Alternate OD options for a TH400

[tiresmoke!]

Hey gang, been a while....

Well, looks like my late father's 1990 Chevy 3500 1-ton dually ext.-cab is coming home with me. Not a bad old truck....med. metallic blue, stainless wheel simulators, aluminum diamond-plate running boards and I think a Lund visor. Will get some pics when I go to retrieve it in a few weeks(it's at his buddie's place right now, dad parked it due to a leaking rear wheel brake cylinder). Only body issues are a slight amount of cancer in the ext.-cab corners(where thay all get eaten up...will adrress that one quickly). The fact that it was the newest vehicle my dad ever owned, and that it's kind of a rare bird around these parts factor into me keeping it and not just fixing and flipping for profit.

This has the TBI 454(the original overheated Rat was replaced with one from a 1991 454SS), and the original TH400. Yup, ol'smoke finally has a big-block.

Granted, it's a 1-ton dually, and urged by a big-block....it ain't a fuel miser, and nothing short of converting to electric power will make it so.....but would be nice to have some kinda OD to make it a bit more liveable on longer road treks.

I know they were offered with the TH7004R's, as well as the NV 5-speeds...but converting to the 5-speed is a gamble(most of those were junk anyhow), and the TH400's are a stronger transmission than the 700's ever thought of being(IMHO).

Looking for suggestions for OD alternatives.......not going to drive it all the time, but would like to be able to take it on longer road trips without having to remortgage the house for gas money.

[SpiderGearsMan]

4L80e but they suck
Nv4500 was strong ..but autos are better to tow with or plow snow ...is this the old square R/V Body or the Newer C/K ?
the difference id a juice clutch for manuals ,,th 400 is a rock

[tiresmoke!]

It's the "newer" C/K, Spidey(as in the 88-98 "new" bodystyles).

I've only seen 1, MAYBE 2 extended-cabs in the older 73-87 "square" bodies, and those sure looked like aftermarket conversions to me.

I love the idea of a row-yer-own in this truck , but it's kinda pointless to swap out a perfectly good TH400 to me....it's what's keeping me from doing the 7004R or the newer 4L80e's.

[HoosierL98GTA]

Hey dude long time no hear, or see for that matter. Especially since we're only probably 30 miles apart. Anyway , I'm surprised after driving a semi all day. (Am proud of you though) you'd even want to row more gears . Only way to go is a Gear Venders overdrive. Just have to compare how much driving it will take to make it worth it. At $4 a gallon , it will be sooner than it used to. You will have to shorten the drive shaft.

[SpiderGearsMan]

700 is too weak ..4L80e goes into convulsions when charging voltage drops ..driving the center support through the case or the band slips ..smoking the drum and planetaries ..biggest problem lately , we have been burning through 4L80e lately ..last one didn't look bad , but felt weak in second and a month later got towed back in with smoked band and got a fresh srta reman ..th cheaper ..+ electronics fun ..

[Beagle]

Dang Smoke, either I missed it or I'm sorry to hear about your Dad. That'd be tough as hell for me. Hope you are doing okay.

I'd do the math on the OD and be blunt with myself about costs. The o/d is almost a bragging thing, depends a ton on how much you plan on driving it. With miles / year and cost v. gas price increases, it gets to be a tough decision. The GV on the 400 seems to be the right answer in my mind, or just back off on the rear end gears? Gears are comparitively cheap... yeah, you lose the hotrod part of it but it's a 1 ton. Let it be a truck... 454 will pull pretty good. It may not be fast but hell, it's a big girl.

[6 Grrrs]

I did a big block in a '91 C3500 Reg Cab Dually that originailly came with a 350 TBI. It did have a 4L80e, so we left it alone (other than PCM programming). I did the Crane EFI cam (which came out of my 454SS with only 12k miles on the cam), Edelbrock Intake, Edelbrock headers, and tried a few different chips from TBIChips.com and still could only muster 6mpg when towing. It got 10 empty whether around town or on the highway. It had 4.10s in the rear and tall tires.

My guess is that mileage aint much better than your TH400 will get. I doubt it is really worth the trouble. Especially when you factor in some type of controller for the 4L80e. The G/V unit is probably the best bet in the end.

BTW the 350 got worse mileage since it had to work so hard. I put it on a chassis dyno before bolting on a Vortech blower. With the outer wheels removed (too wide for the dyno), it made 110 hp and almost 200 ft lbs tq. Never dyno'd it with the blower or the 454 but I'd say we doubled it at least. The dyno we used was my bro in law's and the dually would not fit thru the door to the dyno so we brought it in from the other end of the shop (using a jack and 4 guys pushing). It took over an hour to get it on the dyno. It wasn't worth the effort to do it again. It was my buddy's truck and his intention was to tow his 14,000 lb boat to Florida and leave it for the winter. He towed the boat once with the blown 350 and wasted a head gasket. He was pushing it too hard up a mountain. It towed great with the 454. He has since sold the truck to a guy in Mass.

[SuperBuickGuy]

at 2800 for a new GV overdrive, it'd be cheaper to buy a DD and pull the sledge hammer out when a sledge hammer is called for. Seriously, my brother had a 91 single wheel 1 ton, and even with the OD got 13 mpg - a grand increase of 2 mpg. If you must get better mileage, keep the 400 and put a diesel in the truck (preferably cummins, but a 6.2 would bolt right up... you even already have the hydroboost).

[tiresmoke!]

Thanks for the responses, guys.

Basically...the farthest I'm looking to run this truck is from my home here in Indianapolis, to southeastern Kentucky,and possibly into Tennessee. My in-laws have a 24'-26' travel trailer down south that I'd love to be able to hook onto.... take to a campsite when the family and I go to visit with her aunts/uncles/cousins in the summer. Hotels SUCK...LOL

I'm not expecting big fuel-economy numbers..hell, it's a big-ass 1-ton extended cab duallie with a big-block. Just looking to make life a little easier on that 454 running at 65-70 MPH, and MAYBE just a little easier at the pump. She's no hot rod, for sure...sounds rather healthy through those 2 1/2" straightpipes(the sawed-off little guy that my late father bught it from had the exhaust done...cut the Y-pipe, no converters or mufflers....3 1/2" chromed extensions).


Oh, it won;t be an EVRYDAY driver...still have my '99 Silverado ext-cab shortbed 4x4(from the infamous Red Ball run) for that, the duallie is just something for fun and for when I need something with towing/hauling capacities(wish I'd have had IT for the Red Ball, would've handled Dan's big-ass trailer a lot better).

It's on the obnoxious side of loud, think I may have to toss some mufflers on it to keep the peace(I know, dad, don"t be a puss....LOL)....like I said earlier,when I go to pick it up within the next few weeks I'll snap some pics and toss'em up here.

Thanks for the condolences, lost him back in August(54 is WAAAY too young to go, I at least had 36(almost 37) years with him.

[tiresmoke!]

SBG.....funny you mention the 6.2.(slight diversion from the topic at hand, but is relevant and bears telling)

My Dad had an '86 diesel 4x4 Suburban at the time he bought the duallie...the dumbass he bought the duallie from cooked the original 454, the thermostat stuck closed and he didn't give a damn.

The Suburban's 6.2 was originally of the weak-sauce N/A variety. Somewhere along the line, it had been rebuilt, and as a result received a .060 overbore. Someone also slapped a Banks turbo kit on it as well....Dad had the heads off, welded the crack across the valve seats(guess this is a common issue)...did something to the fuel pump, all I know is the smoke would ROLL and that big red hulk would FLY.

Tried to talk him into yanking the Banks-urged 6.2 from the rotting Suburban and shoving it into the duallie(would've been a good 1-ton ext-cab duallie truck with that "Hot Rod Detroit" as he called it), but no dice. He found a 454 from a wrecked '91 454SS, and went from there.