A904: 1-2 shift happens early despite governor weight- any way to adjust this?

I'll be honest. I love manual gear boxes and I'm fairly clueless about slush pump transmissions. I have great faith in the honored Chrysler Torqueflight...so if I can't row my own gears, this is the transmission I would pick. Anyway, If this is an ignorant question, I beg your kindness in advance.

When getting my Dart back on the road a few years back with the Magnum swap, my budget demanded that the manual transmission transplant be put off for some future project so I did the best I could with the stock A904.

I had a local shop, Best Transmission in Springfield, MA do the rebuild/upgrade work. They have been around for more than half a century and plenty of old hotrodding knowledge is still on staff...good guys up there. I told them what my goals were (strong enough for a healthy small block, firmer shifts, higher rpm) and they helped me pick out some components. They were impressed how despite 140k miles behind a 318, the transmission was in nearly perfect condition with plenty of life left, had I not been looking to upgrade. No surprises there for a lot of you guys, I'd guess.

Anyway, I've been slowly chipping away at the tuning for the past few years and the car is running better all the time. What I'm finding is that the 1-2 shift is happening at about 4,400 RPM while the 2-3 shift is happening around 5,300 (about where I would want it, I suppose). Is there some means of adjusting one shift point but not the other? The transmission shifts firmly and kicks down predictably...I think I'm just giving up a huge amount of performance with that early 1-2 shift.

This is the setup:

Magnum 300 5.9 crate engine with the stock mild cam.
A904 with stock ratios for 1973/318 car
Upgraded clutches/bands, deep pan
Transgo TF2 shift kit
"5800 RPM" governor weight (subject to many variables, I know)
TCI Streetfighter/2600 RPM stall
4.10 final drive

Any suggestions are welcome.

You have to change the 1-2 shift spring in the valve body. In addition to the governor weight, which it sounds like you have already changed, you sometimes have to put in a heavier 1-2 shift spring to make both shift points match. A&A transmission sells them, they are cheap. You will have to pull the valve body to change it.

As it is, your wide open throttle shift points should be higher, nearer 5800 as that is the weight you put in. Make absolutely sure that your tv (throttle valve, kickdown) linkage is properly adjusted, all the way back at WOT and all the way forward at idle. By this i mean the actual lever on the trans.

What kickdown linkage do you have Factory or Lokar ?
Could be as simple as a kickdown adjustment.

The kickdown adjustment will affect both shift points the same. If there is a split between the 1-2 and 2-3 that you want to correct you need to use the A&A 1-2 springs to make the shift points match.

Try first to lengthen the trans shift linkage, It seem to affect the 1/2 or than the 2/3 shifts in my experience. Make sure the linkage is set up like original.

d55dave said:

You have to change the 1-2 shift spring in the valve body. In addition to the governor weight, which it sounds like you have already changed, you sometimes have to put in a heavier 1-2 shift spring to make both shift points match. A&A transmission sells them, they are cheap. You will have to pull the valve body to change it.

As it is, your wide open throttle shift points should be higher, nearer 5800 as that is the weight you put in. Make absolutely sure that your tv (throttle valve, kickdown) linkage is properly adjusted, all the way back at WOT and all the way forward at idle. By this i mean the actual lever on the trans.

Click to expand...

Damn. If this requires changing the spring, I'll have to write it off as a tax on ignorance and leave it be. I don't foresee pulling the transmission again any time soon.

I'll double check the linkage...I did my best to adjust it as you described but perhaps this situation is an indication that I didn't get it quite right...?

Johnny Dart said:

What kickdown linkage do you have Factory or Lokar ?
Could be as simple as a kickdown adjustment.

Click to expand...

Stock kickdown linkage with a lengthened rod...as above, you could be right. I just hope that I haven't damaged anything if it has been wrong. After 3-5k miles since the rebuild, the fluid is still bright red, no burnt smell...for whatever that's worth.

d55dave said:

The kickdown adjustment will affect both shift points the same. If there is a split between the 1-2 and 2-3 that you want to correct you need to use the A&A 1-2 springs to make the shift points match.

Click to expand...

Yeah...that's bad news. I'm not sure why this never came up in my pre-rebuild discussion with the shop.

66jim said:

Try first to lengthen the trans shift linkage, It seem to affect the 1/2 or than the 2/3 shifts in my experience. Make sure the linkage is set up like original.

Click to expand...

Interesting...Which component in the shift linkage specifically did you lengthen?

The rod from the carb should have an adjustment, if not
try to locate one or fabricate out of treaded rod with a turnbuckle for adjustment. From my experience the lenght is a
pretty fine adjustment, too long and the throttle may not be 100% back too short give early shifts. This setup is best taken complete with springs from an unmolested
donor car.

The factory kickdown linkage was sloppy at best when new let alone now 45 to 55 yrs. later.
Since you do not want to go back into trans. Recommend a lokar kickdown cable & throttle cable combination. Relatively inexpensive and easy to install and adjust. Will insure you have kickdown all the way back at WOT and all the way forward at idle without slop.
Lokar throttle cable will help guarantee you are consistently absolutely at WOT to maximize kickdown performance

Lokar kickdown products are for people who don't have the proper factory parts, or have no clue how to properly adjust their factory linkage. Ma Mopar did just fine when she designed the linkage for these cars.

There are a couple places to adjust the factory kickdown. One adjustment can be made at the rod that attaches to the carb. If there is no adjustment there, then there should be an adjustment on the rod running along the firewall.

I would recommend finding a factory service manual, to properly adjust the kickdown. There are also a couple good videos on YouTube.

Disagree if you want maximum performance. If you want stock look and a driver keep factory stuff. It is Rube Goldberg at best with multiple adjustable knuckles and pins allowing for serious twist, slack and inconsistency. Just my personal opinion and experience though with many yrs. & cars of using both.

The trans doesn't have to come out to change the 1-2 shift spring, just drop the pan and valve body. It can be done in 1-2 hours.

I agree, the factory linkage is far superior to the lokar bicycle cable. If you must use a cable either build your own using junkyard parts from a magnum engined truck or van, or buy the bouchillon cable, which uses the same factory parts. It is a much better cable and brackets than the lokar.

Lokar = Band aid.
Personal opinion.

Have had great success with lokar setups on my early a’s personally. What is your issue.
Have you used and had problems? Just curious.