A-833/NP440/MY6 transmission on a BOP bellhousing?

[spidereyes455]

I actually have one of those laying around in my storage garage, it's the gm pattern aluminum case o/d version as well. I had it in my GP when I first did the manual swap. The ratios were actually nice with the 400 sbc and the 4.11 rear that were in the car at the time. I wound up taking it out and swapping it out for a Saginaw 4 speed only because it was leaking oil from the front , probably the input shaft seal. I didn't have access to a lathe at the time so I wound up turning down the front retainer on a bench grinder but I got it to fit. Its been laying around ever since.

 

[Bonnewagon]

Want to sell it? PM sent.

 

[spidereyes455]

Want to sell it? PM sent.

PM replied.

 

[Bonnewagon]

UPDATE: I got it! Road trip from Shitty City to God's Country in NE Pennsylvania. It took an hour to crawl across the $#@^%& Bronx! Turns out Jim is a great guy and the transmission was exactly as he described it. Now to figure out how it ticks and change the seals. It will go either in the Bonnewagon or my '68 Firebird. Tough decision!

 

[olds307 and 403]

I would so like to find a cast iron 2wd version with the GM pattern.

 

[Bonnewagon]

My research indicates that when GM took the trans from Mopar they all were aluminum cases. Early models had the GM bolt pattern but later models had the Mopar pattern. I don't know why unless it is because Mopar still used them in trucks and vans. The later GM bell housing was Chevy block only but had the dual trans mounting pattern. That is why I needed the early GM only pattern so I could use it on a BOP bell housing. The one I got from Jim has the forward mounted shifter which is the 2wd version and it places the shifter in about the same place as the Saginaw does for our cars.

4WD Shift Plate on Left. 2WD Shift Plate on Right.

 

[olds307 and 403]

My research shows the aluminum version is much less desirable for big torque, according to Mopar guys, flexing issues. They probably only did so many GM only castings and ran out. I wonder if all the GM guts with GM spline counts could be swapped into a Mopar iron case. But it would present the same issue, no BOP pattern which is an issue for me as well.

 

[Mike P]

Been following this thread for a while, some good information!

A few years back I was hunting for the Chevy version of the 833 but didn't have any luck finding one. I do have some experience with the Mopar version however and am currently running one in my 57 Plymouth behind a 354 Hemi with 4.10 gears.....vehicle weight is probably around 35-3600 pounds.

In the mid-late 70s both Chrysler and Ford both played with 3+OD transmissions in the quest for better fuel mileage and converting existing 4 speed tooling to do this was the quickest way to get there. The biggest complaint was/is generally the less than optimum gear splits for any type of spirited driving.

Back in the days of the national 55 MPH speed limit these transmissions were generally put in front of rear ends with relatively high gearing (3.00 to 3.50 range) and fairly low output engines. In the case of the Mopar A833 OD the transmission uses relatively deep 1st gear (3.09 if memory serves correctly). It's great for getting a heavy car without a lot of bottom end torque moving under normal conditions but with 4.10 gears it winds up being almost too quick to be useful for really launching the car (I've hit the rev limiter more than once in low gear). The 1-2 gear split isn't too bad but the 2-3 split is pretty wide. A lot of people who drive with these transmissions really wish they had 1 more gear on a lot of occasions. All that being said they are still fun to drive and do make a decent reliable transmission.

In my experience there are 2 or 3 weak points on the 833 ODs. The first and most major one is the aluminum case. They crack especially when used behind anything with significant torque and aggressive shifting. Although they are a little harder to find, I would defiantly hold out for a cast iron case version (which I have in the 57) or keep in mind that the aluminum case is not indestructible if running one of those.

Although I've never run in to it, on the aluminum case 833 ODs the counter shaft is a floating design. Some people have reported wear in the case because of this resulting in oil leakage. It can be repaired by boring and bushing the case, but is another reason I tend to shy away from the aluminum version of this transmission.

On a normal non OD A833 4 speed the input and main shaft are locked together in 4th gear. On the OD version of the main shaft is spinning faster than the input shaft in OD and over time can result in significant wear on the bearing end of the main shaft where it fits into the rollers on the input shaft. Pretty much something to look for when you tear one down.

Back in the late 60s when I was working in a Chrysler Plymouth dealership there was a service bulletin regarding the use of ATF in the A833s. If the transmission shifted hard (and especially in cold weather) it was recommended that a pint to a pint and 1/2 of the 80-90 weight be pulled out and replaced with ATF to thin the lube. It worked well on hard shifting transmissions, but from personal experience if you have worn synchronizers (grinding when up or down shifting) it will only aggravate the situation.

 

[DRIVEN]

I mentioned in an earlier post that I tried different fluids but found that GM Synchromesh worked the best for me. It's a little pricey but you only need a couple quarts. https://www.amazon.com/dp/B0026JK8FA/?tag=gbody-20

I've kind of been considering selling all mine. I don't drive my El Camino on long freeway trips anymore so the Muncie could go back in. My '35 has a pretty cramped cab and a transmission with a traditional shifter basically rides my right calf. A TKO600 with forward position shifter would really be nice.

 

[Bonnewagon]

I have read about the case wear issues as well and the fluid opinions. I guess it would behoove me to take it apart and look for problems BEFORE I put it in a running vehicle. So what was the factory lube? 90 weight? Or ATF? I had a Sunfire with a 5 speed Getrag and I stupidly used 90 weight in it. I then had gear clash because it made for an extended spin down time. The Synchromesh cured that. Most complaints I have read about involved racing or performance driving. That is not my plan. I want a big motor like a 400 or 455 that I can use on long trips without gassing up every hour. My old '67 Borg Warner T-16 3 speed was a great street transmission but it really needed OD for distance. I currently have a Pontiac 455 in my '68 Firebird. I have the same BW ST-10 4 speed with the 3:42 first gear and a 3:08 rear end gear that I had in my '77 TA. While the 3:08 rear made for easy highway cruising, the 4 speed felt like each gear was out of breath too soon. I often skipped a gear just because I could. With the 3 speed you were really needing the next gear and I am hoping to get that same feeling with this trans plus the OD.