Dillonn
Registered User
This is a great old truck my kids even love it but the above combo just doesn't work. Its really spinning at 60Mph. Any suggestions?
86 6.9L with C6 and 3:55's needs and OD bad!
- Thread starter Dillonn
- Start date
DesertBen44
Full Access Member
I dont really know what to suggest but an aftermarket overdrive like a gearvendors. the no OD is teh weak point of the durable ford and chevy 3 speeds from back in the day
idiabuse
Full Access Member
235-85-16 tires are tall, helps a bit depending what you run now.
Javier
Javier
I have 4.10s in my 86 with C6 and 6.9 and I definitely know what you are talking about. I run 265/75s and have quite a few R's under the hood, so I have toyed with the idea of either changing the rear end, running taller tires, putting in an OD tranny, or some combination of the above. But the truck also pulls like a **** and I still get really decent mileage so it's all still under debate for me. Still I know a decent set of tires is needed so going taller would be easiest.
You will find out the tranny options for these engines stink. I thought maybe if we could adapt a 700r4 to these engines that might be the route to go, but a little searching revealed they have their own set of problems. Your only option is a 5 speed zf with it's flywheel problems, or the e4OD and the wiring and computer you need to run it. And it's going to need a rebuild also if it's a pre-95 model.
The add-on overdrive units that bolt on the back of the tranny or transfer case are a option, but you still give up some rpm's and fuel mileage from the slippage of the c6. I drove a 96 powerstroke the other day with the E4OD, and taking off from a stop reminded me of the c6 my truck used to have and why I didn't like it. It's like driving a boat, The rpms raise up and it seems like it takes forever for the truck to move out.
The add-on overdrive units that bolt on the back of the tranny or transfer case are a option, but you still give up some rpm's and fuel mileage from the slippage of the c6. I drove a 96 powerstroke the other day with the E4OD, and taking off from a stop reminded me of the c6 my truck used to have and why I didn't like it. It's like driving a boat, The rpms raise up and it seems like it takes forever for the truck to move out.
Oog
Full Access Member
You guys need a 4wd zf-5?
Darrin Tosh
IDI Hound
One of the best and easiest ways to get OD is to go with a Gear Vendors Unit. You can pick them up off Craigslist for under $1000.00 if you do some searching. New ones are $2,800.00 or so.
This will drop your highway rpm cruising by 500 rpm's
This will drop your highway rpm cruising by 500 rpm's
no parts hustlin' in the tech section.
that's what the marketplace is for.
sle2115
NRA LIFE MEMBER
You sure you got 3.55's? What's the tire size? If you in fact have 3.55's and think it humming at 60, try 4.10's...that's near governor speed with standard height tires. Do you have a tach, what are your RPM's at 60 MPH? With stock tires, around 31" tall, at 60 with 3.55's, you should only be turning about 2300 RPM's. 4.10's you are looking at 2800 RPM or so. If you are off the 2300 number with stock height tires, you may have some slippage issues. I had 3.55's with a 1:1 4 speed (no OD) and it turned exactly 2325 RPM's...not really bad. Gov speed stock is around 3400
Darrin Tosh
IDI Hound
Good point....
Dillonn
Registered User
That sounds like good advice, where can I buy a tach for this truck. It's possible that trans is slipping.
sle2115
NRA LIFE MEMBER
There are several options, one is to put a tach sensor in and put a factory on in the dash. There are also aftermarket ones that you can find to work with mechanically injected diesels, you'll have to do a little digging to find them, but they exist.
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