99 Suburban 6.5 to 5.9 Cummins Swap

[usanumber1]

A 1st gen Cummins 2wd 4" OD downpipe attached to a mid-mount exhaust manifold will tuck down between the bottom two bolts of trans adapter on passenger side, another option would be a Cummins cobra-head down pipe.

I'm running an HE351CW with a low-and-back exhaust manifold, and I already have a 4" stainless mandrel 90* attached to it still from the original downpipe I had built. Should be fairly simple for someone else to whip up a small section.

 

[usanumber1]

Don’t have the clutch starter safety wired in, but I do have the NSS wired up so it starts. Just waiting on driveshafts to show up from High Angle Driveline and I’ll be cruisin.

Also scored a stick diesel cluster. I wanted the completely refurbished one on eBay, but I couldn’t justify the extra $100.

 

[Husker6.5]

Pictures?

 

[usanumber1]

Just got the cluster installed. Took it the new one apart, tried winding the tumbler for 30 minutes to match it with old, then realized I could just swap the “face” of the cluster assembly and entire tumbler.

 

[FellowTraveler]

Just got the cluster installed. Took it the new one apart, tried winding the tumbler for 30 minutes to match it with old, then realized I could just swap the “face” of the cluster assembly and entire tumbler.

That is a very nice interior...

 

[usanumber1]

That is a very nice interior...

Thanks, it will all be deep cleaned and chipped, cut, cracked, pieces replaced. Goal is to have it look factory new. Planning on new carpet and reupholstered leather too. But that’s a bit down the road.

 

[usanumber1]

I got rear driveshaft in and have been test driving it to make sure everything is squared away. One problem I’ve found, is the brake system is building pressure, and then they start dragging. The pedal eventually gets extremely stiff. My research has given me some possible culprits, as this has never happened before.
A) too much fluid in master cylinder
-I removed some fluid, had a minor affect
B) leaks in booster, needing a rebuild.
-I ordered a rebuild kit just in case, haven’t removed the MC yet.
C) booster pedal linkage is too long
-this seems plausible, as I swapped in a manual brake pedal, but I recall them having the same dimensions and proportions. I’m not sure if manual and automatics have different hydro boost units, I’d presume not.

which route would y’all go first?

 

[ak diesel driver]

I had that issue once and it was the rod length

 

[usanumber1]

I had that issue once and it was the rod length

How do I determine proper length?

 

[ak diesel driver]

It wasn't on a gmt 400 but I did find a free play spec. 25 years ago but if IIRC mine was actually pushing the master cylinder in a bit when installed

 

[n8in8or]

How do I determine proper length?

Can you reinstall the auto brake pedal and see what kind of freeplay you have and then make adjustments so the manual pedal has the same?

 

[usanumber1]

Can you reinstall the auto brake pedal and see what kind of freeplay you have and then make adjustments so the manual pedal has the same?

So I pulled the booster thinking I could easily replace the pedal push rod, wrong. Then I started taking a closer look at the pedals, and then remembered a YouTube video where he cuts the tread part of the pedals and swaps the small manual one onto the automatic. And what I noticed was the placement of the pushrod studs are different. I measured my old auto pedal and the ‘new’ manual pedal and the placemat of the studs is definitely different. See attached photo for comparison. I need this dumb think moving NOW so I guess I’m pulling the dash again to swap pedals.

 

[Will L.]

Too much brake fluid can NOT cause it. The volume from master to slave cylinders (or calipers) stays exactly the same regardless of amount in reservoir. If it is low, air can get drawn in.
If too full it will simply spill out the top lid seal. The system runs really high pressure and the lid seal barely holds a dozen psi at best.

 

[usanumber1]

For anyone thinking you can just swap pedals, this apparently makes a difference:

 

[ak diesel driver]

I'd probably make an adjustable rod

 

[FellowTraveler]

For anyone thinking you can just swap pedals, this apparently makes a difference:

The distance between the holes determines the pedal ratio...if I remember right "the rod from the pedal to the booster will have some play to compensate for the slight difference in angle".

 

[FellowTraveler]

Here is a helpful link for hydroboost...I rebuild my own hydroboost units simply because I have had nothing but bad results with rebuilt units from parts houses.
The most common problem "is dirt & other things like internal hose desegregation". One speck of sand can and will scratch the main piston causing leaks between the M/C & booster vent.
A hydro inline filter is best advice for sandy environments is it a vent filter which must be fabricated.

10 Tips For Servicing Hydroboost Brake Units

Learn about hydroboost brake systems, their benefits, functioning, maintenance, and troubleshooting tips in this informative article.

www.brakeandfrontend.com

 

[Will L.]

@FellowTraveler
Care to expand on the filter?

 

[FellowTraveler]

@FellowTraveler
Care to expand on the filter?

Well an inline hydro filter is made for high psi hydro systems and placed between the high pressure hose and booster.
The vent filter, is simply a fitting fit into the vent that is just a notch under the hydroboost where it meets the M/C. The notch can be filled in w/JB weld and dab of silicone rtv spread over the JB on the inside, this is to prevent brake fluid or p/s fluid compromising the JB material.
From here a hole needs to drilled close to where the notch was on the hydroboost and tapped for whatever fitting you would like to use finish off w/short hose and a $3 fuel filter or run up high and out of the way.

The other areas prone to sand ingress is the M/C when being serviced and the p/s steering pump when being filled.

 

[usanumber1]

Just drove again, did the same thing, booster is toast. I ordered a rebuild kit yesterday, but I need this thing movin ASAP. At least I know how to remove a booster quickly now lmao