What kind of 4 speed tranny to use?

[AlexB]

i have a 73' 40 got the original 3 speed tranny ans a 3 speed transfer case bolted to original F engine my question was what kind of a 4 speed tranny can i use ( i wanna keep the original 1F in there an the original 3 speed transfer case) and are any out there a direct bolt on? which would u guys suggest?

rookie here sorry for a dumb question just looking for benefits that a 4 speed tranny offers.

Thank you guys soo much ahead

IH8MUD is the S**T !!!!!

 

[John Smith]

i have a 73' 40 got the original 3 speed tranny ans a 3 speed transfer case bolted to original F engine my question was what kind of a 4 speed tranny can i use ( i wanna keep the original 1F in there an the original 3 speed transfer case) and are any out there a direct bolt on? which would u guys suggest?

rookie here sorry for a dumb question just looking for benefits that a 4 speed tranny offers.

Thank you guys soo much ahead

IH8MUD is the S**T !!!!!

The main reason most swap out the stock 3 speed transmission for a 4 speed is because the 4 speed is synchronized, unlike the 3 speed.

 

[AlexB]

explain synchronized please?

thanks

 

[Poser]

explain synchronized please?

thanks

There is not a 'bolt in' four speed transmission, period. There are many pieces other than the four speed transmission that will need to be sourced.


Flywheel housing, drive shafts, adapter/changeover gear and bearing to make the three speed transmission work on the rear of the four speed just for starters. Yes these pieces will ‘bolt up’, but it is not just a matter of removing the three speed and installing the four speed.


FYI- you gain nothing on the top end, as both transmissions are 1:1 in top gear.



Google "synchronized transmission" and read away...






.

 

[Degnol]

YouTube - "Synchronized" Swimming

Kinda like that, but with a transmission


Real answer.....you can shift into 1st without coming to a complete stop or double clutching/matching rpms

 

[Vicm]

Have ever driven a manual trans and you were able to shift from first gear up or down without depressing the clutch?
I can do that with my 4sp fj40 and my 5sp VW Golf.

 

[AlexB]

Hahaha synchronized swimming funny lol

But yeah I drive a 5 speed vr6 gti and after I asked my dad who drove a whole bunch of old school russian military trucks when we still lived in ukraine he explained the difference between synchronized and not synchronized trannys and by the way thank u guys for a quick reply another question I have is. I can only do around 45 to 50 mph on the 3 speed will my speed improve to let's sayyy 65 with a 4 speed?

Thank u guys again

 

[rusty_tlc]

There is not a 'bolt in' four speed transmission, period. There are many pieces other than the four speed transmission that will need to be sourced.


Flywheel housing, drive shafts, adapter/changeover gear and bearing to make the three speed transmission work on the rear of the four speed just for starters. Yes these pieces will ‘bolt up’, but it is not just a matter of removing the three speed and installing the four speed.


FYI- you gain nothing on the top end, as both transmissions are 1:1 in top gear.



Google "synchronized transmission" and read away...






.

What is the low range ratio for the 3spd t-case?

 

[FF LC FREAK]

Hahaha synchronized swimming funny lol

I can only do around 45 to 50 mph on the 3 speed will my speed improve to let's sayyy 65 with a 4 speed?

Thank u guys again

No. Both the 3 speed transmissions and 4 speed transmissions are 1:1 gear ratios in the top gear. If you can't get above 45 to 50, then you have something else going on.

 

[Vicm]

This is all detailed in the Faq ,
T-case Low ratio
3sp 2.31
4sp 1.99

 

[Poser]

This is all detailed in the Faq

Who reads that?

Why would anyone look there?











.

 

[cruiser_guy]

If you are solely after increased speed you can do a "rubber overdrive" (bigger tires), or change out the ring and pinion (both front and rear please) to a 3.7 ratio instead of the stock 4.11 ratio.

It's not too difficult to bolt in the 4 speed in place of the three speed, it just takes sourcing all the parts. Both my '55 and '45LV have a 4 speed and the older 3 speed transfer case.

 

[Downey]

Poser is right, you'll need a 4 speed bellhousing, a 4 spd to 3 spd adapter like the one shown below, plus some driveshaft/flange modifications.

 

[rusty_tlc]

Who reads that?

Why would anyone look there?











.

I actually looked before I ask the question. I just didn't find.

It looks like all the benefit of the 4spd conversion would be on the trail.

Stock 3spd in 1st gear low range
2.72 X 2.31= 6.28

4sp with a 3 spd t-case in first gear low range
3.55X 2.31 = 8.20

 

[rusty_tlc]

Wouldn't it be easier to find a 4sp t-case and put the 3sp gears in it than do all the adapters?

 

[Poser]

Wouldn't it be easier to find a 4sp t-case and put the 3sp gears in it than do all the adapters?

What are you talking about?


There is the input gear, a different output shaft bearing and the sleeve/spacer for the rear of the output shaft.

The input seal and gaskets are just part of the game.


"All the adapters?"


What do you mean?



Further, there is NO WAY I would waste the time and money to replace a three-speed transmission with an H42 and three-speed case under the guise of improved off road performance.

Final drive difference is less than 10.

28:1 VS. 34:1 or around there. In any case, it is not worth the effort and expense if your end result is really trying to get better off road gearing.



Swapping the gears between the case will still require that you get the different input gear. The spline count, three-speed(10) and four-speed to 07/80(16) are not the same...

 

[cruiser_guy]

Stock 3spd in 1st gear low range
2.72 X 2.31= 6.28

4sp with a 3 spd t-case in first gear low range
3.55X 2.31 = 8.20

Don't forget the rest of the ratios

4sp with 4 spd t-case in first gear low range
3.55 x 1.99 = 7.06

H41 4sp with 4 spd t-case in first gear low range
4.9 x 1.99 = 9.75

H41 4sp with 3 spd t-case in first gear low range
4.9 x 2.31 = 11.3

So if you want to go all the way you need the H41 and the 3 speed case.


Jim, don't forget the shifter differences between the three speed and 4 speed transfer cases. You need to locate all the shifter bits as well.

 

[rusty_tlc]

What are you talking about?


There is the input gear, a different output shaft bearing and the sleeve/spacer for the rear of the output shaft.

The input seal and gaskets are just part of the game.


"All the adapters?"


What do you mean?



Further, there is NO WAY I would waste the time and money to replace a three-speed transmission with an H42 and three-speed case under the guise of improved off road performance.

Final drive difference is less than 10.

28:1 VS. 34:1 or around there. In any case, it is not worth the effort and expense if your end result is really trying to get better off road gearing.



Swapping the gears between the case will still require that you get the different input gear. The spline count, three-speed(10) and four-speed to 07/80(16) are not the same...

I thinking about taking a complete 4 spd transmission and t-case and just swapping the gears from the 3 spd t-case in. I didn't know about the 10 spline vs 16 spline issue. I also did not consider that the bell housing would still need to be replaced.

 

[cruiser_guy]

I thinking about taking a complete 4 spd transmission and t-case and just swapping the gears from the 3 spd t-case in. I didn't know about the 10 spline vs 16 spline issue. I also did not consider that the bell housing would still need to be replaced.

You'd be better off swapping in the entire case and then using the shifters and that from the 4 speed case. You'll have a tough time getting the right clearances on the four speed case with three speed gears installed, especially on the idler gear.

 

[too tall]

SM420