81 Capri help needed

[1981Capri]

Hi Everyone, Thanks for taking a look and any help you can give.

1981 Mercury Capri RS 6 Cyl, 3.3L 200

Needs rear end cover & gasket. What size is the rear end and what type and quantity of rear end fluid do I need?

Car has a 4 speed manual transmission. I want to change the transmission fluid. What type and quantity of transmission fluid do I need?

[Chris Wood]

Rear should be a 7.5". It should take about two quarts, I personally like royal purple's line of products, RP's MaxGear 75w-90; and for the limited slip application--it already has the friction modifier in it.

As for the transmission, it should take about 3 quarts if I remember correctly, and for that I like the RP Synchromax.

Oriley's carries the RP line.

[wraithracing]

Chris may be correct above, but my information shows that you might have the 6.75 rear end instead of the 7.5. The door tag should help determine which you have.

Also on the SROD, IIRC they used 70/80w gear oil instead of the Dexron II or Mercon.

I could be wrong, but I remember all of the SROD's I have removed had gear oil in them. Now where or not that was correct. . .

Trey

[arj]

It might be smaller than 7.5. The white Black Magic owned by 'terrymwalsh' is an '81 with the 3.3, and it came with the 6.75 rear end.

[TWR2003]

Car has a 4 speed manual transmission.

Is that trans a true 4 speed or the SROD 3 + OD?

Thanks
T

[nuckinfutzracing]

Is that trans a true 4 speed or the SROD 3 + OD?

Thanks
T

It might be the T-10 or the super T-10 IIRC. Please correct me if im wrong because id like to know to for curiosity sake .

[wraithracing]

All the information I have shows the transmission should be a SROD. Which is a 4 speed transmission or as some call it a 3 + OD. Again, all of this is just based upon the different books and manuals that I have. I have no door tag, transmission tag, or rear end tag information to go by either.

I am sure Fox Chassis has better information than I do, maybe he can post up better information.

Trey

[FoxChassis]

There was a 6.75" rear from '79 through '82. Not sure which powertrains got that 6.75" rear but the 2.3T and the V8 got the 7.5" rear. The door tag won't tell you the ring gear size, it will only tell you the gear ratio. The axle tag will tell you the ring gear size. The code will be "6 7" for the 6.75" rear and "7 5" for the 7.5" rear. I made an axle tag decoder here.

There were three different 4-sp transmissions in '81, at least according to the book I have. At least one of them (the SROD, code 4 on the door tag) had overdrive (3+1). Not sure about the other two (code 6 Borg Warner, and code 7 Hummer). I have only ever seen the code 4 trans as the manual behind the 3.3L in '81. But that is just from the door tag data that I have collected. The auto trans behind the 3.3L has only ever been a C4 (code W), again just from the data I have collected. I have seen the code 7 trans behind the 2.3L (non-turbo). I have not ever seen an '81 door tag with a code 6 trans. The last year I saw that code 6 trans on door tags was '80, and only behind the 2.3L and 2.3T.

There was also a 5-sp w/ OD but that was only behind the 4-cyl (turbo or non-turbo).

[wraithracing]

Thanks FoxChassis!

That information matches what I have in my books. Depending on the gear ratio the OP has, it might be able to determine the rear axle. I have a list of different ratios available so that might work. Otherwise as stated above you will just need to get the tag information off the rear axle.

Trey

[FoxChassis]

Being a 3.3L with 4-sp OD, there were two ratios available:

3.08:1 (50-state)
2.47:1 (49-state)

Both were available with or without Traction-Lok.

[FoxChassis]

I take back what I said about not seeing a code 6 trans in '81. I did not check the Capri door tags, I only checked the Mustang door tags. There are a couple '81 Capris in the dtabase with a 3.3L and a code 6 4-sp.

Also forget the above post about 3.08 or 2.47 being the only two ratios. I should remember to always check the actual data against what the books and factory literature says, before I say something wasn't available.

Here is the data that I have collected so far for of the combos of axle ratios/transmissions behind the 3.3L (Capri and Mustang):

8/W
B/6
M/W
Y/4

8 = 2.73:1 non-locking
B = 2.47:1 non-locking
M = 2.73:1 locking
Y = 3.08:1 non-locking

4 = 4-sp manual SROD (Tremec)
6 = 4-sp manual (Borg Warner)
W = 3-sp auto C4

[1981Capri]

Ok Great thanks for all your help.

[1981Capri]

Thanks again for your help. We want to keep the original motor but we want to make it go faster. What do you recommend to tweak it up and make it go faster?

[KJDad]

Being a 3.3L with 4-sp OD, there were two ratios available:

3.08:1 (50-state)
2.47:1 (49-state)

Both were available with or without Traction-Lok.

I can even imagine how slow a 3.3 with a 2.47 would be...

[1981Capri]

That's why we want to make it go faster

[Chrome_Rush]

Well if you do.t want to change the engine. Swapping to a better gear in the rear end will help a ton. I'm not sure about a 6.75 but I know if you swap in a 7.5 or an8.8 you can get basically any gear ration you want.

[chargedGT]

If you are going to keep the engine, switching to a 7.5 would probably be your best option, it is little bit lighter than the 8.8 and will be plenty strong.

[wraithracing]

As stated above the 7.5 will work just fine with your 3.3L. There are plenty of ratios available that will work just fine for you. Depending on your area you might be able to find someone upgrading from a 7.5 to an 8.8 and you can get the 7.5 for next to nothing. Check out craigslist, etc. and I am sure you will find something. Essentially all your V8 and turbo Foxes up until 85 had the 7.5. After that only the 4cyl Aero cars had the 7.5.

Of course, T-birds/Cougars are another option, but you may have to deal with different track widths depending on the year model and brakes.

Good Luck!

Trey

[Jimbo302]

I was perusing older threads and I wanted to post and say thanks for the great info in this thread.

Also for the sake of info, my 1981 Zephyr wagon with the 255 V8 has a 7.5 rear and 2.26 gearing, I believe.

[xctasy]

My '81 Mustang has the lovely weak kneed ex Pinto and Mustang II 6.75".

Lots of the San Jose high mount blue engines 3.3's often do. I think 2.73 was the only Fox I6 6.75 ratio, but some 3.08's and 3.45's were 6.75's too. Some 3.08's and all 2.47 were 7.5" diff ratios. The same as the ranger Code 72 3.08 and Code 74 3.45's

The repudedly 205 lb-ft limit C3 automatic was a feature, and some bellhousings for that year were certainly Code 6 trans capable, that is the non 5-speed, non T5, Borg Warner T4 4-speed non overdrive.

The in line sixes weren't going to hurt any kind of SROD, Borg Warner T4 or C3 Bourdeux auto in a hurry. The limited slip diff was a new option in 1981 after two years of axle tramping turbos and V8's, it was hard to see how a 90 odd horse[pwer engine could injure a 24 spline 6.75"diff, but if its got a limited slip diff its 7.5"