700R4 tranny swap

lumpy

lumpy

Gear Grinder
Jun 27, 2014
7
Columbus Indiana
First Name
Mike
Willys Model
  1. Pickup
Willys Year:
  1. 1955
I have a 55 willy truck with a 283 in it. I am getting ready to install a 700r4 and 208 transfercase with original axles in front and rear. I plan on changing the rear to a 9 or 8.8 soon as well
M question is do i change the transfer case or leave the original one? and what about the rear cross member? do i need to but one for the tranny I'm getting or will the old one work?
 
Last edited:
Loaded question. Depends on what you plan to use the truck for etc. Many people ditch the stock transfer case for a more modern quiet one.

I kept mine because I like the way they are built and the ability to add overdrive. I added Teralow gears creating a 3.15 to 1 low range gearing.

Without buying a bunch of adapters, you can run a Chevy transfer case. You have overdrive in your 700r4 so now you just have to look at how low of gearing you want in 4x4 low. General rule older cast Iron GM stuff is 2 to 1.(New Process 203 or 205)Aluminum newer cases are 2.72 to 1 ( New Process 208 231 etc). Late 1980's they went to drivers side drop in most GM trucks. K5 Blazers, Burbs and k30 Crew cabs remained square bodies with passenger side drop till 1991. If you are not going to lift, look into clocking a GM case up. They hang down.

If you are going to change rear axle. It will most likely be a centeted pumpkin. Dana 18 is offset rear output. Not a deal breaker just not the ideal situation.

You can adapt to your Dana 18 or a Dana 20 or a Dana 300.

So what I am saying...do some research. Check your wallet, be realistic on how you want to use the rig, then make a choice.

Best of luck

Duane

You can probably use your rear crossmember for a Dana 20 or 18 simply by moving it back

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thanks for the info, I picked up a 700R4 with 208 transfer case with passenger side drop. this is going to be a winter project because i will be changing then rear end as well just have not bought one yet. I will mainly be cruising with my truck prob never see mud lol just want to take on drives with the wife and go to shows and swap meets so i will want to be able to drive on high ways at times
 
Be sure to sell your t90 and Dana 18 and recoup a few pennies. With the pickup rear end being wider, you should have no problem finding a good donor rear diff.

The 700r4/208 combo will be a sweet upgrade. Browse through the builds section in your spare time. I am sure you will find multiple people have done it. Get some ideas on crossmembers and if they had to modify the floor tunnel.

Best of luck,
Duane

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Check out the last pages of "where was your willys today"

I was just there reading and thought of you.

A guy named Larry Messing has a Chevy 350 tbi, 700r4, 208 in a 1950's pickup.

Pick his brain before you start. Maybe he can share pictures of his mounts and such.

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Welderjoe
did it relocate the sticks on the transfer case through the floor? where did the adapter come from connecting the tranny and d18?
 
For a rear axle I would suggest an 8.8 out of a Ford Explorer 1996-2001+. They are 58.xx inches wide so no need to shorten. However the 5 lugs are on 4.5 circle instead of 5.5. You can have them re drilled or use an adapter. Pre 96 are drum brake. The pumpkin is slightly off center to the pass side, so would likely work with the D18. Lots of them in junk yards, lots of good ratios available, and tons of aftermarket support.
 
Hey Mike ...Ok here are a few pics of my 700R4 and NP208 during preparation for installation in my 51 truck IMG_2293.jpgIMG_2294.jpg IMG_2296.jpg this shows the custom trans mount cross member i made to support the tranny IMG_2493.jpgIMG_2494.jpghere are couple pics showing whole mess installed in my truck IMG_2303.jpg IMG_3010.jpgIMG_3012.jpgIMG_3013.jpg

you may have to cut the firewall and remove the front part of existing tunnel and make it bigger to accomadate the 700R4 bellhousing IMG_3064.jpg depending on how big and where your engine sits. My truck has a 95 chevy 5.7 350 TBI in it that was just laying in engine bay not bolted to anything when i bought it giving me the freedom to put it exactly where it needed to be in order for everything else to work. I could not just bolt it in and call it good this took time..... forward, backward, left,right, higher, lower ...what bout radiator? how bout fans?.....rear distributor clearance? pulley to radiator clearance? hood closing height?....once all these variables were worked out then i made custom engine mounts after mocking them up out of foam core. though i wish i had extra inch or so clearance in rear at distributor .but it worked out pretty good none the less. truck now runs and drives ....will see how long that lasts.

any questions feel free to ask will try to answer within my limited knowledge abilty.


Larry
 
Hey lumpy I have a wagon with a 283 in it and a 700r4 yes that's had to
relocate the twin sticks I have a advance adapter mating the two, I made the cross member and have 356 gears the fastest I have had it up to was 85mph but it was kinda scary with the steering lol.. I have the single wire over drive I run 65-70mph with no problems all day hope this helps sorry for the late reply
Ray
 
Larry Messing said:
Hey Mike ...Ok here are a few pics of my 700R4 and NP208 during preparation for installation in my 51 truck View attachment 38683View attachment 38684 View attachment 38685 this shows the custom trans mount cross member i made to support the tranny View attachment 38686View attachment 38687here are couple pics showing whole mess installed in my truck View attachment 38691 View attachment 38688View attachment 38689View attachment 38690

you may have to cut the firewall and remove the front part of existing tunnel and make it bigger to accomadate the 700R4 bellhousing View attachment 38692 depending on how big and where your engine sits. My truck has a 95 chevy 5.7 350 TBI in it that was just laying in engine bay not bolted to anything when i bought it giving me the freedom to put it exactly where it needed to be in order for everything else to work. I could not just bolt it in and call it good this took time..... forward, backward, left,right, higher, lower ...what bout radiator? how bout fans?.....rear distributor clearance? pulley to radiator clearance? hood closing height?....once all these variables were worked out then i made custom engine mounts after mocking them up out of foam core. though i wish i had extra inch or so clearance in rear at distributor .but it worked out pretty good none the less. truck now runs and drives ....will see how long that lasts.

any questions feel free to ask will try to answer within my limited knowledge abilty.


Larry
Click to expand...


Thank you so much for the pics, they help. I just lost 1& 2 gear in my original tranny so the 700 is going in sooner then i had planned and the 9 inch as well while it is down might as well do it all, right? thanks again
 
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