A833 transmission for my flathead

[Tony_Urwin]

I hate the 3 speed crashbox behind the flathead in my 1948 B1C. So I bought a A833 on eBay and the adapter plate from George Asche. I dropped the old transmission from my truck and now I have questions for the more experienced mechanics on the forum.

 

I guess I should request that we please keep our posts on topic. Previous discussions of the A833 swap were derailed by forum members with opinions on T5 swaps or members who think it's blasphemy to alter an original truck. As a result of the bickering, those threads about A833 swaps were either closed by the moderators, or else the posts were deleted by PO'd truck owners. Not much help there. So please, honest opinions of the process, honest answers to questions, or else ignore the topic.

 

The transmission arrived, 23 spline input shaft, long tailpiece version with dual shifter mounts. Hurst shifter on the rear mounting location. The seller told me that the transmission had been rebuilt by Brewer Performance here in Ohio, so I took a trip to Laura, Ohio to visit Dan Brewer. He told me that the plates in the Hurst shifter mechanism were not correct for the forward location and rebuilt it while I waited. The Input Bearing Retainer was smaller than the hole in the AoK adapter plate, but Dan had the correct size (5.125") retainer, as well as a slip yoke I needed and all new bolts, clips, and shift linkage that fit the forward shift location. Dan gave me $250 for the bell housing/long shift linkage from the eBay auction and I walked away with the parts I needed for $12.

Now that I had the slip yoke, I could turn the output shaft and count the revolutions on the input shaft. It looks like I have the close-ratio version of the A833 transmission.

• 2.47, 1.77, 1.34, 1.00 I'm happy with the non-overdrive version final ratio, since I have a 3.55 Jeep Cherokee rear axle. But is the first gear too high for my flathead? I read that the stock transmission had a 2.57 first gear. Is that correct?

Next I measured the input shaft on the stock transmission. The splines extend to 5.5" from the transmission face and the shaft is 7.5" long. The splines on the input shaft of the A833 extend 6" from the transmission face and the shaft is about 8.25" long. The adapter plate is about .375" thick, so we can subtract that.

• Will the slightly longer splines and input shaft be an issue?

Help me out here, guys. I'm having a hip replacement on November 12th, and I'd like to get this done. I'm off to Harbor Freight to buy a cheap transmission jack. That transmission weighs 125 lbs!

 

 

 

 

 

 

 

 

 

[Dave72dt]

My suggestion would be to bolt the adapter plate on, grab your tape measure and measure the distance between the trans side of the disc splines to the face of the adapter plate.  That will tell you the disc will end on the input shaft on the A833. Slide the tape through the splines on the disc to the front edge of the splines and measure again to the adapter face.  This will tell you where the disc will ride on the A833.  Once again slide the tape through to find the edge of the pilot bearing.  That will give you the location the pilot begins on the A833.  One more time all the way in (you may need a rod for this one), will tell you if you need to trim the pilot section of the input shaft. Tthose measurements should give you a visual layout.  Compare you shaft diameters at all pertinent sections as well.

 

[Plymouthy Adams]

Sounds like Mr. Brewer corrected all thing on the transmission that was an obstacle and, on the spot, and fairly priced....the length of the input shaft will need be addressed and likely a shortcoming of the supplier of the adapter it would seem.  Looking like a spacer would need be machined for the front of the transmission and adapter.   Typically, I think they are more concerned with the later 833 with the OD gearing in their fabrication which is the larger cover and different input shaft (?).   I have the OD 833 here on hand but have never measured any physical feature to verify just what would be the difference between it and the one you have.  The answers would likely need to come from the AOK boys who sold you an adapter and may be best directed back at them instead of here.  You almost there. to prevent chatter your spacer will need be true in thickness...likely a milled/ground surface.

 

As an added, am I correct you did not notice the length difference till after your trip to see Mr Brewer, they have all the different input shafts on hand and he could well advise I would think with a phone call as to what input shaft you may need and or if there is a difference in overall length.  I know the one I placed in a setup many years ago had the pilot bearing length trimmed down to allow it to snug up....could be an option here. 

Edited October 30 by Plymouthy Adams

[Tony_Urwin]

The AoK adapter is really designed for the 1976-87 A833 transmissions I guess. Those overdrive transmission had the aluminum housing and a input bearing retainer with the 5.125" base. That part is not really a problem for me, since the different bearing retainers all swap. I guess I'll find out if the extra length of the input shaft is a concern by test-fitting it. I would hate to have to cut any off of the shaft, but we'll see.

 

And, no, I did not even measure the length of the original input shaft, I just trusted that the AoK adapter swap was possible.  I don't think the A833 shaft come in different lengths. Since a lot of the discussion posts about the A833 were deleted here, I feel like I am starting from scratch to some degree.

[Plymouthy Adams]

Still think a quick call to Mr Brewer would be in your best interest as to length...be sure to let him know the adapter was based on the aluminum body and that you have the cast iron behemoth.  My experience denoted that there may well be in put differences just I cannot say what they are...glean these facts from Mr. Brewer as I think he would be the best man in the business for the differences should there be any.  You have very little to lose with the phone call and possibly everything to gain.  

[Plymouthy Adams]

it was 35 years ago I last worked an 833 install....what my reading back on the subject concludes is the depth of the bore of the crank for the pilot bushing and added headspace for the total length of the input shaft.  Most come into this problem with affixing a manual to a automatic crank.  It this case, it is a dissimilar size of components from one era to the next.   In the scheme of things most bore the depth of the crank or cut the additional ~.500 inch off the input shaft.  This depends on what you have to do the work with in as much as tooling.    Seems in factory setup, the shaft protrudes approx .500 beyond the pilot bushing into the crank counterbore this if cut, would not affect the overall use of the transmission stock or custom install.

[Tony_Urwin]

I checked the fit on the AoK adapter yesterday.  The center hole is a few thousandths too small to fit over the input bearing retainer. 20 minutes with a file and some emery paper and I was able to pass my new bearing retainer through the adapter. The picture shows the adapter bolted to the transmission with the old, smaller bearing retainer. Next I bolted the adapter to the truck bell housing. The bolts aren't quite flush with the adapter plate, but close enough, I guess.

[Tony_Urwin]

The top two holes to attach the transmission are threaded, the bottom two are not threaded and will need nuts and lock washers.  I plan to cut some threaded rod to use as a guide when I install this monster.

Edited October 31 by Tony_Urwin

[kencombs]

The recessed head bolts must be flush or below the adapter surface.  Otherwise the transmission mounting bolt ‘ears’ will be stressed and may crack.   Yours is the second case of those holes not being deep enough that I’ve read about.  

 

 

 

[Tony_Urwin]

That's a good point. I also read that another member had to file the center hole as well. I was able to file the center easily enough, but I wondered about making it slightly off center. That's probably not a problem, but reaming out the recessed bolt holes will be more difficult. Maybe clean them up with a dremel?

[Tony_Urwin]

I'll see how close to flush I can get those bolts. Maybe fender washers under the ears would relieve the stress. The bolts they send are anodized, right?  Should I use anti-seize on them?

 

By the way, I miked the input shafts last night.  They are both 3/4".

Edited November 1 by Tony_Urwin

[QEC]

Perhaps a fender washer would work for what you are doing. A better choice would be to buy a countersink if only for this one job. Yes, the manufacturer should physically check that particular fitment before ever sending it out the door as it would be an easy correction.

The thickness of the fender washer will reduce the engagement of the bearing retainer by that amount. I would also suggest that you check the adapter centerline against the crank. The front bearing does not like parallel mis-alignment.

[Los_Control]

$10 on Amazon

[John-T-53]

On 10/29/2024 at 8:50 PM, Tony_Urwin said:

• 2.47, 1.77, 1.34, 1.00 I'm happy with the non-overdrive version final ratio, since I have a 3.55 Jeep Cherokee rear axle. But is the first gear too high for my flathead? I read that the stock transmission had a 2.57 first gear. Is that correct?

 

I hate to tell you, but if you are placing this behind a flat 6, too high. Your first gear will have an overall ratio of 8.77, so low performance and no "get up and go".

 

8.16 is second gear in my truck, for comparison. You want to be in the area of 12-13:1 for first gear.

 

I'd suggest changing the gearset, if possible, or finding a transmission with a desirable set of gears, otherwise your project will have an undesirable outcome, and may lead to more fallout in the decade long battle between the transmission swap clans on this site. 

[Tony_Urwin]

I was afraid of this, John. I don't know the gear ratio for sure. I bought a slip yoke from Brewers Performance, inserted it in the output of the transmission, and turned it without having any of the shift linkage connected. I put masking tape on the input shaft and marked the tape with a sharpie. After several attempts, I consistently got 2.55:1, which is not even a real possibility. More likely is the 2.47 you suggested, with the final ratio of 8.77 in first gear. Another possibility would be the 2.66 first gear, which would give me a slightly better final ratio of 9.44. Best would be the 3.09 gear, like the first gear in the overdrive, which offers a final gear ratio of 10.97 in first gear.

 

Over the weekend, I will manipulate the shift linkages to determine all the gears, so I know exactly what I've got. Changing the gear set isn't cheap, and it might e better to sell a Brewer built transmission, and start over with a different transmission if the gears won't work for a flattie. Dan Brewer will swap gears with me but it would still be hundreds of dollars if I want a gear set of comparable condition. I don't need to do burnouts, i just don't want to burn out clutches trying to get started.

 

What are the actual ratios of the Pilothouse 3 speed transmission, anyway?

[kencombs]

21 hours ago, Los_Control said:

$10 on Amazon

A countersink is the correct approach to the problem.   But be sure to buy the correct angle.   Most hardware store/woodworking ones will be 90deg.   The most common used in automotive work will be a 82deg.  

[John-T-53]

The 1953 shop manual lists the following gear ratios for the 3-speed transmission which came in the B4B, C, D, & DU. I'd guess that the transmission in the B1s would be the same or very close. 

 

1st 3.3

2nd 1.78

3rd 1.0

Rev 4.3

 

When combined with the stock 4.10 rear end, you can see where we end up. 

 

Does the 833 have any tags or markings where you could look up what it is exactly?

 

 

[Tony_Urwin]

Not really.  There is a manufacturing date which gives an indication of the available ratios for that year. Different ratios were available for the 18 spline or 23 spline input shaft. The multiple possible tailhousings on the A833 are another indicator of the possible gear ratios. To make it even more confusing, the gear sets could have been swapped at some time in the past.

 

The most likely gear sets for my 1974 cast iron model would have had either a 2.47 first gear (Challenger or Barracuda V8) or 3.09 first gear (slant 6 or 273, 318 V8). My transmission had a small block bell housing, so it could have been either.  It also had the long tailhousing with two shifter mounts which was used in B-body and E-body cars. Mine had the Hurst shifter in the rear location. Pretty confusing.

 

 

Edited November 5 by Tony_Urwin

[Tony_Urwin]

I bolted shift tabs onto the gear selector shafts and wrapped masking tape on the input shaft so I could do proper calculations of the gear ratios. My rough measurements give me 2.41/1.80/1.38/1.0, so I definitely have a close ratio A833. I have seen some indications online that first gears can be swapped in some versions of the A833. I will talk to Dan Brewer next week. If I can't get a lower first gear I will sell this A833 and look for another. Shame, because this one is in such beautiful shape. Shifts like butter, zero slop when I turn the shafts.

Edited November 2 by Tony_Urwin

[John-T-53]

Even if you still had the 4.10 rear it would be too high in first....

[The Oil Soup]

I have a T5 in my B4B 230ci with a Cherokee rear end (3.55), I also am running 17” rear wheels 31”h and with a mustang gear set  1st 3.35, 2nd 1.94, I can take off in 2nd, not ideal but 2.47 would be better. The stock 3 speed was 1st 3.3, 2nd 1.78, 3rd 1.1.  

I followed John-T-53 T5 build thread and it was a great help. YRMV

[Tony_Urwin]

Soup, I am surprised that you can even take off in second without stalling. That 1.94 second gear and a 3.55 rear axle give you a final gear ratio of 6.89!

 

Sure, the 2.47:1 first gear on the A833 is better, but this close-ratio A833 was originally used behind big V8s. Are you suggesting that it might actually work behind my 230? I know that guys with the 4-speed will often start in 2nd.  What's the 2nd gear ratio on the 4-speed?

[Veemoney]

I put a 3.54 gear in my truck that has the stock 4-speed. I take off in 2nd now all the time and start in 3rd on occasion. Before with a 4.10 rear gear I started off in 3rd all the time. Tires are 225x70x16.

For my set-up I feel a 3.23 would be ideal but want to keep my stock housing so I am content for now. Drove it for years with the 4.10 gear though.

[9 foot box]

   I was reading LostVikings thread before he deleted his posts. When he got the OD transmission in, it stopped short of the adapter plate. He did have to sleeve the release bearing to fit the front bearing retainer. It will be good to talk to Dan Brewer again about a possible 2.66 first gear change and what other parts would be needed in that change. The cars that used that transmission were most likely geared 3.23. You won’t be hauling any loads or stopping on uphill grades. I’d run what you got and determine if you need any gear change after driving it for awhile.  Rick D.

[nkeiser]

I have an A833 out of an 80's pickup, so it has the 3.09 first gear. My rearend is a Ford 9 inch with 3.73 gears. I have no drivability issues. Starts in first great. Cruises down the highway at 65 in third. Overdrive maintains speed well, but gutless on hills or accelerating. Tires are 275x60x15.

 

Magically, my stock speedometer is only 5 mph off after that odd combination. I was impressed that a generic replacement cable from O'Reilly's fit between the transmission and speedometer that were 30 years apart and was that close.