which to use up front, '69 cj5 or '78 cj7 diff?

[rocmoc]

I have a '69 CJ5 V6 which I am being back from the dead. I do also have a '78 CJ7 auto six banger that I use for parts. Both have the front diffs and the '78 does have disc brakes. I already have a 70s flanged diff with a Detroit in the rear of the CJ5 . The CJ5 front diff has matching gear ratio but the '78 does not. Which diff should be used? and the money does matter! Is there that much advantage to the open knuckle diff?

Thanks,
rocmoc n AZ/Mexico

 

[tarry99]

The open knuckles are easy to service , but maybe the best part is the 1978 Dana 30 had the big disc brakes on it. ????????????

 

[Sasquach]

Do you still have the stock brake system? The Dana 30 with discs would be the way to go but will open a can of worms with the frame mounted M-cylinder and obviously a new R&P. The track width may be a bit wider? on the 30 if that maters to you-not sure about it though.
As far as the closed knuckle 27? the weak points are the knuckle pivot bearings and as mentioned the servicing aspect were it requires disassembly to grease the components.
I think ultimately you are going to want to get the Dana 30 in there if not now then later when $ is available.
My 2 cents.

 

[tarry99]

Do you still have the stock brake system? The Dana 30 with discs would be the way to go but will open a can of worms with the frame mounted M-cylinder and obviously a new R&P. The track width may be a bit wider? on the 30 if that maters to you-not sure about it though.
As far as the closed knuckle 27? the weak points are the knuckle pivot bearings and as mentioned the servicing aspect were it requires disassembly to grease the components.
I think ultimately you are going to want to get the Dana 30 in there if not now then later when $ is available.
My 2 cents.

Track width on the Dana 30 is 3 inches wider, but the spring perches are in the same location as your old front end at I believe 28" c/c. The master cylinder can be an easy fix as Herms Overdrives sells a replacement frame / mounted floor Master cylinder for Drum rear and Disc's front. As Sasquach mentioned that still leaves changing the Ring & Pinion.
Good Luck!

 

[rocmoc]

Keep it up & thanks!

So would the money be better spent doing a disc brake conversion on the '69 matching ratio diff then messing with changing the ratio on the '78? The '69 has been entirely serviced & repaired as needed where the '78 has not yet been touched. Width would not be a problem as the 17" rims I will be running will require a min 1 1/4" spacer so no spacer would be required in the front, only the rear.

rocmoc n AZ/Mexico

 

[tarry99]

Keep it up & thanks!

So would the money be better spent doing a disc brake conversion on the '69 matching ratio diff then messing with changing the ratio on the '78? The '69 has been entirely serviced & repaired as needed where the '78 has not yet been touched. Width would not be a problem as the 17" rims I will be running will require a min 1 1/4" spacer so no spacer would be required in the front, only the rear.

rocmoc n AZ/Mexico

I think you answered your own question, the 69 is serviced and ready to go. It really depends on which Jeep "YOU" really like! When you get some money get the 78' Dana 30 ready to go with the right ratio as it is almost a direct bolt in, along with the fact its a better front end with open knuckles and it has disc brakes. The Master cylinder conversion I think is about $AMC 150 +/-. Like I said before it's 3 inches wider. The only other thing we have not mentioned is whether or not you still have the old Ross steering in the 69? Moving the Dana 30 over to the 69 would require a steering gear change. Perhaps to manual Saginaw box or a power Saginaw box. Again not a big deal as thousands have been installed in early Cj-5s.
Think about which Jeep will better serve your purpose, Nothing you do is not without some cost.

 

[rocmoc]

Thank you tarry99. Already have the power Saginaw box so the peddles will be the only major work.

Thank you again,
rocmoc n AZ/Mexico

 

[tarry99]

Thank you tarry99. Already have the power Saginaw box so the peddles will be the only major work.

Thank you again,
rocmoc n AZ/Mexico

The peddles are really no issue ......I'm assuming you still have the pedals through the floor with the frame mounted Master Cylinder??..........I have that same system in my CJ5 and although you have to be smart while installing the supplied bracket from Herm's Overdrives and make sure you have proper alignment with the Master Cylinder push rod it works just fine with the Disc's up front and the 11" drum brakes in the back. The kit also has a proportioning valve that needs to be plumbed in.
These short CJ5 's seem to work quite will with a non power brake setup with the disc's up front............Of course if you have huge wheels & tires then stopping may be another issue but anything around 33" is just fine.

 

[rocmoc]

I still have the original pedals and will be running 33's and never larger.

Thanks,
rocmoc n AZ/Mexico

 

[73CJ]

I got a YJ pedal setup on eBay for $20.

Then you can go hyd clutch and new style brake master cly. The best part is the disc brake setup.

Use the D27 until you are ready to put the Dana 30 in. Then go Dana 30 , PS, tilt wheel & hydro clutch. All assuming you plan on keeping it.

 

[tarry99]

I still have the original pedals and will be running 33's and never larger.

Thats good like I said check out HermsOverdrives,com he has taken a late model 2 chamber master cylinder and built a conversion bracket and it fits right where the original frame mounted M/C is now. This Master cylinder is setup for disc' s front and drums in the back and works quite well.
Good Luck on your project!

 

[rocmoc]

I got a YJ pedal setup on eBay for $20.

Then you can go hyd clutch and new style brake master cly. The best part is the disc brake setup.

Use the D27 until you are ready to put the Dana 30 in. Then go Dana 30 , PS, tilt wheel & hydro clutch. All assuming you plan on keeping it.

I am keeping her long-term. Let another go like it in the 70s and was sorry since then. Won't make the same mistake twice!

Thanks,
rocmoc n AZ/Mexico