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-   -   LT1 Auto to 5 speed conversion (http://www.jeepforum.com/forum/f12/lt1-auto-5-speed-conversion-1430055/)

87TPIYJ 10-21-2012 07:47 PM

LT1 Auto to 5 speed conversion
 
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I have an LT1 with a 700r4 transmission in my 87 YJ. The transmission went out so I'm converting it back to a 5 speed (originally a 5 speed 4 banger). I went to a junk yard and picked up a NV3500 with an NP241 out of a 98 1500 pick up. I also got the 4wd linkage, front drive shaft, clutch, flywheel, and master cylinder all for $100 woohoo!

Attachment 494178

This will be a long process because the next steps are expensive. I still need to get an SYE and new front and rear drive shafts made.

I do have a question about the master cylinder. Is anyone running a nv3500? If so can you use the stock jeep master cylinder or will I need to use the GM master? Thanks, I post pics and updates as they come.

yjtyler 10-21-2012 07:53 PM

i got both my d shafts cut/lengthened, balanced and a new u joint in one for $200. that trans looks different from mine. is that an internal slave cyl? maybe mine isnt a true nv3500..

87TPIYJ 10-21-2012 07:58 PM

Yes it is. I believe the older models came with external. What year is yours?

Opihi59 10-21-2012 08:48 PM

Amazing deal you got there. I would have supposed the shifter alone for the trans would cost $100. I don't see it in the photo but hopefully you got it with the package. My feeling is that you had better stick with the Jeep master--the rod length and pedal hook up could be problematic. You will need to rig up some sort of unique hydraulic line between the master and slave quite likely.
Would be nice to watch you do this build, take a lot of photos and post up as you work your way thru the process.

87TPIYJ 10-22-2012 04:04 AM

Yes I hope I can use the jeep master, but that depends on if it can move the slave cylinder correctly. If anyone out there has done this please let me know!

87TPIYJ 10-22-2012 04:27 PM

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So I think I have found a master cylinder that will work. Willwood sells a compact master cylinder that will bolt up and fit behind the booster. I need to find out what bore size I will need (they make 6 sizes). I will also need to make a way to attach it to the pedal. Here is are some pics. What do you guys think?



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Opihi59 10-22-2012 04:41 PM

You don't have to move a large amount of fluid to work a clutch, it's not like a 6 piston brake caliper. I would go with stock until you find there is a problem, then start looking into spending money. That one does look nice though, and with the threaded rod you can very likely adapt that to the pedal connection.

87TPIYJ 10-22-2012 04:50 PM

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I have been reading around and I have been getting the vibe that the stock one will not move enough fluid to push the Chevy pressure plate. My master cylinder is shot so I have to buy a new one anyways. That's why I want to do it right the first time. I am trying to research and find the volume of fluid that my slave takes to operate (98 Chevy 1500 z71 pick up 5.7L). I'm watching another thread with that has almost the same set up (his has external slave I have internal). We both have not decisively answered the master cylinder question.

Oh yeah looks like I will probably need to get a new clutch and turn the flywheel. The springs are still tight in the disc though. Here are some pics.

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87TPIYJ 10-22-2012 05:25 PM

Ok so a lot of info updates tonight. I have found some numbers I just have to make since of them.


Slave cylinder bore size: 30.6mm= 1.204"

Jeep master cylinder bore size= .7"
Jeep stroke length= ? (appears to be about 1.2")

Wilwood bore sizes= .875", 1", 1.125"
Willwood stroke length= 1.12"

So the question is do I want to be as close as possible to the slave bore size? How far does the slave need to travel to fully disengage the clutch?

yjtyler 10-22-2012 06:48 PM

I got a new clutch because the old one was shot. But it was only like $35 to get the flywheel turned and $20 for a new ring gear.

87TPIYJ 10-23-2012 03:50 PM

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Got some of the parts cleaned up tonight. I really wish the PO did not screw something into the 4wd shifter indicator housing. Any ideas on filling the holes? I plan on painting it black.

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Opihi59 10-23-2012 04:10 PM

Smooth over the holes and apply some sorta outrageous sticker on it, alternatively drill out a big hole and stick some sorta gauge in it. :2thumbsup:
Glue the base of a cup holder on it...

87TPIYJ 10-24-2012 05:16 PM

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Well I pressure washed the tranny and transfer case. I also split them apart to whenever I get the money I can put an SYE in. Yjtyler I see the fitting that you cut, but I don't understand how I would hook it back up to the transmission. I understand how to get a custom line and hook it up to the jeep master cylinder. Thanks for the help.

Here are some pics from today.


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Attachment 495903

Here is the fitting that hooks up to the Chevy master cylinder

yjtyler 10-25-2012 04:30 AM

Yeah in not sure about the internal slave but the external is just pipe threads

87TPIYJ 10-29-2012 07:37 PM

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Got the transmission dropped tonight. Tomorrow I will start on the interior and floor board.



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