2500 RPM @ 55 MPH Help!

[kristhewelder]

Gear ratios?

Hi I have lurking learnt for a while. My 2001psd wrecker with 4.88 gears would go 63in 3rd gear and 95 in overdrive.myE350 fan 7.3 IDi C6 trans will run 80. Its like you have noO/D or a different rear gear.good luck

 

[Diesel JD]

Hi I have lurking learnt for a while. My 2001psd wrecker with 4.88 gears would go 63in 3rd gear and 95 in overdrive.myE350 fan 7.3 IDi C6 trans will run 80. Its like you have noO/D or a different rear gear.good luck

Precisely! These trucks were designed for a 55 national speed limit. For that a C6 and 4.10s were not bad, especially when diesel was 10 or more cents cheaper than [email protected] in the new normal it is just not acceptable for most people.

 

[flareside_thun]

There is an under/OD unit for sale in the marketplace here...for 120 bucks plus shipping you can't beat that with a stick.

 

[GOOSE]

You really have to lay out what you expect from the truck. 4:10's and a C6 give you about the worst gearing available for interstate cruising for sure but a very good rig for towing 50mph around town. Keep in mind if you do the R&P swap to 3:55's or even 3:31's you will still only have 3 forward speeds. This forces your engine to operate way out of its "sweet spot". Diesels have a narrow range where they are most efficient, around 16-2100 rpm's give or take. Maybe this could be a 2 part project for you, 3:55's and a zf to follow when funds arise and a deal presents itself. Gear vendors or a brownie are the ultimate, allowing the 500rpm drops between any gear but usually have the price tag that none of us like. Good luck in your decisions.

 

[DontKnowJack]

Therein lies my dilemma. I want the truck to do both! Now realizing thats not possible without spending a ton of money, I think I'm going to leave the 4.10s in there and put a ZF5 in it and see what happens.

 

[Diesel JD]

The ZF and 4.10s work well. We have members who get 16+ mpg on the highway with that combo and a light foot. Its just that to avoid the worst of the fuel mileage penalties you'd need to stay in the 55-65 mph range t avoid going much over 2000 rpm, there you'll have plenty of power. Oldbull said you weren't able or willing to do this swap yourself, but if you're comfortable wrenching on vehices including engines and transmissions, most of it is plug and play as long as you're careful. The clutch hydraulic assy is tough and any driveshaft resizing should be left to the professionals. Beyond that, it's not hard, just tedious and time consuming and all these parts are heavy. Best case scenario is find a willing mechanically inclined friend with a nice workshop and treat them right for their help, whether that's some cash, barter some services or whatever. That's how I've gotten all of my BIG projects done. Always with somebody who would let me watch or help so I could learn. I'm not a real mechanic but I have learned a ton since beginning the IDI journey, and have gotten some awesome projects accomplished with the help of some very talented friends/acquaintances.

 

[DontKnowJack]

Thanks.
I am able and willing, just don't have the knowledge. I have the tools and a friends place to do it, just never done it before. I've had diesels for ten years but IDI's only for two yrs. I sure would hate to mess it up. lol

 

[Fordsandguns]

If you can find a donor truck with the ZF that isn't running for cheap it isn't that hard to do. I suggest using a donor because you will have everything you need if the donor is all there to begin with and you can see how it all goes together as you pull it apart. It makes it much easier. I need to see things to understand what I am doing most times. It's harder for me to grasp it be reading unless I have done it before. When I did my swap I had never done one before and I did lots of reading here on OB before starting. It helped but there were some things that didn't click until I saw them in person.
It is intimidating at first, but once you get into it, it's not as bad as you imagined it would be.

 

[Diesel JD]

Being a mechanically handy guy who is willing and able, I think the most likely place you'd screw up is on the clutch system hydraulics. Before you do anything to the firewall you'll need to either run down one of the firewall reinforcement kits or buy one from a member here that makes them. I'm thinking this is Freebird01 but I may remember wrong. Otherwise it is plug and play....very heavy plug and play though. It would be best as Fordsandguns has indicated to at least find a truck with a ZF in it to grab. That way you can at least have the experience of removing the transmission yourself as well as grabbing the other stuff you might need. Ideally you want one that is already from behind an IDI, that way your speedometer and everything else will work normally. The ZF5-S47 from behind a Powerstroke pre 99 at least will bolt right in but you may have to switch to a different kind of speedometer. I will check on that for you if it becomes an option as I know someone who knows exactly what that particularly swap entails. You're also going to have to decide if you want to use a factory style DMF or a SMF like an LUK. Also you could look up a thread by "Cheaper Jeeper" who did the ZF5 swap and SMF with off the shelf autozone parts and a LOT cheaper than an LUK. Was it perfect...maybe not but it worked flawlessly for him.

 

[DontKnowJack]

This is exactly what I'm talkin about JD. I can turn a wrench but have no idea what a DMF or SMF or LUK is! Lord help me.

 

[Diesel JD]

Well to be honest, I don't know that much about them either. My conversion from C6 to a T18 was much simpler. The T18 uses a SMF (single mass flywheel) only. The dual mass flywheel was a contraption Ford used to dampen engine vibrations. Allegedly the DMF is needed to protect the ZF trans and keep gear noise at tolerable levels. Others like LUK offer a single mass flywheel conversion and say that all it is is noise and it isnt hurting anything. Opinions around here differ. Dual mass flywheels are expensive, and some say they can't be repaired but I've heard others put that into dispute as well. A good guidline would be if you grab a ZF grab the flywheel that came with it and if it is in decent shape, just run it and don't worry. Also worth noting is you really NEED to get a new throw out bearing when you do all this work (cheap) and upgrading the pilot bearing to a kevlar pilot bushing was a real nice upgrade to my conversion especially since I used a custom built mechanical clutch linkage, to reduce clutch effort.

 

[DontKnowJack]

You really have to lay out what you expect from the truck. 4:10's and a C6 give you about the worst gearing available for interstate cruising for sure but a very good rig for towing 50mph around town. Keep in mind if you do the R&P swap to 3:55's or even 3:31's you will still only have 3 forward speeds. This forces your engine to operate way out of its "sweet spot". Diesels have a narrow range where they are most efficient, around 16-2100 rpm's give or take. Maybe this could be a 2 part project for you, 3:55's and a zf to follow when funds arise and a deal presents itself. Gear vendors or a brownie are the ultimate, allowing the 500rpm drops between any gear but usually have the price tag that none of us like. Good luck in your decisions.

Goose I'm leaning toward a brownie. Can you or anyone else steer me in the right direction?

 

[GOOSE]

Here is an old thread with some info to offer.

http://www.oilburners.net/forums/showthread.php?t=37757

There is a link in there to Anderson Brothers. They have a selection of them for sale. The 5000 series are plenty stout for our rigs. From what I have seen, most people get their boxes from local salvage yards, or an occasional Ebay listing. Craigslist also may present one from time to time. These were common in 50's and 60's trucks, F600's, Chebby C60's and the like.

This project will require a competent welding skills at the minimum and a drive shaft shop to cut and modify your current set up. I have dug up info elsewhere. Do a search here, RLDSL has one and is well versed on them. I believe the Stovebolt forum has some good info on them also. Good luck if you choose this route.

 

[Diesel JD]

Hey guys...regarding the brownie, I have one sitting on the floor in my garage and I'm on the fence as to whether to try to tackle the install soon. Not sure if it should really require extensive weling/fabbing skills. Lately my thinking has been to hang that auxillary so that the output yoke is right where the current output for my carrier bearing is, that way shorten the front driveshaft and leave the rear alone. I would cut and mod a couple piecces of bedframe steel and drill them for the holes to hang the brownie. 2 crossmembers with 2 grade 8 bolts and some sort of vibration dampening material should be more than enough to support that box. It looks like to me the shifter will just easily poke through the 4X4 shifter hole on the appropriate floor pan. I know the shift linkages and getting the driveline angles will be tedious. I'm on the fence. Need to make a few decisions soon, but when that brownie does get installed I will share a complete account with lots of pictures with everyone here.

 

[DontKnowJack]

Sixteen revolutions of the driveshaft = 8 revolutions of the rear wheels, plus a couple inches. What gears do I have?