14 bolt 10.5 full float on 1/2 ton

[J011YGR33N]

I’m supposed to be picking up a 14 bolt full float rear end tomorrow for my 87 k15 longbed. Will any modifications need to be made to mount it or will it bolt right up? I did a search on here but didn’t see any threads for my specific application.

 

[nvrenuf]

It'll depend on what it came out of. If it's from a 1 ton, you'll have to move the spring perches and shock brackets. If it's from a 3/4 ton, it should bolt in.

Either scenario will require a conversion u-joint and possible driveshaft length mods.

I'm not sure if the e-brake cables will work.

 

[J011YGR33N]

Thanks, that’s what I was afraid of. Welder it is. I can’t think of the name of the part on the e brake you are referring to, but I read a post that said there was a TSB advising that the valve should be bypass that came on the 1 ton.

 

[nvrenuf]

I was talking about the cables themselves but yeah a 1 ton would have a "load sensing proportioning valve". It's no big deal though, just connect the upper end of the axle's soft hose to the hard line at the inlet side of the valve to bypass it.

 

[J011YGR33N]

Thanks for the feedback. This is my first build so I’m still learning. I wanted the 14 bolt so I don’t have to worry about going through rear ends. I’ll be putting in a 6.0 LS with a th400 behind and with 37” tires.

 

[eskimomann209]

I’m confused why you wouldn’t slap in the 4l80 if you’re already LS swapping it.
The computer is fully capable of handling the electronics.

 

[J011YGR33N]

I’ll switch over to a 4l80 E eventually. I already had the 400. I’m doing frame off so the budget is a little tight right now. I’m building the 400 in class.

 

[eskimomann209]

I’ll switch over to a 4l80 E eventually. I already had the 400. I’m doing frame off so the budget is a little tight right now. I’m building the 400 in class.

Sell the built 400 for money toward an 80.
Otherwise your adding cost down the road.
Budget swaps often get started and then sit.
LS if done before isn’t hard or expensive. But doing it this way, costs more and takes longer.

 

[J011YGR33N]

I get where you’re coming from. The overdrive would be nice but it’s a toy that won’t see the interstate. I’m retired and have nothing better to do so it’ll get done. Me saying budget doesn’t mean cheap, I’m just trying to stay under $25k all in and I’m doing all the work myself.

 

[eskimomann209]

Hmmm. Retired you’ll have to forgive me. I read class and first build. Led me to believe you were slightly younger.
Well I still stand by the statement that it’s redundant to use a 400 with plans to swap in the 80e but it is your truck.
I’m not sure what all is being tallied up for 25 k but I could do a 6.0 and an 80e for well under 8k.
Just depends on how hard the market pins me down with the combo upfront.

 

[J011YGR33N]

I’m taking automotive courses to use up my GI bill. The extra funds I get from that go towards my build. I went with off-road design suspension and there crossover steering to put some perspective on cost.

 

[75gmck25]

The springs on my 14 bolt FF are 52” spacing, which is the most common. Some (or maybe all) one tons used 56” springs, and a couple of postings on this forum said they even had 1/2 or 3/4 tons with 56” springs. You also need to look at the driveshaft connections to see if it matches your current setup for u-joint type and size. Heavier GVW trucks may use a stronger u-joint.

 

[AuroraGirl]

I believe I read that parking brake cable difference to a 1 ton could be different because the frames are different but it also means it was prob dependant on the chassis function and the possible factory use of a prop brake depending on what it was. 1 ton crew? prob cable. But If the cables themselves are different not the brackets or whatever, I imagine the length from pedal to under cab where equalizer or adjuster would be unchanged? but the ones to the drums different length because .. well nvm i dont thing the spot the drum sat changed. Maybe it would be front part since .. no.. okay nvm i just dont know and any reasons I was about to say for why maybe it would be dont pan out. so Definitely research there if you havent.

the TSB mentioned

#88-T-151: REAR BRAKE SENSITIVITY (HEIGHT SENSING VALVE REMOVAL) - (Aug 3, 1988) MODELS: 1984-86 C/K 3500 AND 1987-88 R/V 3500 THIS BULLETIN IS A REVISION OF TRUCK SERVICE BULLETIN 85-B-79, DATED MAY, 1985, UPDATING FOR MODEL YEARS 1984-1988. 1984-1986 C/K 3500 and 1987-1988 RN 3500 series trucks are equipped with a rear suspension height sensing device that optimizes the brake proportioning valve setting for the load the vehicle is carrying. The height sensing system adjusts the brake balance in vehicles subjected to a range of loading conditions. Occasionally, vehicle modifications by body builders or owners influence the height sensing device. If a vehicle has bad rear suspension modifications that affect its trim height or the spring rate, and the driver comments about the brake modulation characteristics of the vehicle, it is recommended that the height sensing system be removed and the brake system be revised as described below: Parts listed below are currently available from GMSPO. 1. Detach rear brake hose from lever and bracket assembly. Reference Figure No. 1. 2. Remove lever assembly and bracket from axle. 3. Install rear brake hose bracket (P/N 348978) and spacer (P/N 2355099) with a 3/8-16 x 1.38 bolt (P/N 358000 - shorter bolt removed in Step No. 2) in tbe upper cover hole. Reference Figure No. 2. Use Loctite 75 or equivalent on the bolt threads. 4. Attach brake hose to bracket with bolt from original installation. 5. Install a 3/8-16 x 1-3/4 bolt (P/N 9439637 - longer bolt removed in Step No. 2) through spacer P/N 14055556 (removed in Step No. 2) in remaining axle cover attacbing hole. Use Loctite 75 on bolt threads or equivalent. 6. Disconnect brake pipes from height sensing valve and brake hose, and discard short brake pipe. Reference Figure No . 1. 7. Remove and discard height sensing valve, bracket, and bolts. 8. Carefully reposition the rear brake pipe, and connect it to tbe rear brake hose. 9. Bleed and test brake system per Section 5 of the appropriate Light Duty Service Manual.

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[Rickf]

You could hang a Gear Vendors OD unit onto the TH400.

 

[AuroraGirl]

for more than a 4l80 lol. BUT if he can stomach the costs either at some point or plan on saving money appropriately, he can have this response:

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