Project BigB... a 1977 Dodge Van 6x4!

[Keyblazer]

I did my numbers carefully...
I think this will be close.
Dimensions
Tire A: 305/70 R 16
(33 x 12.01 x 16)
Tire B: 285/75 R 16
(33 x 11.22 x 16)
Difference
Width -0.79" (-20.00mm)
Sidewall height +0.01" (+0.25mm)
Overall height +0.02" (+0.50mm)
Circumference +0.06" (+1.57mm)

If your speedometer has been calibrated for 305/70 R 16 (33 x 12.01 x 16) tires, replacing them with 285/75 R 16's (32 x 11.22 x 16's) would result in the speedometer reading low by 0.06%.

 

[ujoint]

Be careful with those Weld's, they were known to creak. I know it sounds weird, but they way they're designed causes them to creak & make noise!

 

[Keyblazer]

I would not be surprised... the fake beadlock is a seperate piece..

 

[r_w]

You can run different tires front and rear like that, but you NEED to measure the exact tires you are running--don't just rely on the spec numbers.

You can compensate for minor differences by playing with air pressures, but that is a tradeoff on tire wear.

 

[Keyblazer]

Updates...
Good and bad..
Good:
I found a used set of 285/75 16 Nitto Terragrapplers to match the rears...

Bad:
Got 2 of them mounted and went the the van to see how it worked....
Only to find that the 8x16 wheels I got in the previous post were not 8 on 6.5" PCD as the guy I got them from said, but 8 on 170mm..... I felt stupid cos I didnt check them with my PCD gauge...
Still, I think I can get my money back out of them..

Good:
Got a oil pressure gauge from Harbor freight... like $16 with the coupon!
First I earthed the pressure sensor wire to the block and watched the original cluster gauge max out to 100psi... so that looks ok.
Next I plugged the HF gauge in and started the motor....
A solid 85psi from cold, and warmed the motor up... hot at idle reads 50psi... phew!

Good:
Removed the hand controls, and it went smoothly!

Bad:
A short drive(not on the street) revealed a lack of brakes... until the pedal was mashed, then the front locked(dirt road).
Fluid was full but looked dirty, so I sucked out and refilled with fresh. PITA, cos there is minimal clearance between the Master Cyl and cowl panel. Can barely get the top off!

An hour of sucking with my Mityvac and pumping with my foot, gave me very little fluid out of the rear brakes, but the fronts bled fine...
Puzzled, I gave up for the day.
Both rear axles have fluid now flowing out but its slow going. I am a little confused... the is a brake fluid line going into the trailer brake controler under the dash, and everytime I pumped the pedal the lever on it moved.
With all that traction and weight on the rear two axles I am thinking a adjustable brake balance valve might be a good idea...

 

[xped]

The brake lines are known to swell shut. Replace them and try again.

 

[Keyblazer]

Again, great info!

 

[Michael Slade]

I think you should look at a GM Hydroboost setup out of a late 80-'s van. They have a stepped fluid reservoir and would/should fit right in there w/out all the funky vacuum booster crap.

I am running Hydroboost on my big ******** CrewCab Land Rover and it is amazingly strong.

Just a thought...

 

[wrcsixeight]

I don't know about a '77, but my '89 has a proportioning valve. It is not adjustable to my knowledge, but perhaps your could be stuck, and allowing only slight hydraulic pressure to reach the rears. There is a single wire going to it that illuminated the parking brake light when one of the start adjusters fell out in the drum.

Here's a diagram of a Ford one, the Mopar looks similar.

I must also depress my brake pedal further than most any other car I've driven. Could be a Dodge Van thing. The first application when driving another vehicle is always a little shocking.

There is the possibility of adjustment on mine, but the whole booster must be removed to get to it.

Are the brakes on the Tag Axle hooked up?

 

[Keyblazer]

Thanks for that info, and in fact you are correct, according to the Haynes manual there is a twin piston in the Master Cylinder that triggers the brake warning lamp whch is on. I was alone, and it says you need 2 people to reset it. One to push the brake pedal and the other to release a union to "Recenter it". I will be out there in a few days and hopefully someone will be there to assist.
Yes, the brakes on the Tag axle are functional!

 

[Keyblazer]

Seems the above info was wrong... the brake proportioning valve is downstream, not on the master cylinder... I assume it will be on the chassis rail on the drivers side... thats where the hard line go.

 

[wrcsixeight]

Mine is almost directly under the MC, on the frame rail. If you wanna pay for my gas from SD to OC and back, You've got a helper.

 

[xped]

If it has sat for along time without being driven the master cylinder maybe bad. Every vehicle I've restored that has sat has had to have it replaced. I would still check those brake lines, the swelling shut info came from a Dodge truck forum.

 

[Keyblazer]

I agree with you, based on the condition of the front hoses, I plan to replace or rebuild all the braking system, but hoped to just get it home first, rather than it being 80 miles away from all my tools.
The PO, say the pedal went right to the floor when he started, and moved it after its 5+ year slumber.
The brake warning lamp is on, and it feels like there is two stages to the pedal travel. The first stage I feel on the pedal gave me no braking, and the second locks the front wheels easily.
This adds up to info I read about the brake proportioning valve applying pressure to the rear drums until the pads contact, or if the travel is exceeded, the piston in the valve moves over triggering the warning lamp and cutting off flow to the rear brakes to stop fluid loss.
Reading the manual in detail I think I get it now. You have to release the front bleed nipple to recenter the piston, reversing the original issue.
The lack of brake pressure in the rear circuit, closed the valve.... because I could not get fluid into the rear circuit, there was no back pressure when I bled the fronts, that would have normally done the recentering of the piston.
I think that I will go out there again next week and replace the rear flex hoses, and try to recenter the brake proportioning valve again.

 

[Keyblazer]

Digging into the brake issue threw me a great idea.
There are cost effective kits out there for converting the rear Dana 60 drums to disc brakes. This improves braking/are self cleaning and saves about 50lb per axle.
Here:
http://www.virginia4x4.com/dodge dana 60.html

With all the weight I have out there and the plan to do some off road stuff, that might include water crossings, I thinks it would be good!

Oh, in an earlier thread, someone said about the turning circle... and it is bad!
I assume it is limited by the steering lock available more than anything?

Researching the Vancharger/pathfinder conversion, I found this cool stuff!

Whats funny is that the top pic is exactly like the one that was the base for my Van...

Oh, and the thick pile of receipts I have in the folder add up to about $60,000 in work over a 20 year period!