-09-2002, 09:27 PM	#13
SlowGT Registered Member Join Date: Jun 1999 Location: Columbia Co, PA Posts: 303	Hey Chico: Are you listed in the users' rides?? Curious to see the combo that's giving you that much HP in a vert. Disregard. I found your listing. Nice setup __________________ Old Slow GT New Slow GT--> under construction Latest Addition: 95 Cobra R, #73, bone stock, ~6100 miles.

09-09-2002, 09:39 PM	#14
Coupe50h Registered Member Join Date: Aug 2002 Location: SanAntonio, Tx Posts: 957	Yea my ford racing catalog has a trak loc rebuild kit for like 49$ most shops should throw it in while installing gears since its already opened up(if you buy the rebuild kit), at least thats what im hopeing they will do for me while they install my 373's, after i get my clutch in.. let me know and i'll dig up the part # for that kit. __________________ X-Texas highway patrol ssp 1990 coupe - exploder Gt-40 iron heads, Explorer intake, 19 lber's. E-cam. crane 1.7 rollers. 190fp. 75mm maf. 65mm tb, tubular subframe connectors, mac cai, Asp crank pulley, T-5, king cobra clutch, flowtech 1-5/8 unequals, mac X-pipe Frpp driveshaft, lakewood Lca's. race weight 3,160 12.69 @ 107.35, 1.71 60' 26x8.5 drag's 3.90 gear 13.20 @ 106.91 - 235/60/15 firestones 2.3 60' 3.27 gear

09-09-2002, 10:20 PM	#15
chico Registered Member Join Date: Jul 2002 Location: Manteca,Ca. Posts: 114	mods/rear end For those of you interested... I just had my 3rd motor installed 2,000 miles ago.... the 31 spleen axels, 4.10 gears and Eaton posi is agood comb. it's what I run. Make sure you get the heavy duty Eaton Posi. it puts 800 lbs. torque to ea. wheel compared to 350 stock. Also make sure the ABS gears come with the kit. Agood rear end shop can do the complete swap in 2 hrs. I run 510 rwhp on 91 octane at 7000 rpmsm 417 lbs torque, 14 lbs boost with CP 8.3 comp. pistons, aftclr, stage 2 heads along with a few other goodies. 11. 02 @ 126 mph. Still have 40 more rwhp on tap with a 4 degree advance module..)need Torco Fuel Accelator to ngive you 102 octane to handel the advance) Have not tried the module yet or icing my aftclr box. This is supposed to give me a total of 60 more rwhp. (570) this definately puts me into (with hook up) the mid to upper 10 sec range. __________________ 98 cobra convt. 515 rwhp 421 torque..554 rwhp on 98 octane..635 rwhp this summer

09-10-2002, 10:35 AM	#16
mike72678 MW Link Sponsor Join Date: Sep 2002 Location: rochester , ny Posts: 79	the depth of the pinion means nothing if the pinion teeth are off , the correct way to check this is to ink up the gears and spin them around and look for the spot in the ink where the gears are meshing , it should be as close to the center of the tooth as possible . what i hear is that on the fms gears the whole tooth will hit when in the center , and on the richmonds , there is usually a high spot on each tooth which means you must get that high spot right in the center of the tooth and then after the gear breks in it will be at full contact on the whole tooth. i have had experience with each of these gears and i found this to be true .

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