3 spd on the 4spd on the v8

Joined
Jun 14, 2006
Messages
42
Location
Santa Barbara
I found a three speed transfer, 3 spd tranny, both floor shift with a v8 bellhousing for really cheap. Currently I have the stock 1976 4 spd versions of these with the stock 2F. My motor needs work, but tranny is fne, so I was thinking that I might just throw in a V8. I know this will cost a littler more in the end but would be worth it for me. Plus with this setup, I could easily bring the truck back to stock if i wanted in the future.
Questions:
1.) I have read that this 3 spd transfer has a lower range and is desirable over my 4 spd transfer?

2.) Could I retain my 4 spd tranny and still bolt up to both the bellhousing and old 3 spd transfer if a better setup? Even if the v8 didnt work, could i still use the tranfer case to get a lower range?

3.) Other than motor mounts, would a v8 bolt right in without new crossmembers or clutch etc. I have already read about other requirments such as larger radiator.

Thanks for the help!!!!
 

JJS

Joined
Nov 1, 2005
Messages
2,329
Location
USA
You will need to swap the input gear on the 3-spd case to accept the 16-spline 4-spd output. The 3-spd has a better low-range. It's around 2.25:1 as opposed to 1.99:1 from the 4-spd case. I'm not sure if the 3-spd bellhousing adapter is interchangeable with a 4-spd.
 
Joined
May 14, 2006
Messages
1,660
Location
MD 'Burbs of DC
The 3-spd has a better low-range. It's around 2.25:1 as opposed to 1.99:1 from the 4-spd case.

Is this really true? The top gear ratio is the same for the 3- and 4-speed, so what was the advantage of Toyota going to a 4-speed? Sorry if this is a dumb question.
 

splitshot

Head cook, Bottle washer, and Peace keeper.
SILVER Star
Joined
Nov 17, 2006
Messages
7,696
Location
Rodent Central, Az
Is this really true? The top gear ratio is the same for the 3- and 4-speed, so what was the advantage of Toyota going to a 4-speed? Sorry if this is a dumb question.
The 4-speed has much beefier gears..
You can make up the difference just w/ tire size.
 

JJS

Joined
Nov 1, 2005
Messages
2,329
Location
USA
Is this really true? The top gear ratio is the same for the 3- and 4-speed, so what was the advantage of Toyota going to a 4-speed? Sorry if this is a dumb question.

That's why people swap them. I've heard the 3-spd case is more brittle, though.

If you're asking about the tranny, there's a pretty significant 1st gear improvement between the 3 and 4 speed. An H42 first gear is something like 3.5:1. It's no granny 4-spd. The 3-spd has a pretty high first gear. Someone will know it.
 
Joined
Feb 6, 2002
Messages
15,301
Location
OC, CA
There is a lot of info on engine and transmission swaps in tech links. Just click the link at the top of the page.

The low range of the 3sp case is not much lower than the 4sp. It is not worth the effort of swapping a 3sp case for a good 4sp case IMHO.
 

splitshot

Head cook, Bottle washer, and Peace keeper.
SILVER Star
Joined
Nov 17, 2006
Messages
7,696
Location
Rodent Central, Az
And you will have thicker gears to handle a v-8.. But if it were me, I'd stick with your 2-F..
 
Joined
Jun 14, 2006
Messages
42
Location
Santa Barbara
it would not really be a headache, since I have to pull the motor and everything anyway. I was going to go through the tranny and transfer case and replace a few leaking seals...

if anyone has any insight on the bellhousing mating up to my 4 speed which I would be retaining let me know. I would be able to do minor machining if neccesary to make this work
 

Poser

Oh...Durka Durka Durka.
Supporting Vendor
Joined
Oct 1, 2003
Messages
20,456
Location
MN
if anyone has any insight on the bellhousing mating up to my 4 speed which I would be retaining let me know. I would be able to do minor machining if neccesary to make this work



It is beyond 'minor machining'....



You will need to get a four speed V8 flywheel housing, as the Toyota three speed and four speed use different flywheel housings behind the stock 6.


Good luck!


-Steve
 
Joined
Dec 17, 2005
Messages
3,043
The biggest problem with a V-8 conversion using the original transmission and transfer is that the back of the V-8 will hit the firewall unless the whole assembly is moved forward.

This is why the Mark's of Australia kit used an auxilliary bellhousing that fit between the original Toyota bellhousing and the SBC. It spaced the SBC forward, but left the transmission and transfer case in their original positions. The exact thickness of the adaptor is 4.807". The stock Toyota bellhousing is 7.5" thick. Adding them up, the back of the SBC needs to be about 11.5" (11.587" to be exact) forward of the face of the transmission mounting face.

It's possible to move the SBC back a little bit, but, the rear of the right valve cover will run interference with the hose couplings for the heater system in the firewall before the engine fouls the firewall itself. You can see the photo below the tip of the valve cover approaching the heater couplings.

FL000015a.jpg


This photo shows the Toyota bellhousing (black), the Mark's of Australia adaptor (silver) and the SBC (blue). This illustrates the spacing problem with the original transmission location and the SBC. Notice the transmission mount. If the transmission is moved forward, the mounts will have to be relocated or some sort of offset adaptor will have to be made.

FL000013.jpg


This view shows the HEI on the SBC. Note where the original Toyota bellhousing meets the Mark's adaptor. The original bellhousing is slightly recessed under the firewall lip.

FL000008.jpg


This is why the for those using the original transmission and transfer and a SBC that the Mark's kit is a good option (though expensive). The kit is designed for a 4-speed, but it will work with a 3-speed with modifications.

So, my advice is, if you want to retain the stock Toyota drivetrain and go SBC, spend the money on the Mark's kit.

If you don't want to buy the Mark's kit, install more modern running gear and use a combination that will space your SBC far enough forward to clear the firewall and its associated parts. A short automatic would help space the SBC forward, for example.
 

Users who are viewing this thread

Top Bottom