What is your opinion? 3.80 or 4.10 8" rear

bryanvw61 · Jun 10, 2008

I just finished converting a 6cyl automatic coupe to a v8 with a t5. The 2.80 rear is going to have to go. the t5 is a close ratio ford motorsports unit with a .68 OD. The car is built to be a street machine, with some occasional strip, hence the comp cams xe268h. I look at the gear calculators and form some opinions, but I want to know what people that have it think. Thanks!

Tires are 225/50/16 for those that care

chromedog · Jun 10, 2008

ive got 3.50 gears behind my aod, and the car is plenty quick out of the hole, yet still only turns 2200 rpm at 75 mph.

BornInAFord · Jun 10, 2008

Go with a 3.80 or even a 3.55. Otherwise you just installed an expensive 4 speed... I'm happy with my 3.40:1 rear and 2.95 first, and even then I have to shift quickly. You have a 3.35 first, which is even lower geared. Your 0.68 overdrive should work nicely on the highway with either the 3.55 or 3.80 and your cam. :thumbup:

Daniel

jamison42166 · Jun 10, 2008

I went with a 3.80 8" LSD on my mustang so it would work better with the Edelbrock RPM power package on the car. the car is snappy off the line but with a C4 im running 3500 RPMS at 55 MPH with 3 gears and no overdrive its a bit much. After rebuilding the tranny if i had to do it over ida converted it to a 5 speed.
im probably going to add a Gear vendors OD at some point although ill have to lose my Xframe assembly or notch the hell out of it.
4.10's would be like driving a dump truck, you would be having to shift too soon and wouldnt take advantage of your engines torque curve.

bryanvw61 · Jun 11, 2008

actually i do have a 2.95 first, 1.94, 1.34, 1, and my OD is .63 sorry for the typo

not sure if this changes any opinions or not

BornInAFord · Jun 11, 2008

If that's the case, either 3.80 or 4.11 would work great. My 3.40 is good off the line, but the 55MPH suggested speed limit here keeps the engine chugging along at ~1600, good for economy with my cam, but not for performance at that RPM. A 3.80 rear would give you 6.8MPH/1000RPM in first and 31.7MPH/1000RPM in 5th. A 4.11 rear would give you 6.3 and 29.3, respectively. Either would work depending on what your projected 1/4 mile speed and max desired RPM would be. At 5500RPM in 4th at the end of the quarter, the speed would be ~110MPH for the 3.80 and ~102 for the 4.11. Tough decision, eh?

bryanvw61 · Jun 11, 2008

BornInAFord said:
If that's the case, either 3.80 or 4.11 would work great. My 3.40 is good off the line, but the 55MPH suggested speed limit here keeps the engine chugging along at ~1600, good for economy with my cam, but not for performance at that RPM. A 3.80 rear would give you 6.8MPH/1000RPM in first and 31.7MPH/1000RPM in 5th. A 4.11 rear would give you 6.3 and 29.3, respectively. Either would work depending on what your projected 1/4 mile speed and max desired RPM would be. At 5500RPM in 4th at the end of the quarter, the speed would be ~110MPH for the 3.80 and ~102 for the 4.11. Tough decision, eh?

tough decision... exactly! I know would like to be in the 12s

jcode68 · Jun 11, 2008

I just upgraded from a 2.79 open diff to a 3.80 Traction Loc. Perfect ratio for my T5 and no more 1 wheel peel!
Posted via Mobile Device

edgars23 · Jun 11, 2008

I've got 3.80's in my 9" with a ford trac-lok differential (sp?) and I love the feeling. Perfect off the line and whenever it is gunned, yet not overkill when coasting on the hey.
-Edgar

bryanvw61 · Jun 12, 2008

thanks for the opinions so far! anyone else?

Fast63 · Jun 12, 2008

3.80's for sure is my vote. With 4.10's you will hate first gear.

ForceFed70 · Jun 12, 2008

I have 3.73's and I've been thinking of swapping back to some lower (numerically speaking) gears. I find 1st gear to be pretty much useless... Shifting to 2nd in the middle of a left hand turn is a PITA.

So my vote is for something closer to the 3.50 gear ratio, but engine combo can come into play here. My car makes pretty good power down low (full boost by 2400RPM), so I don't find much of a need to wind it out anyway.

TOM B · Jun 14, 2008

No matter what ratio you decide on, You Must build up that 8 inch so it holds up or CABOOM!
I have a 8 inch in my stang but installed a Lock Right differential from Powertrax, its a posi unit without the clutches and makes the rear stronger. also buy the hardened axles as these break first because there only 28 spine.

ga289stocker · Jun 14, 2008

I have a 3.80 trak look in my 65 w/ a top loader 4sp now. I run 25" diameter
17" tires and turn about 3k rpm @60, not fun. I have under my work bench A 1993 T5 w/ the 3.35 first gear ratio. I thought about getting the 4.10 but it was just to quick of a 1st gear once i make the swap. I'm glad I got the 3.80. My car picked up about 2/10's w/ the gear over the 3.55 wonder wheel i swaped out.
With your 2.95 1st ratio T-5 you should be in great shape.

bryanvw61 · Jun 14, 2008

3.80 looks to be winning by a long shot :SNSign:

57fairlane · Jun 15, 2008

another one for 3.80s . . .

I have 3.55s and a t5 and I wish I had done 3.80s . . . at the time I had a c4 so I was limited on the freeway but now with overdrive: don't fear the gear.

ultrastang · Jun 16, 2008

http://ultrastang.com/Page.asp?PageID=8

68RCodeConv · Jun 19, 2008

Depends on the motor. If it really likes to rev and makes most of its power above 3000 rpm then I would go with 4.11. If it is done at 5500 then go with the 3.75.

My 347 revs freely to 6500 and I have had both 3.89 and 4.11 gears in it. Personally I did not consider the 4.11 to be too much but it is a tad bit easier to launch the car without wheelspin with the 3.89.

iskwezm · Jun 19, 2008

I have 3.80 but want to go to a 3.25.Im not not able to build boost in 1st with it winding out too fast.

ratio411 · Jun 19, 2008

bryanvw61 said:
What is your opinion? 3.80 or 4.10 8" rear

Well, first let's call the gears what they really are... 4.11s are 8" gears.
There is no 4.10 for 8" rears.
It wouldn't be a big deal, except ratio411 doesn't exist if folks call them 4.10s!

I would go 3.80, max.
The cam is smallish for even that much gear.
I know you probably already have the tranny, but wide ratios are generally much more street
friendly. You can make the gear spread feel a little better by using a higher gear (lower numbers).

Edit:

After looking at your first gear... 3.35 from what I read...
I vote 3.55!
That gives you a final drive of 11.89 in first gear.
That is wicked cool. The 3.80 gives you 12.73, which is a bit
much unless you have a really stout cam.

A wide ratio Toploader* with 4.11 gears has a 1st gear final drive of around 11.42...
That is an awesome place to be with a nice street setup.

*The wide ratio Toploader is the $h!t in a street machine...
at least until high fuel prices and strong OD trannys.
The closer you can replicate the gearing of this tranny,
and still have OD, the better off you are IMHO.

What is your opinion? 3.80 or 4.10 8" rear

bryanvw61

New Member

chromedog

New Member

BornInAFord

Member

jamison42166

Member

bryanvw61

New Member

BornInAFord

Member

bryanvw61

New Member

jcode68

Active Member

edgars23

Member

bryanvw61

New Member

Fast63

New Member

ForceFed70

That's why they call it "dope"

TOM B

ga289stocker

Member

bryanvw61

New Member

57fairlane

New Member

ultrastang

68RCodeConv

New Member

iskwezm

ratio411

Similar threads

What is your opinion? 3.80 or 4.10 8" rear

New Member

New Member

Member

Member

New Member

Member

New Member

Active Member

Member

New Member

New Member

That's why they call it "dope"

Member

New Member

New Member

New Member

Similar threads

Privacy & Transparency

Privacy & Transparency