Transfer Case Questions (2 Viewers)

[Sky King]

With a very long list of things to do on my project this is something I have not got around to dealing with yet but I have some questions. First my set up: 1973 FJ with a 350 Chevy with a SM420 truck transmission, first gear being compound low. The transfer case is two speed, 2H and 4H, there is no 4L. I thought that year came with a three speed transfer case? Obviously changes were made to the drive train and it makes me wonder if a PO chose that case because of the compound low first gear or that was the only T case he had at the time. I do have another T case that came with my cruiser so I need to take a close look at both to see what I have. Maybe the 2 speed is a three that is not shifting properly? How do I identify each to tell what it is? Does anyone here run a SM420 with a T case that has 4 low? That seems like it would make it the ultimate crawler but I might not be seeing disadvantages to that configuration. So if someone can help me ID the cases I have and give any other advice on the subject it would be much appreciated.

Edit: I am also including a recent picture that shows the funky homemade shift lever for the the T case, something that I will be changing but it might also be a clue as to what I have.

 

[pb4ugo]

You need to post pics of the tcase. It most likely has 4 low. It could be stuck or something is stopping it from shifting. I run a sbc/420 but use a non stk case. I know folks have used stk 40 cases with the 420.

 

[charliemeyer007]

I think most folks think the normal transfer case 2H, 4H and 4L is a two speed transfer case. My 300 King Quad has a 5 speed tranny (plus reverse) with a 3 speed transfer case and a rear differential lock (2H, 4H, 4L and 4Super Low. A friend has an old F150 with a 3 speed transfer case, I think its a Ranger unit of some sort.

My F150 has the granny low tranny - I just drive it as a 3 speed normally.

Advanced Adapters made all kinds of stuff.

 

[Sky King]

CM OO7, Yes I drive my 73 F250 as a three speed in traffic, compound 1st and 4L work really well when I plow snow with it in the winter. I was thinking that gear reduction could be useful on my LC.

PB4UGO, Any case #'s or differences in linkage or case shape that I should be looking for? I'll see about getting some pictures.

 

[ijonesinsp]

I have a sbc with a 420 and my original “4 speed” transfer case. The “3 speed” and “4 speed” labels were only to indicate what transmission they came behind. They are both one piece cases with 2H and 4H/4L. Pics needed.

 

[ijonesinsp]

Here is a pic of mine.

 

[pb4ugo]

The early 3 speed case has something like 2.3:1 low range. The 4 speed cases are something like 1.99:1. They all sort of look similar. You probably have an adapter mating the 420 to either a 3 or 4 speed case , or it could be something different. This might be helpful.

T-Case Tech

 

[charliemeyer007]

There is an "adapter" that lets you use a Toy 4sp tranny with the 3sp's transfer case - you get about a half gear lower first in low range plus synchro's, Mark's Offroad had them. No change in top gear still 1-1.

 

[Sky King]

Thanks to all of you for your responses, this has been an education for me. The next trip out to the garage I will be looking at the linkage for the shifter. The weird Alice handle in the cab made out of hardware store parts may be an indicator of more buggery below. I also see that the two lever set up is available as a kit, something I may look into if the problem is linkage related.

 

[pb4ugo]

Does your Tcase shifter even shift to the right when trying to go to 4 low? 1st thing I would do is remove the tcase shifter boot and see if the body or tranny hump is stopping it from going the right. Watch the linkages when trying to shift it. Take pics of the adapter between the trans and tcase too.
AA makes an adapter but so did a lot of members on here who had machine shops make up plate adapters. It was a fairly common mod. They would make a bunch of them to reduce the cost of machining and sell them. They were about 3/4" to 1" thick. I think they used the 3 speed tcase because of the spline count.

 

[Sky King]

Does your Tcase shifter even shift to the right when trying to go to 4 low? 1st thing I would do is remove the tcase shifter boot and see if the body or tranny hump is stopping it from going the right. Watch the linkages when trying to shift it. Take pics of the adapter between the trans and tcase too.
AA makes an adapter but so did a lot of members on here who had machine shops make up plate adapters. It was a fairly common mod. They would make a bunch of them to reduce the cost of machining and sell them. They were about 3/4" to 1" thick. I think they used the 3 speed tcase because of the spline count.

It was a clean clothes day and grocery shopping with the wife. Tomorrow I'll be back out in the garage and give it a good going over and see what the linkage looks like, movement, play, etc.

 

[Sky King]

I had a chance to look things over today. I pulled the boot off and found the linkage to be pretty gummed up , several doses of PB Blaster loosened everything up and got things moving again even to the point of the linkage showing 50 years of wear in it's looseness. I was able to index all the positions but did not have a chance to drive it but I really think when I do I will have 4 low now. I'm still tempted to do a two stick conversion on it but that will come down to whether I can do it without having drop the trans / T case. It looks doable with the floor panel removed but I'll want to check with vendor first to make sure.

 

[ijonesinsp]

I had a chance to look things over today. I pulled the boot off and found the linkage to be pretty gummed up , several doses of PB Blaster loosened everything up and got things moving again even to the point of the linkage showing 50 years of wear in it's looseness. I was able to index all the positions but did not have a chance to drive it but I really think when I do I will have 4 low now. I'm still tempted to do a two stick conversion on it but that will come down to whether I can do it without having drop the trans / T case. It looks doable with the floor panel removed but I'll want to check with vendor first to make sure.

You can do it just pulling the tunnel

 

[peesalot]

FWIW there are no 3 spd tcases from Toyota, the front (4wd) engagement has nothing to do with gearing.
Forwad /Backward will shift the front wheel engagement, left and right will shift between high range and low range.

 

[Sky King]

^^^ Technically that is correct and it was a poor choice of words on my part trying to reference the 2H - 4H -4L function of the transfer case. Haynes will probably never give me a job writing shop manuals!

 

[Firemedic831]

The only advantage to a twin stick is you can run in 2 low.

 

[Sky King]

The only advantage to a twin stick is you can run in 2 low.

Two things appeals to me with the twin stick set up, The simplicity of the linkage compared to stock and the cost from what i'm seeing when buying NOS parts. Three if you count my love of the old school look of two T case levers.

 

[Paul_A]

To run in 2-lo all you have to do is remove the sheetmetal shift gate from the t-case.

 

[ijonesinsp]

The only advantage to a twin stick is you can run in 2 low.

More definitive engagement as well. In my opinion, the Toyota design leaves a little to be desired.

 

[archie73]

Twinstick isn’t that hard to fab up, but it’ll take some staring up from the floor and the transmission. Also, the parts from McMaster are cheaper than the kits when I was looking. If done correctly it’ll solve the slip issue. I have a sm465 and there was a threaded hole in the casting that worked a trick- not positive on the sm420.

As noted above- if 2lo is the desired effect, then simply trimming the shift guid plate is super easy.