CUCV gearing

[Truck]

Okay for those of you with CUCVs (6.2L/TH400/4.56 gears/235-85r16 tires) what have you done to make your vehicles drivable on the street/highway. Mine winds out pretty high on the highway. I know what can be done: swap to higher gear, get overdrive tranny, put on bigger tires. But I want to know what have ya'll done that has worked for you.
Cheapest seems to do tires. Will a 34" tire be enough to help? I really don't want to change gears if I don't have to. I use this to pull my Jeep and trailer. Tranny swap seems aweful expensive. But I'm open to know what has worked for all ya'll.

Truck

[ 01-14-2006, 04:48 PM: Message edited by: Truck ]

[NH2112]

Bigger tires will be the cheapest and easiest fix, but there's no mechanical reason why the truck can't be driven at highway speeds in stock form. Your ears may not appreciate the engine running near the redline but the engine won't mind one bit. I'm not sure how much tire can fit under a stock-height CUCV but I'm pretty sure 34s are too tall unless they're real skinny, like the Super Swamper 34-9.50s.

[twaddle]

I use a M1008 daily as a service vehicle and I sympathise with you on the torture that highway speeds can be and I'm half deaf (born that way, nothing to do with the truck or working on Caterpillars).
The other thing is that an overdrive would improve the fuel economy a fair bit and also cause the engine to last longer.

Be careful going for 34inch dia tyres, I use 285x16 General tyres and I find they get a little close to the wheel arch when turning, 34inch tyres might catch.

I have bought a new 4L80 but haven't got round to installing it yet but I would suggest a rebuilt 700R4 with a Diesel spec torque convertor.
This would retain the low gearing for heavy towing and offers a higher O/D gear for cruising than the 4L80 does.

There is no real cheap fix on this situation unless you get the chance of a complete truck with more suitable gearing that can be parted out.

Other than the gearing and the basic comforts the M1008 truck has been one of the most reliable trucks I've had.

Regards

Jim Twaddle
Biggar, Scotland

[Barry Nave]

Jim
Is this your main ride or you have other diesel?

[twaddle]

The M1008 is used mainly as my work truck as a self employed Caterpillar engineer, I've had it over 8 years.
The American trucks are rare over here in Scotland and its also something of a hobby for me plus using them for business/work I can off set the costs against my tax.
I also have 96 K1500 6.5 Suburban that I bought in Texas in 2001 ans a 1991 Volvo 940 estate (runs on petrol and LPG) which is the family run around.

Also have various others including a 42 Ford GPW and a 1989 Mercedes G wagen (engine in bits on the merc at the moment).

Regards

Jim Twaddle
Biggar, Scotland.

[britannic]

I installed a custom HD 700R4 along with 285/75/16 tires, this allowed for 3 figure freeway speeds with my M1028, powered by the "Britannic Special".

[Truck]

Brit, Do you have 4.56 gears? Ballpark what did a HD 700r4 run you? Don't know if I have the coin to do that, but it would be nice. I do have a 700r4 out of this 2wd suburban I just stripped for my 6.2l/Scrambler project. Tranny needs rebuild, but it might be something to start to work with.

Truck

[wthif]

Originally posted by Truck:
Brit, Do you have 4.56 gears? Ballpark what did a HD 700r4 run you? Don't know if I have the coin to do that, but it would be nice. I do have a 700r4 out of this 2wd suburban I just stripped for my 6.2l/Scrambler project. Tranny needs rebuild, but it might be something to start to work with.

Truck He has 4.56 gears and I would guess the transmission cost about a grand. He installed the trans himself. The 700r4 was a K case and now resides in my truck with the rest of his drive-train excluding the axles.

I would talk to Bowtie Overdrives or some of the other tranny builders people have used in this site. You'll find an overdrive trans is really nice. You'll also have to get a new T-case or change input shaft on yours.

[85-m1028]

I run 35" tires and that puts me at about 50mph @2200 rpm "stock suspension" as long as I go about 50-55 I can sqeeze out about 15-16 mpg. I am debating a well built 700r4 myself and think that this is really the best solution for a daily driver the lower first gear ratio and overdrive add alot of versatility, but a t-case change up and drive shaft mods would be in the works too. the only draw back I can see to a 700r4 would be lighter towing and payload capacity, but just how much is debatable? I plan to use my truck for off roading and mostly work so the investment would be warranted. a good highway speed would about 65mph which would be about 40-42 tire with a three speed auto No sense in giving up the 4.56 gears and locker that made this truck desirable to me!! but a lift and tires would be a wash as far as cost between them and a 700r4

[Truck]

85-m1028, How do your 35s fit with stock suspension? Do they rub at all in the front? I'm not worried about the back because I have a utility box bed and can easily open my fenders.

I also won't be wheeling this truck. It is my tow rig/trail maintaince for my Scrambler. I do drive it without towing and would like to lower my rpms & get a littler better milage.

Truck

[85-m1028]

I fitted the 35" tires with a little fender trimming and banging out the lower inner fender wells behind the tires, I used 17"x9" steel rims with a heavy offset and I don't get any rubbing at all "even bottomed out at full stuff"

pictures at Steelsoldiers.com in the photo gallery section under 85-m1028, I have since painted it back olive drab but there is a pic of the tires

[snoman87]

Originally posted by Truck:
85-m1028,
I also won't be wheeling this truck. It is my tow rig/trail maintaince for my Scrambler. I do drive it without towing and would like to lower my rpms & get a littler better milage.If your not going to be wheeling it then regear. As you lift and put bigger tires on you increase you drag therefore decreasing your fuel economy. The cost of a lift, and new tire would probably be the same as rear gearing, you could sell the 4.56 to offset the cost. What you gear to would depend on what OD tranny your eventually going to go to ... which you will even if you re-gear.

[85-m1028]

I think the carriers will need to be changed out if going to anything 4.10 and numericaly lower, which means either a new detroit or an open carrier. You could probably find used ones snd save some $$.

If you swapped in a 700r4 and 35" tires on stock suspension and 4.56 gears that would put you @ 2145 rpm'S at 70mph in overdrive that sounds pretty good to me!!

[ 01-16-2006, 08:01 PM: Message edited by: 85-m1028 ]

[britannic]

As wthif said, I do have the stock CUCV 4.56 gears. My "Bad Boy" transmission (not Ballpark's) cost me $2K, including HD convertor; it had all of the HD goodies for handling power and torque and the warranty was excellent, as was the builder's after care and tech help getting the conversion fully functional.


Originally posted by wthif:
</font><blockquote>quote:</font><hr />Originally posted by Truck:
Brit, Do you have 4.56 gears? Ballpark what did a HD 700r4 run you? Don't know if I have the coin to do that, but it would be nice. I do have a 700r4 out of this 2wd suburban I just stripped for my 6.2l/Scrambler project. Tranny needs rebuild, but it might be something to start to work with.

Truck He has 4.56 gears and I would guess the transmission cost about a grand. He installed the trans himself. The 700r4 was a K case and now resides in my truck with the rest of his drive-train excluding the axles.

I would talk to Bowtie Overdrives or some of the other tranny builders people have used in this site. You'll find an overdrive trans is really nice. You'll also have to get a new T-case or change input shaft on yours. </font>[/QUOTE]

[snoman87]

Originally posted by 85-m1028:
35" tires on stock suspensionThat's a whole lot of fender trimming ... I am running 285/75R16's (33's) and I get a little fender rubbing without verh much articulation when turning. I know time to get the hammer out!!!

[dieselcrawler]

When I first got my 1028, I ran 35's with fender triming on the front, none on the rear. Worked out ok, stock suspention. At that time, the 6.2L was without the turbo, and stock 4.56 gears. Worked well for me, nice ballance of power/rpms. I have another K20 I just got a few months ago, (a gasser, I hate to admit) and am running the same set up, only with 4.10 gears. It also does well. I hope to get a 4" lift on the K-20 soon, just like the look better... more ground clearance under the T-case...

Good luck...
Greg