brake upgrade???
Thread Starter
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Postmaster
Joined: Jan 2010
Posts: 4,319
Likes: 4
From: Elk City, OK
i dont recall my 4th gear rpms, but in 5th (od) im 2000 at 70mph. my truck is all torn apart right now, installing an intercooler, getting my radiator boiled and a leak sealed, replacing all my hoses and installing new battery cables.
Post Fiend
Joined: Nov 2003
Posts: 21,285
Likes: 15
From: Nutter Fort, WV
If the speedo has not been recalibrated, stock 235/85-16 tires with 3.55 gears and a ZF 5 would be running 70 MPH at 2050 RPM.
However the tire size change has you running 83 MPH at that RPM and speedo indicated speed.
On the 90 model you change gears in the transmission or transfer case to correct the speedo error.
What is the trailer you are pulling?
Something is wrong if it is still nose low with the truck on 37" tires.
I have to run a 4" drop hitch with 33" tires and no air bags.
However the tire size change has you running 83 MPH at that RPM and speedo indicated speed.
On the 90 model you change gears in the transmission or transfer case to correct the speedo error.
What is the trailer you are pulling?
Something is wrong if it is still nose low with the truck on 37" tires.
I have to run a 4" drop hitch with 33" tires and no air bags.
Thread Starter
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Postmaster
Joined: Jan 2010
Posts: 4,319
Likes: 4
From: Elk City, OK
i dont go by my spedo, i go by my gps. ive got a 2 car trailer, 7k axles, its a high deck. sits about 40 inches deck to ground. 32 1/2' long. it had 4" drop axles on it, my driveway has a crazy low dip in it that the city wont let me level it off and put a water pass drain under it. i put on straight axles on it to clear. its got a 6' dove tail that drops the rear about 20" off the ground. with my 1 car trailer i run a 10" drop and it rides perfect.
Lead Driver
Joined: Dec 2006
Posts: 6,496
Likes: 94
From: So. Jersey
Um, pics, maybe a little write up in another thread, I'm very interested in this too.
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Post Fiend
Joined: Nov 2003
Posts: 21,285
Likes: 15
From: Nutter Fort, WV
I can't offer any help with the Chevy unit, but the Ford unit was bolt on and play.
Hydraboost bolted right up to the firewall.
Brake rod was the correct length to hook to the brake pedal.
Hoses fit like they were made for my truck.
Master cylinder bolted right on.
MSLC, if he was the one, did mention the master cylinder to hydraboost holes were the ones he had to enlongate if I remember right.
Hydraboost bolted right up to the firewall.
Brake rod was the correct length to hook to the brake pedal.
Hoses fit like they were made for my truck.
Master cylinder bolted right on.
MSLC, if he was the one, did mention the master cylinder to hydraboost holes were the ones he had to enlongate if I remember right.
Postmaster
Joined: Apr 2008
Posts: 4,802
Likes: 1
That's correct, the Ford master cylinder needed the holes elongated outwards cause the studs on the hydroboost are further apart than those of the vacuum booster. Also, the pedal pushrod for the hydroboost is longer than the vacuum booster part, so the hydroboost unit needs to be spaced out away from the firewall, 2" was what I ended up at IIRC. Finding an F-Superduty hydroboost is definitely the easy way to go.
Thread Starter
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Postmaster
Joined: Jan 2010
Posts: 4,319
Likes: 4
From: Elk City, OK
i think i scored big time today. i bought a 63 scout for $200 this afternoon. a ton of **** inside it..... was going though it and BAM, found a hydroboost! not sure what its off of yet. ill check it out when i get back into town monday or tuesday. so, how do i post some pics on here?
Thread Starter
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Postmaster
Joined: Jan 2010
Posts: 4,319
Likes: 4
From: Elk City, OK
3.73's and big loads with 40" tires, better get a couple boxes of U joints.
I broke enough with 235 tires behind a stock 6.9.
Now with a modded turbo 6.9 and 285 tires, driveshfts last about 2 years, U joints last about 4 months.
4.56 gears with 40" tires would be about the same as 31" tires (235/85) and 3.55 gears.
On a 90, my guess is you have either 4.10 or 3.55 gears.
Give me a speed and RPM in 4th gear and I can tell you what gears you have now.
Also has the speedo be corrected for the tire size change?
Going from the stock 31" tires to 37" tires have created an error in the speedo reading.
235/85-16 tires with 4.10 gears would run 59 MPH at 2000 RPM in 5th gear.
Running 37" tires on the same setup at the same RPM in overdrive would be 71 MPH.
Jump to 40" tires, 2000 RPM in overdrive would be just shy of 76 MPH.
Don't forget, double the braking performance will mean you have to run double the brake line pressures.
So brake lines and hoses will be under rather extreme pressure.
Driveline and brake components have to run at 128% of the stock load to be even with what it had with stock tires.
Figure 2,000 PSI brake line pressure stock, with 40" tires that has to be 2,560 PSI to be even braking force.
I broke enough with 235 tires behind a stock 6.9.
Now with a modded turbo 6.9 and 285 tires, driveshfts last about 2 years, U joints last about 4 months.
4.56 gears with 40" tires would be about the same as 31" tires (235/85) and 3.55 gears.
On a 90, my guess is you have either 4.10 or 3.55 gears.
Give me a speed and RPM in 4th gear and I can tell you what gears you have now.
Also has the speedo be corrected for the tire size change?
Going from the stock 31" tires to 37" tires have created an error in the speedo reading.
235/85-16 tires with 4.10 gears would run 59 MPH at 2000 RPM in 5th gear.
Running 37" tires on the same setup at the same RPM in overdrive would be 71 MPH.
Jump to 40" tires, 2000 RPM in overdrive would be just shy of 76 MPH.
Don't forget, double the braking performance will mean you have to run double the brake line pressures.
So brake lines and hoses will be under rather extreme pressure.
Driveline and brake components have to run at 128% of the stock load to be even with what it had with stock tires.
Figure 2,000 PSI brake line pressure stock, with 40" tires that has to be 2,560 PSI to be even braking force.