NP833 O.D. problems, who has had them

I've been putting together a street car, 1966 Dodge Coronet Deluxe 2 door sedan that I installed a NP833 tranny, 440 motor and a cut down Dana 60 with 3.55 gears in it.
I took the tranny completely apart to inspect it as I bought it out of a local towing and scrap yard, I didn't find any real problems in it but I was amazed on how small the O.D. gear is on the cluster shaft.
My questions are who has had problems with them or broken one on the street? What problems did you have and do you know what parts broke?
Thanks: Cab

Cab there are some guys that have them in street cars that hold up fine unless you whoop on it with good traction. The gears do look pretty wimpy even compared to 23 spline gears. I would put one in a easy driving B-body and even if you do break it parts are plentiful and cheap

Gus

I have installed several of them in our dinosaurs over the years and have had good luck with them. But they won't take a beating. As long as there is limited traction and not much gear banging, they work real well with deeper gear ratios. With taller rear gears, the tranny's gear spread starts to show up.

I put one in this, behind a nice 360 and in front of 3.55 gears but it didn't stand up to towing duty very long.

The real problem is wear on the countershaft, as it uses thrust washers, not tapered bearings, and has no center support between input and output shaft, like a modern trans, so they get loose with big power or towing in overdrive. Use gear oil, change it often, don't beat on it in overdrive, and it will last a long time. Start with new thrust washers, bearings, needles, countershaft pin, and shim any excess endplay out of the cluster gear and run it. Just remember it was designed for a light 6cyl car so.... one last thing, check the ends of the cluster, may be worn from thrust, or wiped washers and metal.

I guess it depends,there are a few in 426 Hemi street cars in my neighborhood and a few in 440 6 pack cars used for street and cruising, and they hold up pretty well. They are put in cast cases though. Did one for my car from a Truck version, though it is not installed yet.

When you say countershaft are you saying the cluster gear shaft or the output shaft?

The shaft or pin inside the cluster gear, it gets grooves in it where needles ride, end of cluster also gets wear on some.

i had hemi 4sp changed 3 years ago . never looked back.

You are bringing up a lot of bad memories cab, you should also check the front of the case where the countershaft pin rides, if it has a flat plug there it has a floating pin, you might want to bush that and make the pin tight. I think the cast iron overdrives were not floating pin, could be wrong, been a while.

I've seen 2 of them from behind Slant 6's that looked like a grenade went off inside them. I personally would never use one!

i was going to say that i use a Passon 4sp overdrive.

The OP asked for experiences. And he has gotten enough and they have been consistent enough to draw a reasonable conclusion. But an expressed opinion without that experience is really just a guess. And not a good source for advice.

I had one in a '77 Volare with the 318 that I bought brand new. The comment about being a PITA with deep rear end gears is correct. IIRC, the rear end was a 3.21 limited slip and you were in 1st gear only long enough to say you had been there. After I had about 40,000 miles on it, it developed a nasty trick of sticking in fourth gear if you hit it hard. Never did discover what was happening. Went through the shifter linkage adjustment and a side cover inspection but never discovered the cause. I really like the car though. If I was younger I'd probably be looking for a Roadrunner version.

I had a 77 Aspen RT with the 318 and the 833 OD. That car got beat on pretty well and the trans held up until it had 95,000 miles and then it got stuck in second or third gear. My dad took it into his machine shop at work and they corrected whatever was wrong with it without buying parts.
I recently had a guy tell me he had one in a 440 Challenger that would lift the left front tire and it lived in that application.

I've got one to put in my 73 Cuda and as long as I can live with the ratio spread I'll keep it. I can't afford a Passon or Magnum swap.

I have one in my 47 desoto with a roller 318 w/ cross ram 2x4 and has 323 rear gears. I rebuilt the trans when built the car. I didn’t see anything wrong with it inside and it hasn’t given me any trouble. The gear spread doesn’t bother me at all but I’m not racing it either, it’s just a fun cruiser.

The aluminum case OD do have the floating cluster shaft and wear easier. Cast Iron case do not have a floating shaft. First gear is a very low gear at 3.09, hence no need to even use it with a big block. The only real difference if put in a cast case, is the main shaft is thinner for at least one of the gears. So if anything was going to break it would that in my opinion. This is not a setup for track car, but inexpensive option for a cruise OD car.

I have a 383 4 spd B body that has a dana with 3.54. The motor trans are stock set up. I hardly use first gear even with a stock 383/4 spd.

With the over drive, I would expect it to be two speed with overdrive. But if you wanted to pull a cool hole shot in first gear, what a ratio with a 3.54.....

Teaching my son to drive in a 51 Plymouth with a three on the tree.

Going to put in an A833OD I have on the shelf, that 3.09 first gear will really help him taking off, lol.

I don't pull hole shots or tow so the A833OD works fine for me, I probably have close to 200k miles on the two I have.

As for the aluminum case counter shaft hole issue, it can be bushed to fix that. I believe both Passon and Brewer's offer that service or did.

https://www.hotrod.com/articles/mopp-0110-a-833-aluminum-case-buildup/

I would have to see that with my own eyes to believe it.

Not everyone knows how to shift properly...

Years ago, a buddy put one in his hemi 4spd Bird, along with 8 3/4 rear end . . . he drove it that way for YEARS !!! Yes, he kept the original parts, but wanted to drive his car, all over !! Was cool to see real hemi 4spd Bird out on the highways !! . . . I had a 76 Road Runner, original non touched car, 57k miles on it when I got it. 318 with 4spd OD . . . had Passon rebuild the tranny, mainly for the leaking seals, but hey, might as well get it totally looked after. It was cast case, but drove that car all over, and put 21k miles on it ! Ran great, 23mpg all day long at 70mph ! . . . totally cool RR with the superpak option (all the spoilers, window louvers and stripes) . . .

They probably belonged to Slantzilla

Decided to go back an examine in more detail the part difference. Picture of the OD(gears on) and normal Main shaft (no gears). Basically the 2 shaft are identical from the flange back towards the tail. Same size, same hub and slider for 1st and second gear.

What is smaller is the front of the shaft because the new 3rd gear for overdrive is now the smaller OD 4th gear. That small gear required a reduction in shaft diameter. Smaller hub too. Regardless, the shaft is not the issue anyway. The weak link would be the teeth on the shaft and hub that transmit the torque. The teeth on the hub and gears that lock in place when the slider engages. So where things are smaller is direct drive (3rd) and OD (4th). But no where near any limit that you would break the hub, or gear, let alone a main shaft.

The cluster is the same. So if you move this into a cast case, or have OD with cast case you have a transmission just as strong as any other 23 spline.

If you compared it to a slick shift Hemi, it may even be stronger then that. While hemi had a bigger input shaft, the back end is the same as 23 spline other that bushed gears and bigger bearings. Slick shift removed every other engagement tooth on the gear and hub from 36 to 18. That actually weakened the gears. Requiring more frequent repairs, until liberty made their mod with longer and wider teeth.

Aluminum cases are a whole other thing though. As discussed the floating counter shaft and weaker aluminum case could round out causing reduced gear mesh, riding tip of tooth to tip of tooth, with greater back lash, that just gets progressively worse if abused.

When I did this conversion a few years ago, I used later model big bearing cast cases, and over drives from truck set ups that had the longer B/E body shaft and tails.

You could do the same with an A body, but need the A body OD.

I have OD guts in an iron case in my 68 Charger/440 engine. Did the swap over 10 years ago but not tons of miles on it. (with 4.10 gears the miles are more pleasant) At the time I rebuilt the trans the reading I'd done said the aluminum case allowed the countershaft to move away from the mainshaft and that's what did the damage. The article I read talked about machining the aluminum case to spread the load. Its been a really long time and I cant remember the details. In an iron case with street tires and reasonable driving I wouldn't worry about it.

This article goes through the steps of bushing the aluminum case counter-shaft holes. Not a terrible job if you have a mill. No idea how much a shop would charge you but figure a couple hours on the mill and the lathe work to turn up the bushings. I plan to do this to the one I have.

https://www.hotrod.com/articles/mopp-0110-a-833-aluminum-case-buildup/


Does anyone know how much weight is saved by the aluminum case?