Anyone done a 4:11 to 3:73 gear swap

[CruiserCliff]

From what I have heard, my '78 came with 4:11 gears. No reason to believe anything different is in there. Thinking of swapping some 3:73 gears into it. I know I will gain some top end, and lose some low end power, but for a 40 that will not see much if any off road time... I wonder if I will be happy.

Has anyone out there performed this major surgery??? And... are you happy with the results?

CC

 

[John Smith]

For a rig that sees a lot of highway miles and not many trail miles I think it is a good swap. You should have no problem finding someone who wants your highly desirable fine spline diffs to trade with.

 

[Poser]

Do you have a lift?



33" tires are a lot easier to install.....

 

[CruiserCliff]

Do you have a lift?



33" tires are a lot easier to install.....

Not sure... Its on 32 -11.5 - 15's right now. Old Man Emu shocks, but I think stock springs. I dont plan on lifting it.

I will try to post a pic later today.

CC

 

[vtcruiser60]

Here is what I would do....I would buy some cheap 3.73 differentials from say this guy (https://forum.ih8mud.com/sale-parts/204266-buy-my-mothers-third-member-3-73-differentials-sale.html)

Save the containers and put your 4.11's up for sale at the same price, plus the cost of your gaskets and oil.

The job pays for itself.

 

[ken_79-fj40]

I have the stock 3.70 or 3.73 gears in my 79 with 33's. It's nice on the road, but slow going off road is tough. I rarely need it, but an orion for those situations sure would be nice.

 

[Johnnymiz]

i have a 78 that sees very little off road.... unless u consider the brooklyn-queens expressway off roading, i do. i changed out the 4.10 thirds for 3.70's. with 31-10.5 15 tires, 4th gear, exactly 3000 rpm on my autometer tach, i cruise at exactly 70 mph according to my garmin nuvi 680. off the line it's a little slower, but it was never fast, trust me. and if you're not in a hurry, no gas needed, just lift off the clutch and it just walks away without stalling. makes it much nicer to drive it to work from long island.... it's parked a few blocks off wall street right now. can't wait for the drive home

 

[cruiser_guy]

We have 3.7's in the '55 but it also has a turbo'd 3B diesel, H41 low range tranny and the three speed transfer case to help out on the low end. We're also running 33x9.5's.

 

[FJ40-GARAGE]

Just changed over from 3.7 to 4.11, after 31 years...

3.7 was the original setup on the german market to hit the autobahn.
With original tires its a perfect setup with the 3.7 and even up to 33s its no problem. In 1977 my cruiser came with 7.50x16 thats roughly the same as 32s.

Now i got 35s on it for a while and it was time to do something so i changed to the shorter gears.....hell that is a difference now

Get prepared to drive 100mph with yours......but dont get caught.

 

[dieselcruiserhead]

It's not a bad swap at all and nice on the highway with a 4 speed...

 

[Stumpalama]

I have some 3.73's if you need them $50 plus shipping and they're yours.

 

[mano002]

my 78 came with 3.73 gears in it, so you might want to pull the rear diff cover off and check. there is a stamping in the ring gear that is a ratio that'll work out to 3.73 : 1 or 4.1 : 1.

 

[pbgbottle]

thats because you are in canada we got the 3.73 in 78 .

my 78 came with 3.73 gears in it, so you might want to pull the rear diff cover off and check. there is a stamping in the ring gear that is a ratio that'll work out to 3.73 : 1 or 4.1 : 1.

 

[dgangle]

Yes and it is my opinion one of the best mods for me. Better brakes need to be addressed at or before, though. I can keep up with traffic without running +3000 RPM's. 80MPH is something like 2400RPM, IIRC. Not for everyone, especially on a rock-crawling website but many of us don't need and wouldn't use three digit crawl ratios even if we had them. I changed the whole third members...plus they are not so desirable by many=plentiful and cheap.

 

[Landpimp]

my 82 has 3:7's and 33x9.5s I love the combo for my use(which is pretty much just on the road)

 

[thecrazygreek]

I want to do the same thing and run 3.73's as well. But I have older 69 4.11's. Any difference? whats involved with swapping thirds on a 69?

Thanks

**Stumpalama** I will take those thirds if its all I'm gonna need for the swap...