2600-2800 rpms at 55 miles per hour???

[Julianq7]

I have a 1988 Ford F-350 7.3 with a c6 transmission. I don't know if it's not shifting right or if it was how the truck was made but at 55 miles and hour it reaches 2600 rpm on the last gear. I can go faster than 55 but I don't want to be cruising at 3400 rpm in a diesel on the highway. Is there a defect in the transmission? Or is this how the truck was built? I read up on gear vendors website that I can make the 3 speed I have now into a six speed. Has anyone tried gv? They are expensive but if it is worth it I can do it.

Any help is appreciated!

 

[rdoimages]

That's probably about right if you have 4.10 gears. I have a GV on my C6 and it works nicely to bring the rpm down. Mine is lacking the control unit so it doesn't function the way a complete GV unit works but I'm not really doing much highway driving.
You can run these trucks all day at redline as long as your cooling system is functioning properly and you EGT's stay good.


89 F-350 sc 2wd DRW 7.3 ATS 088, C-6 with Gear Vendor and a rats nest of wiring that was free with purchase.
00 Excursion limited, 6.8 4x4
2001 Jeep Cherokee Classic Sport 4x4 4.0 auto

 

[MTKirk]

I have 4.10's and a T-19 manual and cruise just slightly faster than that. I don't think the old C6's ever make it to fully 1:1, they always slip a little. So I think that's about right if you have 4.10 in the rear. Remember, when these trucks were made there was a 55mph national speed limit. I thought about an overdrive, but my truck won't pull my camper over 65 anyway, so why bother. Can't give up the 4.10 gearing either, truck would be useless to me with any higher a starting ratio. I've just accepted it takes me a little longer to get there.

 

[towcat]

everything you ever needed to know about your auto trans explained here.
just reconfirming hell has a special spot reserved for me.

 

[gandalf]

everything you ever needed to know about your auto trans explained here.
just reconfirming hell has a special spot reserved for me.

Calvin, you're mean, treating a newcomer that way. Be nice and maybe I'll bring you some beer.

In actual fact I think many of us are on that same train headed toward Hell.

I picked up the brake shoes. Junior has the money. Thanks.

 

[jayro88]

4.10s and a c6 is going to give you some pretty high rpms. My van has a c6 and 3.54s.
1. You could swap rear ends, but then you would lose some towing ability.
2. You could swap transmissions to a zf5 manual or an e4od automatic to get OD and a more efficient drivetrain.
3. You could add an auxiliary OD unit. A gearvendor is the only one avialable new that i am aware of. I picked up a DNE2/ US Gear unit used from a forum member for my van.
4. If you wanted the best of both worlds, you could install 4.56s for the added towing, then do a transmission swap with and add the auxiliary OD. You would end up with more grunt down low and lower hwy cruising rpms with double OD. This is what i want to do.

 

[Julianq7]

Thanks guys, I like the transmission swap idea, throw a manual in the beast. That or gear vendors which ever comes out to be less expensive

 

[chris142]

I have a 4 speed and 3.55 gears.im doing 2900@70 mph. I have ran it harder.like the day we had a fire and I was trying to get home asap. It was against the 3800 rpm governor for a couple of hrs

 

[riotwarrior]

I swapped out a c6 for a zf and it was massive change in drivability.

 

[Julianq7]

I swapped out a c6 for a zf and it was massive change in drivability.

How much did that cost you? and is that the manual transmission?

 

[mcghan]

5.turbo,bertha has zf and 4.10s,turbo made it a different truck