I am looking to install a NP-833 4 speed overdrive transmission in my 48 Buick in place of the stock 3 speed. I have found the needed adapters and have changed the rear end to an open drive line set up. The transmission I have found has a cast iron main case, aluminum side cover and aluminum tail shaft casing. The main case has a casting number of C15453 and the tail shaft a casting number of C15402 2. It is supposedly out of a 1982 C-10 Chevy 2wd pickup. It has a New Process logo on the case and looks just like the all aluminum version. I have been told that the over drive transmission with the 1:.73 4th gear I am looking for is all aluminum. What is the truth? Please let me know. Thank you in advance!!!
I have a GM NP833 overdrive, but I can't tell you about aluminum vs. cast iron cases because my trans is in a shed that is all snowed in so I can't go look at it. But I can tell you this to help you ID your trans: The NP-833 actually uses "3rd gear" as the over drive, and "4th gear: is still 1:1 direct drive. Thus the 3-4 shift arm, (the front one) is flopped upside down. (pointing down) So when you put the shifter in the 3rd gear position, the trans is actually going into 4th. Then when you put the shifter in 4th, the trans is going into 3rd. If your trans has the front shift arm pointing down and the middle arm pointing up, it is probably an overdrive. If the arms are missing, or you are unsure of their original position, rotate the front arm clockwise to put the trans in 3rd gear. Turn the input shaft one revolution and see if the output shaft turns more than one revolution. If so you have an overdrive. If it has a GM bolt pattern on the front, then it is obviously a GM, not a Mopar. I hope this helps, good luck.
Hemi Joel, There WAS a New Process 3-speed w/OD transmission with the GM bolt pattern on the front and I have one. It is definitely overdrive. I also have one with the MOPAR front pattern. It used a special aluminum bell housing made by GM with MOPAR front bolt pattern and Chevy transmission bolt pattern.
Gm used the np833 overdrive trans in 1/2 ton trucks. If it has a 10 spline 1 1/8 input shaft its a GM box, Chrysler used 23 spline and 18 spline input shafts. All GM 833s were overdrive boxes.
I have seen the OD transmissions with a cast iron case used in Dodge 1/2 ton pickups and vans. I have one that is all cast iron and is definitely OD. The all-aluminum OD transmissions were used more in the F-body cars (Aspen/Volare). They have the shorter tailhousing and the shifter mounted more in the middle of the tailhousing. All MoPar application A-833 OD transmissions were 23 spline input. No OD A-833's were built with an 18 spline input shaft - that is the 'hemi' 4-speed. I thought the GM version of the OD A-833 was all aluminum as well. It had different case and tailhousing as well as input and output shafts to keep it interchangeable with GM stuff (bolt patterns as well as spline counts). I did not know that there was a GM bellhousing with a MoPar pattern. Was it iron or aluminum? The previously stated information regarding the inverted 3-4 shift lever (points down instead of up like the rear 1-2 lever) is the easiest way to identify an OD A833. If the lever is missing, rotate the shaft where the 3-4 lever would be counterclockwise all of the way and compare the speed output shaft when spinning the input shaft - an OD trans output shaft will turn more revolutions than the input shaft (thus, OD). Finally, you can pull the side cover - an OD trans has a much smaller gear right behind the input gear.
"I did not know that there was a GM bellhousing with a MoPar pattern. Was it iron or aluminum?" The one I have is aluminum. The bell & transmission came out of a 1985 Chevy 1/2T with a 305 V8 engine. The transmission was Chevrolet option MY6 in the truck.
ok, i too have one of these transmissions....i will post a pic or to also - cast iron cas, alum side cover, alum tailshaft...came with a hurst shifter, but one of the arms was cobbled....course input shaft, fine output shaft - of course, there is no shifting arm ...case number C-15453...m086181 & cc1132321 on the side machined surface - numbers are as best i could tell...much larger case than a muncie - bottom of th main case has 4-5 ribs cast into the case...tailshaft is C-154201 side cover c13550...it was in a small block powered 1/2 ton chevy pickup, but i could not get the bellhousing - this bolt pattern is weird - definitely NOT a standard GM pattern like the muncie...exact same length as my M20......3 spd w/od ?...4 spd?.....is it worth anything?...strong?...man it is heavy duty...well, heavy anyway...help!....johnnyB
We have used a few of these over the past coupel years. The NP833 is a pretty good workhorse, after all they put them on the full size chevy trucks through the late 80's. I have one in my 55 chevy truck. And yes the bolt pattern is very different than the normal gm..You need a very specific bell housing, you can find them on ebay for around 250 or so...Also be careful with the bearing retainer in the front they do break kinda easily..I know...I have broken them and they are extremely hard to find, and useless without them...The trans itself is worth about 75 -100 without the shifter and connecting rods, as long as everything spins nice. Those connecting rods are bent specifically for the trans itself and not easy to come by either...
I have one of both and was told the iron case came from behind the chevy diesels and had the mopar bolt pattern with a special chev bellhousing
The bearing retainer plate is the same as Mopar 833. There are two different cases: one with a GM mounting pattern, one with the hybrid shown on the iron case version posted above. The GM-patterned case will bolt to a standard GM bellhousing, if you turn the O.D. of the bearing retainer down a quarter inch and use socket head bolts to reattach the bearing retainer to the trans. The shifter mechanism itself is also unique to the trans, not just the shift linkage rods. I've compared them side-by-side to the Mopar 833, and the shifter mechanism's fingers that come out the bottom are unique. I'd heard about the iron-case version, but hadn't seen one yet. The Mopar crowd has found the aluminum case to be a weak link: the counter shaft starts to wallow out the bore in the case, and then things go bad. -Brad
I have the GM iron case one, with specific aluminum bellhousing. There are holes in bellhousing for a regular GM bolt pattern as well. I was told it came out of van, and has rear mount shifter with tall, straight shift handle. The trans mount is cast into tailhousing right at the rear seal area. I haven't installed it yet, but plan to build shifter to put it more towards front and center, for my 34 project. If anyone has pictures of their modified shifter, I'd appreciate it. (PM or email)
It's a bayonet-style shift handle--you should be able to find a different handle to put in the shifter mechanism body. I swapped a different one into the one I put in my '61 Suburban. -Brad
I have an aluminum case GM verison of the A-833. I thought about using it in a 1965 Chevy 1/2 ton truck to replace the granny 4 speed. The bellhousing casting # is 3925505 which I believe was used in 1968-1972 Chevy trucks. The trans lines up to the GM bell, the bearing retainer fits the large diameter bell without any modifications. Any one out there used this bellhousing to convert granny tranny in the 1960-1972 Chevy trucks? The down side is the tranny has the shifter linkage but no shifter. Any ideas what would work for a shifter? Any problems I might encounter?
I know this is an old thread, but since there is not much info about these transmissions I'll add what I can. I have put one in my '50 chevy truck it's an 80's truck, aluminum case type. I got a good deal on it and all of the parts were included except the bellhousing. I haven't driven it yet, so I'm not putting much stock in it. In fact I have a TH350 as backup but if this works...hey 4 speed and O/D for cheap? I'm in. I managed to mate this up to a 5.3L which took quite a bit of research but it worked out beautifully. Not the most traditional drivetrain but I'm doing my best to at least make it look that way. My trans has the very weird bellhousing that is in fact half mopar / half gm. I looked them up on car-part.com and found a great salvage yard owner who had one and shipped it to me for $50. Here are a couple of pics:
Leevon, Nice clean setup. What is the part number on the Hurst shifter? I have the linkage but no shifter. Thanks
I put one in my '50 GMC - with 3.73 gears it cruises at around 1900 rpm at 60 mph behind my 270 inline. Adapted the column shifter to get 4-on-the-tree - works slick! Reverse is done with a Morse push/pull cable from a handle under the dash Its a little busy under there, but you do what it takes . . .
Motion Guru, That's so cool, 4 at the tree. I also like the cable actuated reverse. That's even kind of a theft deterrent device. A true Mystery Shifter. Leave it in reverse and if the car thief doesn't know how to get it out of reverse real quickly, he'll probably look for another target. Great job
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