Just wanna tow a 2000lb. Trailer up a hill..

[Schurkey]

The step bore in the LD 400 MC is largely to blame for the ****** feel. I have a heavy duty 400 MC with my hydroboost in my 1500 and I believe it is a single bore.

If you have low-drag calipers, you need the extra capacity of the quick-take-up master cylinder which provides an initial "shot" of high volume/low pressure fluid to push the pads against the rotor. Then the high-pressure section of the master cylinder takes over.

If you don't have low-drag calipers, you wouldn't need the step-bore master.

Using a non-step-bore master with low-drag calipers results in a low brake pedal. Using an (incorrect) larger-bore master in place of the smaller-main-diameter step-bore, would help with that, but the hydraulic advantage is gone. Maybe doesn't matter with Hydroboost.

 

[Bowtiefresh]

I installed new brakes flushed the old brake fluid, new master cylinder and still had mushy brakes. So thats why I installed the gmt800 mc, I dont know the difference but now my brakes are way better.

There's all these threads and posts about GMT800 master cylinders on GMT400 trucks. I don't doubt you fixed a brake problem, but no-one can tell me what's different in the newer master cylinder that accounts for the improvement (except that it isn't defective.)

I figure you could have fixed your brakes by installing a non-defective master cylinder that actually fit and didn't need adapters, cheaper than buying one that has to be cobbled into place.

 

[RDF1]

Buy a wrecked escalade that has the 6.0 H.O. LQ9 motor and tranny. 345 HP stock. Just saw one go for $1200 in SoCal

The only "issue" there is the poor transmission. And that 345hp is up there around the 5500rpm area.
I towed a many miles with a Turbo LQ4 and it was amazing how well it pulled a heavy trailer at 70 MPH @ 2000 RPMS. But had to run 93 octane.

 

[RDF1]

I installed new brakes flushed the old brake fluid, new master cylinder and still had mushy brakes. So thats why I installed the gmt800 mc, I dont know the difference but now my brakes are way better.

I did the Hydroboost from a C3500 and Master cylinder
Cardone Select 13-2535
with 2500 calipers on front and new wheel cylinders on the rear, SS lines Front and rear.

Brakes work great. No Mushy stuff. But i dont tow with it either

 

[Supercharged111]

Mine is very similar. 3500 factory HB, 2500 HB MC (same as a dually but smaller reservoir), 2500 calipers, 1 new wheel cylinder, and stainless lines. If my rear was an 8 lug it'd be an otherwise matched factory braking system. Schurkey what trucks had low drag calipers and associated master cylinders?

 

[L31MaxExpress]

wanting to drive 75 pulling a trailer with likely no brakes pulled by a truck that is well known to have inadequate brakes in stock form.
I don't mind topping the hills a little slower and upgrading brakes so I have something going down the other side.

Something is definately wrong. I have towed a 5,000 lbs trailer with a Nissan 4.0L V6 in a Pathfinder. It runs up steep hills in 3rd gear at 4,000 rpm but still running 70 mph. There is a nice long grade climbing into Jacksboro on 380 and most of the time I am in the fast lane passing slower moving vehicles. 4.0L V6 only makes like 280 TQ. Why is this pertinent you may ask. 280 tq @ 4,000 rpm is just over 210 hp which is what the TBI 350 is roughly rated. 210 hp is more than capable of pulling 10,000 lbs GCVW up a 6% grade at low elevation at 70+ MPH.

 

[L31MaxExpress]

I had the same problem. Albeit trailer was bit heavier. Problem solved. Not cheap tho...
I like the Escalade thing. Or a 6.0. The tbi SB just wasn't a work horse. And maybe 4.10 diffs...but 4.56 won't run 75 unless wide open. Be screaming.
A good bigger engine is likely, in the long run, the cheap way to meet your goals. If you do your own work. A 454 will bolt in. They are cheap. Go carb.

I had the same problem. Albeit trailer was bit heavier. Problem solved. Not cheap tho...
I like the Escalade thing. Or a 6.0. The tbi SB just wasn't a work horse. And maybe 4.10 diffs...but 4.56 won't run 75 unless wide open. Be screaming.
A good bigger engine is likely, in the long run, the cheap way to meet your goals. If you do your own work. A 454 will bolt in. They are cheap. Go carb.

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I have 5.13 gears in my Express van with a 4L85E and do not have that issue at all. It runs ~3,000 rpm @ 75 mph and feels like it could pull a house off its foundation from a stop.

My suggestion is gear the truck to where the engine will run uphill in 3rd gear very close to peak HP at the speed you want to run. On a TBI 350 that is 4,000 rpm. Would need your trans type and tire size to calculate the gearing needed. With a 700r4 that would put you in OD cruising at 2,800 rpm @ 75 and 3rd gear would give you 4,000 rpm @ 75.

Gearing will make the trans live longer and usually ends up towing better than adding power in the higher rpm bands.

 

[L29Sub]

700R4 OD will be 0.69. 15" tars? We can figure this out, scientifically (like global warming) if "I Wanna Tow..." will post details such as tire size, tire diameter.
I plugged in the Express Van with 4l85e (OD 0.75), stock tires at 30.5", and 5.13 rear at 3000 RPM. Equals 71 mph.
I don't deny small blocks can't be used for such. GM ran SBs in ton and a half trucks for years. They got the job done, but they never saw 75 mph. And they were not really even OTR trucks. They had 5 speed/2 speed. And 24" tires. Still 60 was it.
A healthy 350 with a good 4 barrel manifold and a Q'jet and cheap shorty headers will smoke a stock tbi. I'm old school.. very old school. Running down the road at 3500 RPM is painful. IMHO.
My thoughts are 4.10 and 3rd gear uphill? At least it's driveable as a normal vehicle.





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[L31MaxExpress]

700R4 OD will be 0.69. 15" tars? We can figure this out, scientifically (like global warming) if "I Wanna Tow..." will post details such as tire size, tire diameter.
I plugged in the Express Van with 4l85e (OD 0.75), stock tires at 30.5", and 5.13 rear at 3000 RPM. Equals 71 mph.
I don't deny small blocks can't be used for such. GM ran SBs in ton and a half trucks for years. They got the job done, but they never saw 75 mph. And they were not really even OTR trucks. They had 5 speed/2 speed. And 24" tires. Still 60 was it.
A healthy 350 with a good 4 barrel manifold and a Q'jet and cheap shorty headers will smoke a stock tbi. I'm old school.. very old school. Running down the road at 3500 RPM is painful. IMHO.
My thoughts are 4.10 and 3rd gear uphill? At least it's driveable as a normal vehicle.

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LT265/75R16s on it. 31.7" tall. Speedo is accurate to the radar speed limit signs.

Mercruiser Vortec 350 will run WOT at 4,800 rpm all day.

ALL cars with an old 3spd ran 3,000 rpm @ 70 mph in the 50s, 60s, and 70s and nobody batted an eye.

GM ran 350s in C60 based 71 passenger school buses and trucks too. Deep gear.

My great uncle had a 63 C60 on the farm and it went to town for farm stuff. 327 2bbl with a governor. 4spd and a 2 speed rear end. I drove it numerous times as a young adult. The governor kicked in around 4,000 rpm and limited the truck to ~62 mph. No problem running that speed loaded even as long as you did not have a steep hill.

I will take a moded TBI over that Q-Jet 350.

 

[L29Sub]

Your tires are too tall. ;o)
This is an engine designed to pull. None of that sissyfied tbi stuff. And, it'll run a hundred at 3000 RPM. All day. By golly.
I will take my leave now.

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