Topic: swapping L43 to R151F (or W56 etc)

[scheefdog]

I have a 79 with the original L43 4 speed in it behind a recently rebuilt 20/22r hybrid. I am running Old Man Emu springs with the stock hangers and 5" shackles with stock driveshafts. I just picked up a used R151 turbo tranny that is complete with bellhousing, transfer case, and shifters. I would like to put the tranny in as is(and put 4.7 gears in the transfer case at some point). I have been searching a bunch about swapping to the newer 5 speed and am hoping for a little more info.

1-Tunnel clearance? I have read about the having to pound out the transmission tunnel to make the newer tranny fit. Does anyone have a pic of doing this and exactly where I need to create more room? My R151 is forward shift so the shifters should stick up in about the same location correct? I'm fine with doing some trimming, just wanted to check.

2-Crossmember? I have read that you can just spin the existing crossmember around and the 2 existing rear bolt holes line up so you just have to tap 2 new holes. Once again, anyone have any pics? I would like to eventually switch to a budbuilt crossmember but if it is easy to use the stock one for now I'll do that.  

3-Clutch? I have also read that I have to run a newer clutch master cylinder and slave cylinder. Should I just get the entire clutch assembly off a newer truck? Or can I just add a slave cylinder and use my existing master and line? The R151 has the clutch fork on it. Also, my clutch and flywheel are still in good shape. Can I use them or do I need to get a different clutch?

4-Driveshafts? I know the transmission is 4" longer. Will a front d.s. out of a 84-85 (or a clearenced IFS d.s.) be the correct length? Does anyone know what this length is? With the same thought, I think a 84-88 rear d.s. from a 4runner or SB will fit. Again, do you know the length? (seems like people have driveshafts sitting around but they don't exactly know what they are out of so some measurements would help when I am looking) I don't want to have my existing d.s. modified because the front spline has a lot of play and I would have to ship them somewhere to have it done.

That is a lot of questions, but I know there are at least a few people on here who have done this exact same swap(or a W56).

[scheefdog [OP]]

Anyone?

Here is my thought on the driveshafts;
-currently my front d.s. is about 19.5" fully collapsed and the rear is about 48"

I'm pretty sure a 84-85 front d.s is 25" collapsed and a 84+ rear d.s. is 44" (can anyone verify this, as it helps me while searching for new ones, there are no junk yards close to me so I stuck with the internet to gather parts....)

[hiluxtrux]

Ya, these are the exact questions that keep me from pulling the trigger on one of the longer transmissions for my '80.  I searched for existing threads, but was amazed to find few specifics or pictures. 

Bueler,

Beuler,

Bueler?

Anyone?

[79coyotefrg]

I have a 79 with the original L43 4 speed in it behind a recently rebuilt 20/22r hybrid. I am running Old Man Emu springs with the stock hangers and 5" shackles with stock driveshafts. I just picked up a used R151 turbo tranny that is complete with bellhousing, transfer case, and shifters. I would like to put the tranny in as is(and put 4.7 gears in the transfer case at some point). I have been searching a bunch about swapping to the newer 5 speed and am hoping for a little more info.

1-Tunnel clearance? I have read about the having to pound out the transmission tunnel to make the newer tranny fit. Does anyone have a pic of doing this and exactly where I need to create more room? My R151 is forward shift so the shifters should stick up in about the same location correct? I'm fine with doing some trimming, just wanted to check.

  no, sorry the shifter holes wont line up. 
the L43 is 2 inches shorter than any other transmission. and our 79's were designed for this short (in height) trans so you will really have to wail on the tranny tunnel to make room or do like I did and just run a 2 inch body lift.  I didnt use a later transmission I went with a L52HD from Marlin because it bolted in like the stock transmission (besides the 2 inch height difference)

2-Crossmember? I have read that you can just spin the existing crossmember around and the 2 existing rear bolt holes line up so you just have to tap 2 new holes. Once again, anyone have any pics? I would like to eventually switch to a budbuilt crossmember but if it is easy to use the stock one for now I'll do that.   

   not sure about that flipping it around but you can easily slide the crossmember back by using some old ubolts over the frame.

3-Clutch? I have also read that I have to run a newer clutch master cylinder and slave cylinder. Should I just get the entire clutch assembly off a newer truck? Or can I just add a slave cylinder and use my existing master and line? The R151 has the clutch fork on it. Also, my clutch and flywheel are still in good shape. Can I use them or do I need to get a different clutch?

get a slave for the R151 and use your existing line and master

4-Driveshafts? I know the transmission is 4" longer. Will a front d.s. out of a 84-85 (or a clearenced IFS d.s.) be the correct length? Does anyone know what this length is? With the same thought, I think a 84-88 rear d.s. from a 4runner or SB will fit. Again, do you know the length? (seems like people have driveshafts sitting around but they don't exactly know what they are out of so some measurements would help when I am looking) I don't want to have my existing d.s. modified because the front spline has a lot of play and I would have to ship them somewhere to have it done.

the R151 is 6 1/2 inches longer than the L43  but still,  you can find drive shafts from a 84-88 truck and be almost perfect.   you will need to drill your pinion flanges because the later drive shafts used larger bolts and have a different bolt pattern.

That is a lot of questions, but I know there are at least a few people on here who have done this exact same swap(or a W56).

hope I have helped.

[scheefdog [OP]]

Thanks for the reply and info 79coyote. That answered a lot of my questions.

Sounds like I will just have to go for it with regards to the tunnel clearance and crossmember to figure out how to make it work.

I'm thinking you meant the R151 is 4 1/2" longer (not 6 1/2")? I looked at Marlins transmission table that has lengths and the L43 is 20.875" and the R151 is 25.5". When I measure the transmission on the truck(not the most accurate measurement) and the R151 I get about the same.

I picked up a set of driveshafts that are from an 84-88. The front is about 25 1/4" collapsed and the rear is about 44 1/2" collapsed so hopefully they will work. I have the newer style diff flanges on my axles already because I swapped to newer 3rds so they will bolt up. Looks like I will have to drill the flanges on the r151f transfer case. They appear to be a 65mm spacing instead of 60mm.

Do you know if I can use my existing clutch and flywheel with the new trans? I'm thinking I just need a new throwout bearing kit for the R151.

[79coyotefrg]

was it the w56 I'm thinking about being 6 inches longer  

yes  a r151 throwout bearing and a slave cylinder.