Hello everyone, ive been using DTR for info for a long time, but rarely post. I have a question I was hoping to get some help with. I have a 92 W250 4X4 5speed getrag with 4.10's, stock suspension and 285/70r17 tires. I used to live in california and due to speed limits there (65) would usually cruise at around 70 mph on the freeway. I recently moved to Arizona (75 mph speed limits) and the general speed of traffic in the slow lane between towns is 80 mph. Unfortunately my truck doesnt really like to go above 70mph. it CAN go 80, but gets "loud" and "doesnt sound right", sorry for the horrible descriptions. As far as I can tell I have all the power i should at low speeds, but it seems like my truck should be able to drive faster, but can't. I have searched around and see alot of people mentioning 60 mph top speeds, not sure what would cause a differance in top speeds, as far as I can tell my gearing (4.10) is the lowest available. Basically I'm just wondering if I'm imagining a problem, where there isn't one, or if it is possible that i have all my low end power, but am missing top end power somehow. Sorry for the long-winded post and thank you in advance for any help/input. I Love my truck and don't plan on ever getting rid of it, but can't afford a gear vendor unit, and hate to have semi trucks going around me in the slow lane.

P.S. - with a trailer attached with my ford ranger on it, my truck still seems to have the same 70 mph "ideal cruising speed". leading me to think it isnt a power issue, but i was hoping to hear it from someone else also.

- Branden

 

Do you have a tac?as for speed mine with 37's would cruise at 82 all day long but I know that's with a bigger tire

 

First off nice to see an Arizonan. I have 4:10's and a 5speed and let me tell you I feel the same way. As far as going faster with 4:10's I wouldn't IMO, the fact that you were doing 70 with 4:10's wow I never did. You can re-gear the truck to 3:54's, you could get a 3200 gov spring that will allow more higher revs, but not meant to cruse that high. In all honesty 4:10's is not at all a go fast hiway gear, its made for low end grunt. I do have a GV unit on mine (recent upgrade), and it is night and day from before. Others may come in with better advise, my .02.

 

Add a 3200 rpm governor spring.

 

I don't have a tac. I tried to install one at one time but it didn't work out so well. I found the wiring i was supposed to use and hooked up my tac, but couldnt get any action out of the tac, either the sensor, the wiring, or the tac was faulty, and I never really persued it much. I may end up investing in a gear vendor unit next year. I'm not sure I'd want to regear it, as that is fairly expensive and I'd lose some low end pulling power. I'm a mobile mechanic, so i dont mind driving conservatively on the way home, but it'd be nice to be able to drive 80 mph on the way out to calls. Unfortunately a new paint job is my current highest priority, as my vehicle looks great to me, but kinda has a tacky look to it with the primer peeling and im sure is slightly off-putting to customers.

I suppose I really do need to bite the bullet and do the 3200 spring, I've been wanting to for 3 years now, and haven't mustered the courage to open up my fuel pump. I really don't know why, I'll do anything else on any of my vehicles, but the mechanical fuel pumps on my diesels scare me.

Branden

 

The factory wiring won't work for a aftermarket tach. Voltage in the signal wire is only about 5VDC.

A 3200 RPM gov spring will give you some more rpm but won't really give you what you want. You could put on some larger diameter tires or just bite the bullet on a gear vendors or 3.54 in both the diffs.

 

ISSPRO makes a nice little tach and then you can buy an adapter from them to go from the tach to the factory harnes... I believe its only available over the phone though. So yea ISSPRO makes a plug n' play tach for 92-93 trucks.

As for highway speed, Sounds like you need to install a 3200 rpm governor spring and back you "throttle limiter screw out", its litteraly a screw that stops the throttle linkage on the pump from coming back as far as it can.

If you tweak the pump, add a 3200 governor spring and mess with the throttle limiter screw, it'll do 100+........ Heck the 91 did 101 mph with no overdrive and a stock governor spring

 

3.54 gears made all the difference to my truck. It will cruise 75 all day and 'sound right'. I run up past 85 before it starts to sound like it is wound too tight. When I did my engine swap I had 4.10's in the Ford. I ended up using the Dodge Dana60 front gears in my Ford Dana 60 rear, and a used set of high pinion dana 60 front gears in my front. I was on a budget when I did it so I took a chance on used (make that free) gears. This electrician fumbled his way through it and 40,000 miles later, not a whine or noise from my set up. A mechanic like yourself should be able to make it work.

 

im running the 4:10 with the gov spring, i love the towing ratios, but went for the gv o-drive for the mileage, and xtra ratios, towing with the 5 speed, i get 7 ratios, and picked up 3 mpgs cruising, a worthy investment that pays for itself

 

thinking about it some more, I still want the spring for around town driving, but it won't help me out on top speed at all. I already have "more throttle" i could use, but the truck sounds like it is struggling if i push it down farther, basically, when going 70 on the freeway, im only at partial throttle at the pedal itself, but it seems like thats all the truck wants to use. thanks for all the info guys, def seems like a gearvendor is my best option for a fix.

thanks for the info on the tach, good to know the factory wiring wont work, although im kinda confused why not, all the wiring does is carry the signal.

crossy's son - what gears are in your truck that you are doing 100 mph?

Branden

 

91.0 D250,727,3.07...-SOLD to "JustRamIt"

 

sounds fun, i'd like to be in one of these trucks going 100 to see what it feels like, i dont think ive seen much above 80 in mine.

 

don't ever do it.... its unsafe.

but yea it had a 3spd auto and 3.07 gears and i took the throttle limiter screw out and it did 101.

 

Thats what the spring does man.. it doesn't make it just rev more.

It puts the governor higher in the RPM range so it won't defuel and power won't "drop off" at 2500 rpm like stock.. it'll keep feelin' strong to about 3200 rpm. it gives you more use of the RPM's

 

I have 4.10's , 5 speed and 37" tires that measure 35". I have a factory tach and at 68 mph I'm turning 2000 rpm. I only get 16.5 mpg at that rpm. I'm going to switch to 3.54 dana 80. I think I can get 18mpg or better. P.S. I have the 3200 spring also. Steveinaz