IDI Newbie
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Senior User
Joined: Jun 2000
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From: Calgary Canada
IDI Newbie
Hi there just picked up an '88 F-250 with the 7.3 and a Banks kit. I am completley new to Diesels, but not to Ford Trucks. 
What kind of RPM is this truck safe to run at on the highway? I'm not sure what gearing is in it but it pulls about 2900rpm at the speed limit. (3spd trans, C6? ) It has Boost and EGT gauges, what are normal operating ranges on these as well (empty and towing a 6000lb trailer)? Is 15w40 diesel spec oil okay to run, or should I use straight 30W when towing in the summer? I am going to change all the fluids in it this weekend, then off to the dyno next week to get an idea of the power it makes and to check the speedo calibration.
Thanks, Dustin.
What kind of RPM is this truck safe to run at on the highway? I'm not sure what gearing is in it but it pulls about 2900rpm at the speed limit. (3spd trans, C6? ) It has Boost and EGT gauges, what are normal operating ranges on these as well (empty and towing a 6000lb trailer)? Is 15w40 diesel spec oil okay to run, or should I use straight 30W when towing in the summer? I am going to change all the fluids in it this weekend, then off to the dyno next week to get an idea of the power it makes and to check the speedo calibration. Thanks, Dustin.
i ain't rite
Joined: Mar 2005
Posts: 65,579
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From: Marlboro Mental Hospital.
2,900 is a safe speed, the injector pump is governed at 3,300 rpm.
boost should be kept under 15 lbs, and exhaust temps should be kept below 1,100 degrees. you did not mention what type exhaust is on it, but if it has the banks system, you should see around 250 hp on the dyno. my 88 runs 325 hp on the dyno with the modified intake and custom dual 4 inch exhaust without mufflers.
boost should be kept under 15 lbs, and exhaust temps should be kept below 1,100 degrees. you did not mention what type exhaust is on it, but if it has the banks system, you should see around 250 hp on the dyno. my 88 runs 325 hp on the dyno with the modified intake and custom dual 4 inch exhaust without mufflers.
Elder User
Joined: Sep 2004
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From: Peoria IL
Have fun at the diesel pump if it runs 2900 rpms on the highway. I can do 90 mph at 2900 and I can literally watch the gauge drop if its on the rear tank.
Why would you want to put 30w oil in your engine? Any diesel ive seen has 15w-40 in er, even my diesel lawn mower. I prefer Rotella T myself.
Why would you want to put 30w oil in your engine? Any diesel ive seen has 15w-40 in er, even my diesel lawn mower. I prefer Rotella T myself.
i ain't rite
Joined: Mar 2005
Posts: 65,579
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From: Marlboro Mental Hospital.
the 325 hp was with the 3 inch intake direct to the turbo from the grill, and 4 inch exhaust from the bellhousing to the 4 inch y pipe at the transfer case to the 4 inch stacks with no mufflers. boost was 18 lbs at 3200 rpm, and egt was 1200 degrees.the injector pump was turned up 3 flats. it has since been detuned. there are sidepipe inserts in the stacks, and the pump was turned back 1 1/2 flats. it now runs 7-10 lbs boost and 700-900 degrees egt at 3200prm, with 260 hp. i got tired of looking at the clouds of black coming out of the stacks... it looked like a super stock tractor hooked up to the sled going down the road, and only got around 8 mpg.. plus, you could hear me coming from 1/2 mile away.it now just gives a puff of black at takeoff, and i can sneak up on you till you hear the motor rattling.
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From: Calgary Canada
I just checked the door sticker and the axle code is 39, which is 3:55 correct? Does that RPM sound right for a truck with 235/85/16 tires, 3spd trans, and 3:55 gears at 110kph/ 68mph?
Post Fiend
Joined: Nov 2003
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From: Nutter Fort, WV
2900 RPM with a C6 and 4.11 rear on 235/85-16 tires = 65 MPH
2900 RPM with a C6 and 3.55 gears on 235/85-16 tires = 75 MPH
2900 RPM with a C6 and 3.55 gears on 235/85-16 tires = 75 MPH
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If your looking for a good oil for the IDI the Petro Canada Duron 15w-40 is it I have tried Chevron Delo 400 it turned black pretty quick. The Duron stayed cleaner longer.
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From: Calgary Canada
Well I changed all the fluids last night, while the diff cover was off I confirmed that it's definatley an open diff with 3.55 gears. 
So I'm hoping maybe it has the wrong speedo gear, it's running a tan gear right now. Also what diff is in this truck, maybe a Dana? I'd like to now what my options are for upgrading to traction-lok. I also checked the SCA's, trans fluid and filter, engine oil and filter, fuel filter, did I miss anything? 
So I'm hoping maybe it has the wrong speedo gear, it's running a tan gear right now. Also what diff is in this truck, maybe a Dana? I'd like to now what my options are for upgrading to traction-lok. I also checked the SCA's, trans fluid and filter, engine oil and filter, fuel filter, did I miss anything?
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The rear axle is most likely a 10.25 Ford the front axle will be a Dana. As for fluild changes-Coolant,Engine Oil,Diff oil,Transmission oil,Power Steering fluid,Brake Fluid and Clutch M/C Fluid.
With the power steering you can take a turkey baister to suck the old fluid out and replace it with new stuff. With the brake fluid wash out the baister with some brake clean and then suck the fluild out and replace it with new brake fluid. The best way to flush your brakes is through the bleeders but 99.9% of the time you will never get the bleeders loose.
With the power steering you can take a turkey baister to suck the old fluid out and replace it with new stuff. With the brake fluid wash out the baister with some brake clean and then suck the fluild out and replace it with new brake fluid. The best way to flush your brakes is through the bleeders but 99.9% of the time you will never get the bleeders loose.
Post Fiend
Joined: Nov 2003
Posts: 21,285
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From: Nutter Fort, WV
The rear axle should be a 10.25" Sterling.
Front axle will be a Dana 44 IFS if it is a regular cab.
Front axle will be a Dana 50 IFS if it is an extended or crew cab.
My speedo gear is teal for 3.55"s.
It is dead on with 285/75-16 tires.
Don't forget the SCA for the antifreeze when you change it..
Front axle will be a Dana 44 IFS if it is a regular cab.
Front axle will be a Dana 50 IFS if it is an extended or crew cab.
My speedo gear is teal for 3.55"s.
It is dead on with 285/75-16 tires.
Don't forget the SCA for the antifreeze when you change it..
Last edited by Dave Sponaugle; Nov 5, 2005 at 05:41 PM.
