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Unread 01-09-2015, 06:45 AM   #1
raven3
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1973 CJ5 
 
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Location: Bakersfield, CA
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73 brake proportioning valve

The 74 & 76 CJ service manual indicates a brake proportioning valve
was incorporated in the braking hydraulic circuit with stock drum brakes, front & rear.

The 79 CJ service manual indicates a combination brake proportioning valve with hold-off metering delay to the front brakes and front to rear pressure control proportioning with stock front disc and drum rear brakes.

On the 73 with stock front & rear drums brakes, did the hydraulic brake circuit incorporate a proportioning valve, like the 74 version?

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Unread 01-09-2015, 07:01 AM   #2
roadhog304
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I do not think there was originally. I do know that on my replacement lines on my 73 I have no proportioning valve. I still have drums at all 4 corners also.
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Unread 01-09-2015, 07:06 AM   #3
OleBlue73
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Correct no valve on a 73
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Unread 01-09-2015, 08:32 AM   #4
raven3
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Thanks a bunch
Have done so many modifications on my 73 since, 1976 lost track of what was OE.

Converted front to disc in 1979 and installed a separate pre 71 hold off valve on the front brake line to delay application of pressure to the front disc brakes, so the rear drum shoe mechanism had time to catch up to the front disc brake.

Since was still using stock manual master cylinder with no vacuum assist power unit, thought needed all the available pressure to both front and back, so did not install a combination hold off delay & proportioning valve.

Often pulled a light weight 4 X 6 trailer made from a 1956 Ford F100 with no braking problems.

Removing the separate hold off valve to experiment on any negative front braking lunge affects.
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Unread 01-09-2015, 01:36 PM   #5
JeepHammer
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1973 CJ5 
 
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Location: South West Indiana
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Everything on my '73 was 'FUBAR' when I got it,
But when I did the disc brake conversion, there wasn't any valve or place to mount one.

I did find out in a big hurry that I needed one since the front discs liked to lock at random times, especially in tight corners.
I used a '79 master cylinder, same year as the front brake donor,
Once I put in a combo valve, the front lock up issue went away,
So did an issue with fronts holding back pressure, even with the back pressure valve removed from the master cylinder.

Never had the back pressure issue before or since on a conversion, probably just an anomaly with the master cylinder,
But since the combo valve fixed it, I didn't take time to track it down.
Several years without problems, didn't even remember it until this thread reminded me.
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Unread 01-09-2015, 08:16 PM   #6
raven3
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My disc front brake donor was from a toyota land crusier and installed in the 73 without any modifications.
The Landcrusier must have used a dana 30 front axle, same as the 73 CJ.

Got a non Jeep pre 71 Hold off valve and installed it on the front disc brake line. Believe 71 was the last year for this type of valve. Brakes worked without any problems. Was considering update by installing a combination valve ,
used in Ford trucks from 73-79 that incorporates both the metering hold off section & proportioning section.
After considering both options will use the front disc hold-off delay only valve, again.
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Unread 01-09-2015, 10:16 PM   #7
CSP
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Toyota Land Cruisers have a six lug pattern, so something seems odd with that statement of the donor. Toyota has never used Dana/Spicer axles either.
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Unread 01-10-2015, 08:12 AM   #8
raven3
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The donor vechicle was not a Jeep, must have been a vehicle with Dana 30 front axle.
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Unread 01-10-2015, 04:37 PM   #9
Partsmke
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Quote:
Originally Posted by raven3 View Post
The donor vechicle was not a Jeep, must have been a vehicle with Dana 30 front axle.
Toyota didn't build a 4 wheel drive pickup prior to 1979. There were a ton of conversions done for 1978 and earlier that were converted using CJ Dana 30 front axles with 6 bolt wheel conversion hubs.
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Unread 01-11-2015, 08:10 PM   #10
jeepdaddy2000
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Quote:
Originally Posted by Partsmke View Post
Toyota didn't build a 4 wheel drive pickup prior to 1979. There were a ton of conversions done for 1978 and earlier that were converted using CJ Dana 30 front axles with 6 bolt wheel conversion hubs.
Actually, they did. The FJ45 started in 63. However, their line of "minitrucks" didn't get a front drive axle till 79.
That being said, all years of Jeep axles and drivetrains were a common 4X4 conversion for both these and Datsun pickups, which means the donor axle could have come from anything.
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