What should be replaced when swapping diff - TCCoA Forums
 
LinkBack Thread Tools
post #1 of 9 (permalink) Old 06-22-2015, 11:26 PM Thread Starter
4th Gear Poster
 
Join Date: May 2014
Location: Illinois
Posts: 214
What should be replaced when swapping diff

Later this week I am having used diff with 3.73 gears installed. I purchased diff mounts from SCP so that's getting done. Anything else besides new fluid? Somebody mentioned the speedo being off when upgrading from stock 3.08 to 3.73....what do I need to replace to fix that (link to the part would be awesome!!!)

Thanks!!!
lurch is offline  
Sponsored Links
Advertisement
 
post #2 of 9 (permalink) Old 06-23-2015, 07:08 AM
Seasoned PostWhore

Super Moderator
 
Join Date: May 2003
Location: Tinton Falls, NJ
Age: 36
Posts: 7,430
Garage
Send a message via AIM to MadMikeyL
For the speedo, you will need a different speedo gear, either a black 23 tooth gear if you have an 8-tooth drive gear, or an orange 20 tooth gear if you have a 7-tooth drive gear. Since the diff is used, I would suggest replacing the axle seals as well while you have it out.

-91 Cougar LS, coming soon, complete overhaul with a 427" Windsor.
-90 XR7 5-speed black on black w/sunroof, MP2, coated rotors, double intercooler, 15%OD, ported heads, comp stage 1 cam, 85mm TB, 90MM LMAF, 80# injectors, and ported big valve heads
-98 Mark VIII LSC, Procharger P600b, TR3650 swap and 3.73s.
-90 SC Automatic rustbucket winter beater
-97 Tbird Sport 4.6 Nice weather daily driver
-"Your buddy Mike is INSANE!" -ClintD's dad
MadMikeyL is online now  
post #3 of 9 (permalink) Old 06-24-2015, 05:41 AM
Seasoned PostWhore
 
miller1995's Avatar
 
Join Date: Nov 2002
Location: Orland Park, IL
Posts: 2,806
Send a message via AIM to miller1995
You are using the Trans you got from me right? It is from a 2000 mustang so you need a speedcal to go to 3.73s.

-Bryan

Pearl 97 LX Sport - Purchased Feb. 09 - 5x4.5 Bolt patern, Cobra Brakes, Voghtland spings, Silver FR500's, 3.73's, MMX drive shaft...more to come
Denim Blue 97 Cougar Sport - Purchased Nov. 14 - 22k miles and now the daily driver, staying stock
Purple 95LX Supercharged 4.6PI Parting Out
Black '11 VW Jetta Sportwagen TDI 6-speed - Fun but efficient
SOLDWhite '03 Crown Vic P71
Pearl 96 Lx - Parted and gone, some parts still available
SOLD2006 Mazdaspeed6
SOLD1998 Escort ZX2
RIPBlue 97 LX - MANY PARTS STILL AVAILABLE
RIP My Black 95 LX 4.6
miller1995 is offline  
Sponsored Links
Advertisement
 
post #4 of 9 (permalink) Old 06-24-2015, 09:24 AM Thread Starter
4th Gear Poster
 
Join Date: May 2014
Location: Illinois
Posts: 214
That's a bummer. I thought I'd only need to change the speedo gear (which appears easy compared to speedcal install).

Where can I pick up a speedcal and are there instructions for installing on our cars. All I've found are instructions for Mustangs.

Ya, I am installing the 2000 Mustang transmission and the 3.73s I picked up from you. I don't need a tune on top of the speedcal for the transmission to shift correctly do I?

Last edited by lurch; 06-24-2015 at 10:07 AM.
lurch is offline  
post #5 of 9 (permalink) Old 06-24-2015, 03:38 PM
Seasoned PostWhore

Super Moderator
 
Join Date: May 2003
Location: Tinton Falls, NJ
Age: 36
Posts: 7,430
Garage
Send a message via AIM to MadMikeyL
Without a tune or a j-mod, you may hit the rev limiter before the trans has a chance to shift at WOT. Basically the computer knows how long it takes to complete the shift, and how fast the car accelerates, so it will command the shift at say 5500rpm to have it actually shift at 6000rpm. If you put steeper gears, it takes less time to accelerate that additional 500rpm, so now your shift that was commanded at 5500 will not happen till maybe 6200rpm. To fix this requires either commanding the shift earlier (tune) or making the shift happen faster (J-mod). As for the speedcal, the Mustang settings should work since our cars work on the same type of signals for the speedo. My only experience with a speedcal was when I put a TR3650 in my MarkVIII. In that case, the 97/98 MarkVIII speedometer reads off the wheel speed sensor, so the speedo was fine, but my speed sensitive steering was going nuts because the VSS signal was reading like 3 times as fast as I was actually going, so at slow speeds in parking lots, my power assist would cut way back. I used the Mustang settings and my speed sensitive steering now works properly, but I have never bothered to check the exact reading vs actual mph on that car, since it doesn't effect the speedo.

-91 Cougar LS, coming soon, complete overhaul with a 427" Windsor.
-90 XR7 5-speed black on black w/sunroof, MP2, coated rotors, double intercooler, 15%OD, ported heads, comp stage 1 cam, 85mm TB, 90MM LMAF, 80# injectors, and ported big valve heads
-98 Mark VIII LSC, Procharger P600b, TR3650 swap and 3.73s.
-90 SC Automatic rustbucket winter beater
-97 Tbird Sport 4.6 Nice weather daily driver
-"Your buddy Mike is INSANE!" -ClintD's dad
MadMikeyL is online now  
post #6 of 9 (permalink) Old 06-24-2015, 05:38 PM
3rd Gear Poster
 
Draetech09's Avatar
 
Join Date: Sep 2009
Location: Anchorage Alaska
Posts: 179
I thought only 2003 and up Mustang automatic transmissions needed the Speedcal?

If you Fail to plan, then you plan to Fail!
I'll forever bleed Ford Blue

Drae
Draetech09 is offline  
post #7 of 9 (permalink) Old 06-24-2015, 06:09 PM
Seasoned Veteran Poster
 
1995 cougar xr7's Avatar
 
Join Date: Dec 2007
Location: Naples, FL.
Age: 45
Posts: 889
You defiantly need a new tune because of the speed limiter. I have 3:73 and a jmodkhku in my cougar. I changed the speedo gear to a purple one. The problem is the speedo gears don't last that long they get chewed up. The other problem you can't drive over 80 mph because of the speed limiter. It's sucks people passing you on the highway and you can't go any faster
1995 cougar xr7 is offline  
post #8 of 9 (permalink) Old 06-24-2015, 09:02 PM Thread Starter
4th Gear Poster
 
Join Date: May 2014
Location: Illinois
Posts: 214
Argh, all the things I had no idea I needed.

So I need a speedcal to correct the speedometer, and I also need a tune (even with the j-mod already done) to take care of the speed limiter and shift points?

Also, is the new transmission going to shift oddly just driving around town or only at WOT?

As far as needing a tune, I heard from an SCT dealer that I can just purchase the SCT X4 and then adjust the gear ratio and remove the speed limiter right on the device. The alternative is buying the SCT 6600 chip and having a shop tune it for me. Which is the better option?

Lastly, the transmission has not yet been installed. Would it be smart of me to get the SpeedCal before hand and get the wiring done to transmission before having the transmission fully installed? If I don't have speedcal done now, is this something I can do myself later without having a lift or dropping the transmission?

Last edited by lurch; 06-25-2015 at 08:36 AM.
lurch is offline  
post #9 of 9 (permalink) Old 06-28-2015, 03:25 PM
Seasoned PostWhore
 
miller1995's Avatar
 
Join Date: Nov 2002
Location: Orland Park, IL
Posts: 2,806
Send a message via AIM to miller1995
The highest ratio you could run without a Speedcal would be 3.27 with a purple gear. Rule of thumb is that you can go two steps down in gear without getting too out of wack with the shift points. You are going from a 3.27 to 3.73, two steps, so a tune isn't necessary but would still be best. As stated, your speed limiter and shift points (at all throttle positions) will be affected.

I've got an older Speedcal here that I would throw in with the drive shaft. You follow the Mustang directions exactly because the wire color and connectors should be the same.

Our cars don't support adjustment of the speedometer from the EEC.

- Bryan

Pearl 97 LX Sport - Purchased Feb. 09 - 5x4.5 Bolt patern, Cobra Brakes, Voghtland spings, Silver FR500's, 3.73's, MMX drive shaft...more to come
Denim Blue 97 Cougar Sport - Purchased Nov. 14 - 22k miles and now the daily driver, staying stock
Purple 95LX Supercharged 4.6PI Parting Out
Black '11 VW Jetta Sportwagen TDI 6-speed - Fun but efficient
SOLDWhite '03 Crown Vic P71
Pearl 96 Lx - Parted and gone, some parts still available
SOLD2006 Mazdaspeed6
SOLD1998 Escort ZX2
RIPBlue 97 LX - MANY PARTS STILL AVAILABLE
RIP My Black 95 LX 4.6
miller1995 is offline  
Reply

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the TCCoA Forums forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:
OR

Log-in











Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page



Posting Rules  
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome