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8.1L/496 Tech

An 8.1L allison and ZF6 arent remotely comparable. Fuck autos behind these engines. I've settled for a NV4500 as the ZF6 are too much $, due to duramax prices and GMs retardation of no manuals early on.
What kind of bellhousing and clutch do you run with an 8.1/nv4500? I have an old 75 GMC c35 that currently has a 4l80e slipping and needs swapped. Thinking about nv4500...
 
The NV4500 came stock behind 8.1L engines in the old body style 2000/2001 HD trucks. The flywheel, pressure plate, pilot bearing etc are the same as all the old school SBC/BBC internally balanced 168 tooth stuff. The OEM flywheel has metric pressure plate bolts and dowel pins for alignment. If you order the factory GM part number for the pressure plate you'll get a Luk SAC clutch cover. They can be a PITA. I decided to go with an old school diaphragm pressure plate with the mounting holes enlarged to fit the metric hardware and drilled for the dowel pins, OEM 8.1L/NV4500 flywheel and a 10 spline clutch disc to fit my transmission's input.

You can use any GM NV4500 bellhousing and an 85-91 square body hydraulic clutch and master to operate either the internal or external slave depending on what year of NV4500 you run. You'll need to make your own hose to connect the two, but the aftermarket has all the fittings needed to put a -3 AN hose between the two. Of course you'll need a high hump transmission tunnel to clear the transmission. You will also need to update the tuning on the engine to suit as well.
 
What kind of bellhousing and clutch do you run with an 8.1/nv4500? I have an old 75 GMC c35 that currently has a 4l80e slipping and needs swapped. Thinking about nv4500...

You can buy a brand new 6.0 bell for about $250 shipped. GM is all the same pattern.
 
Almost.

Sbc/ bbc and ls are very close. But a ls uses the 7th/ top hole that most sbc/bbc dont even have and do not use the 1-oclock hole.

Only a ls nv4500 bell will have the top bolt hole.

Idk if its that big of a deal but ijs
 
The NV4500 came stock behind 8.1L engines in the old body style 2000/2001 HD trucks. The flywheel, pressure plate, pilot bearing etc are the same as all the old school SBC/BBC internally balanced 168 tooth stuff. The OEM flywheel has metric pressure plate bolts and dowel pins for alignment. If you order the factory GM part number for the pressure plate you'll get a Luk SAC clutch cover. They can be a PITA. I decided to go with an old school diaphragm pressure plate with the mounting holes enlarged to fit the metric hardware and drilled for the dowel pins, OEM 8.1L/NV4500 flywheel and a 10 spline clutch disc to fit my transmission's input.

You can use any GM NV4500 bellhousing and an 85-91 square body hydraulic clutch and master to operate either the internal or external slave depending on what year of NV4500 you run. You'll need to make your own hose to connect the two, but the aftermarket has all the fittings needed to put a -3 AN hose between the two. Of course you'll need a high hump transmission tunnel to clear the transmission. You will also need to update the tuning on the engine to suit as well.
thanks

I'm starting to really think about doing this swap (along with a front D60) and my concern is the part you said about the 'high hump transmission tunnel'. My truck is a 75 GMC c35 2wd dually that I swapped an 8.1 into a few years ago mated to a gear start 4l80e. Well this mountain that I live on did what the old timers always said it would do: it ate my auto tranny. Been getting a P0894 now for a couple of years. The truck is ONLY used to haul materials and water up here (22" GN with 850 gallons).

I have a J10 with AMC 360/nv4500/atlas 4spd and I really like the nv4500.

I need to educate myself on the tranny hump. Hope that won't be a show stopper to convert my old square.
 
thanks

I'm starting to really think about doing this swap (along with a front D60) and my concern is the part you said about the 'high hump transmission tunnel'. My truck is a 75 GMC c35 2wd dually that I swapped an 8.1 into a few years ago mated to a gear start 4l80e. Well this mountain that I live on did what the old timers always said it would do: it ate my auto tranny. Been getting a P0894 now for a couple of years. The truck is ONLY used to haul materials and water up here (22" GN with 850 gallons).

I have a J10 with AMC 360/nv4500/atlas 4spd and I really like the nv4500.

I need to educate myself on the tranny hump. Hope that won't be a show stopper to convert my old square.
It bolts in.
 
I have a buddy with a '98 chevy 3500 with 6.2 diesel and nv4500. he will give the nv4500 to me for free. I wonder if that bellhousing will work for ? I don't know anything about those chevy diesels.
 
I have a buddy with a '98 chevy 3500 with 6.2 diesel and nv4500. he will give the nv4500 to me for free. I wonder if that bellhousing will work for ? I don't know anything about those chevy diesels.
Same bell as SBC/BBC .
This thread has a lot of info on 8.1 Hope yall do not mind.

 
Finally got around to play with the scanner. This Autel is badass.

Confirmed my wheel speed sensor was bad (you can see the data stream drop on the graph). I swapped it around and the problem followed the sensor. I tried to clean the UBs since I saw that rust may be a factor in this, but no dice.

Ordered new Timken UBs and sensors and will install next week.

That said, I think there is another issue with the brake system that's keeping the ft right dragging. Even with the fuse unplugged (no ABS at all) the brakes drag after a few minutes of driving.
 

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Finally got around to play with the scanner. This Autel is badass.

Confirmed my wheel speed sensor was bad (you can see the data stream drop on the graph). I swapped it around and the problem followed the sensor. I tried to clean the UBs since I saw that rust may be a factor in this, but no dice.

Ordered new Timken UBs and sensors and will install next week.

That said, I think there is another issue with the brake system that's keeping the ft right dragging. Even with the fuse unplugged (no ABS at all) the brakes drag after a few minutes of driving.
Could you remove brake assy, apply brake synthetic(hi temp) grease to mount parts. I know they can get stick and drag. Clean and specific grease will help out.
 
Could you remove brake assy, apply brake synthetic(hi temp) grease to mount parts. I know they can get stick and drag. Clean and specific grease will help out.
Already did.
No help unfortunately.
 
Direct swap to 145 amp alternator upgrade.

I used this one PURE ENERGY 8292603N
Might as well improve power cabling and grounds while you are in there. If you are unfamiliar google "big three upgrade"
 
Already did.
No help unfortunately.
Are the rubber lines original? They can collapse on the inside and hold pressure not releasing very quickly. Theyll release or bleed down over a bit of time making them free at startup and drag while driving.
 
Are the rubber lines original? They can collapse on the inside and hold pressure not releasing very quickly. Theyll release or bleed down over a bit of time making them free at startup and drag while driving.
Thanks for checking in.
The rubber lines is the first thing I changed.

I haven't driven the car since December. I need to fuck with it more but since my buggy is down and I don't need to tow, it's sitting.
 
Quick update on my pile, finished last round of parts replacement and took it on its first long trip. Bud of mine welded in new patches to repair the slight rust damage in the rockers last fall. Most recently new steering box (again, original reman had a dead spot and slop in the input shaft), new set of 275 bfgs on a set of methods I picked up, also turned the torsion bars up about an inch or so and replaced the body mounts. Took it on a 500 mile trip last weekend and averaged ~12 mpg (hand calculated) with the cruise set at 63. Only thing left to do now is bolt on the new steps after I undercoat it, and find somebody to do the headliner. New wheels and tires can make anything look better. :smokin:


279912995_10160455570852033_4062984633236040450_n.jpg
 
If anyone here is like me and has a WorkHorse chassis RV, there are a lot of interchangeable parts for the 2500 8.1, with the 2500 parts being 200% less in cost. Includes most engine parts. I also found a bunch of parts that come off of other GM models for dash and steering column controls. A WorkHorse multi-stalk turn signal switch is several hundred dollars, but it's the same part that GM used in various models for about a decade, which you can get aftermarket for under $30.00.

Need to get creative with a 20-year-old Class A coach if you want to keep it, and I have no reason to get anything else. Mine will outpull most of the newer V10 Fords. It outpulls my last Ford chassis RV that was 7,000 pounds lighter and 3 years newer.
 
Got my 8.1 tuned by Barnyard Garage

Can't wait to tow with it. It'll take getting used to driving with new tune and different shift point.

To think most people wanted their 8.1 tuned to the max, very glad Tuner was in person so would accommodate to my preference.

Surprised how much power came out of it with just my preference.

I might have transmission sensor relate that needs to be replacing. I'll be looking into it to ensure all is good and how I like it while towing before I would get tune re-adjusted if needed.

Awesome guy, would recommend.

What's only done to truck
180* Tstat (reduce oil consumption but drop 1 mpg)
Aftermarket intake instead of stock box. I'll plan getting stock air intake box and cut it open a bit.

My next mod will be getting another TB and send to shop for TB Bore and ceramic coat stock header(after fire season) I'm looking into learning how to make my own big 3 wire build.
 
I wasn't sure if excessive oil consumption was good thing. I average 3 to 4 quart of oil before my 3k oil change.

It's only 1 quart of oil per oil change since 180* installed.
Isn’t the oil going to be cheaper than the fuel loss?

I like always having bright yellow oil.
 
Any idea if the 8.1L is available as a GM crate engine ?
 
Yikes Ok sounds like you did the right thing.

I wasn't sure if excessive oil consumption was good thing. I average 3 to 4 quart of oil before my 3k oil change.

It's only 1 quart of oil per oil change since 180* installed.
 
Mark IV BBC also arent available but lots of parts are, finding a good core block cost me a ton of cash.


Not last time I looked. It's been discontinued for over 10 years. :laughing:


It was a great motor with poor marketing.
 
Yikes Ok sounds like you did the right thing.
I'll definitely love to do the PCV mod, just have to look more into it as information seems a bit vague.

What's the normal oil consumption on the 8.1?
 
Mark IV BBC also arent available but lots of parts are, finding a good core block cost me a ton of cash.

Yeah. There's lots of low mile 8.1's out there in motorhomes ready for the picking. Get to it :flipoff2:
 
Thanks for checking in.
The rubber lines is the first thing I changed.

I haven't driven the car since December. I need to fuck with it more but since my buggy is down and I don't need to tow, it's sitting.
Did you ever get the brake issue fixed? I was having the same issue on my burb. I dont know if it has the same calipers as the trucks. Cleaned the pins and replaced the rubber socket in the mount and replaced the boots last fall. Heading back east last month about 100 miles from home and I hear some light grindage. Brakes were dragging again not even 5k miles since replacement. Turns out when I set the new boots in the socket I split the rubber. The little rubber socket was getting crudded up and the pins was rrusting and sticking. So I got new pins boots and sockets. Dug out the rubber socket ran a .410 wire brush down in the bore pput in the new rubber and greased em up. Pressed the boots and I ripped them again. Fucking garbage the metal piece is a few red **** hairs bigger than the socket. Yes I cleaned it out then took a scotch puff on the dremel and really cleaned em up. Still have to press em in.

How the fuck do you do this without ripping the rubber? I used a piece of pipe which just fit over the rubber and set on the metal but the metal cup squished the rubber and ripped it when I pressed it in.
 
It still have a light drag but I'm driving it as is.

New calipers, mounts and lines, new unit bearings and ABS sensors.

I have to have some kind of an issue with the passenger side wiring or the ABS computer since it keeps throwing codes for lost com with the pass side ABS sensor.

I don't drive it enough that it bothers me but it's a little aggravating.
 
NO its not.

There are two nv4500 bellhousings 92-94/95 and 96+.

Different transmission bolts and different bearing retainer pilot hole in bellhousing also.

Early is 5.125 late is 5.600, trying to mix and match is a bitch.

The only thing thats the same is the engine bolt pattern as to the 6 standard bolts, the 12 o clock bolt hole unknown.

Same bell as SBC/BBC .
This thread has a lot of info on 8.1 Hope yall do not mind.

 
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