I have a 1982 AMC Spirit which came with a 904 transmission. I understand that this is a light duty transmission but would like to know what upgrades I can try to make it live behind 350 ft/tq. I read that I can swap in internals from a 998? The car is also a challenge vehicle and I’m running out of build time. Is it’s worth installing a shift kit or just leave it stock and hope for the best for now?
Also did any versions of this transmission come with a kick down cable? I need to rig up something to replace the rod assembly that will no longer fit with the new engine.
The 904 is a pretty tough transmission. It's actually preferred by a lot of drag racers due to the lighter assembly. Mine lives quite happily behind a 375 torque to the wheel 340 with just a factory rebuild and a tranny cooler.
Lokar makes a kit for a cable kickdown:
http://www.jegs.com/i/Lokar/625/KD-2904HT/10002/-1?CAWELAID=1710578441&CAGPSPN=pla&catargetid=230006180000848257&cadevice=c&gclid=CKaTiJPA9cACFUkJvAodQokAJA
There was not one factory at least from the mopar side.
They have been abused in Ultra 4, W.E.Rock, and similar Rock Bouncing, Crawling, Racing behind any number of engines. The Supercharged GM 3800 Series II was popular for a while, and the 904 was the go to transmission for a RWD application, since it's short and conveniently, at least in Jeeps, shares the GM Metric bolt pattern.
I known of a guy that was nationally competitive with that very combo and a bone stock 904, it took A LOT of neutral drops with giant sticky tires and low gearing before he finally killed it.
Do you know if your 904 is the lock-up version or not? If it's a lock-up you'll want to shim the lock-up valve so it doesn't engage the converter clutch.
The 904 is a pretty rough little trans. For a Challenge car, unless it's currently dead, I'd run it as-is. If you are dropping the pan to change the fluid & filter go ahead and do the shift kit. The TransGo TF kits are the ones to use. Do you want the trans to shift for itself or are you going to manually shift it? The TF2 kit will probably do what you want. If it's a non-lock-up trans the full manual TF3 kit will work.
The kick-down linkage is necessary unless converting it to a full manual valve body. It's really a throttle valve. The rule of thumb is the lever on the trans needs to be bottomed out at full throttle. The Lokar piece is nice, but for a Challenge vehicle snagging the cable setup from a '90's Ram/Ram Van/Dakota and adapting it to carb use is a more budget friendly solution. I think the late model setup is a pull configuration vs a push setup like the earlier Mopar rod linkage.
For something beyond Challenge use I'd do some other upgrades, but no need to blow the budget on them right now.
Rob_Mopar wrote: I think the late model setup is a pull configuration vs a push setup like the earlier Mopar rod linkage.
So's the Lokar setup. The Lokar one bolts to a tab on the back of the transmission; not sure about the OEM version.
The 998 and 999 are variants with a wider gear ratio spread and extra clutch plates. I have thought about using some of their internals on the Dart at some point, but swapping the parts in is probably overkill for a Challenge car.
I think its the lock up version but i'll need to double check. I've already dropped the pan to drain the fliud before pulling it. Shift kit wouldn't be that bad to do right now but if you think the trans would be fine stock then thats my cheapest option. Currently it has 104k miles on it.
Well at the challenge I learned that the transmission slips. We dropped the pan again in the hotel parking lot after a tuning run and there was already a bunch of junk in the bottom. We couldn’t make any decent drag passes since it just slipped as soon as boost built up. Over the winter I’d like to come up with a plan and start gathering parts for next year. Should I rebuild the stock trans or find another and hope for the best? I need something that will handle about 400 ft/tq.
You'd have to find an AMC patterned one to swap it wouldn't you? I don't know about your budget but you could at one point get Alto clutches and kevlar bands for the TF trans. That with a shift kit and a big cooler would be my course of action. Not sure you can beef it up anymore without blowing your challenge budget.
Yeah, I’d need to find one with an AMC pattern case. I started to price things out the other day, stock rebuild with a shift kit would cost about $115. Upgrading to Alto or Reybestos would be another $40-50. Might need a new oil pump too. Prices are just from a quick search. I have a few hundred left in the budget but this would eat up a good chunk of that.
Is the AMC I6 pattern same as the AMC v8? They used the TF 727 behind those, it would give you a better base to start with since they are use so often in drag racing.
Yes the AMC I6 and V8 share the same pattern. The 727 is 4" longer I think so I'd need to shorten the drive shaft. Also I'm not sure if the case is bigger. Another oprion is an AMC pattern TH400 but that would have the same issues as swapping in the 727. Still haven't ruled either out.
Swap in a AX-15 manual out of a XJ?
Just a datapoint here, but I can buy noname rebuild kits for about $60...
44Dwarf
UltraDork
11/10/14 7:40 p.m.
Did you try adjusting the bands? You may have been able to lock it in high gear.
kits can be cheap but you'll want the good raybesto's red bands. I do know a guy up here in Winchendon who does trany's on the side in the winter as he drives a concrete truck he gets laid off most winters he drag races with a 904. shoot me an e-mail I'll get you his number
Kenny_McCormic wrote:
Swap in a AX-15 manual out of a XJ?
there is no way an ax15 will last with 400 ftlbs of torque
The first CarCraft magazine I ever bought dealt with 904s. "904 vs. the World." You can get them built with 727 guts. Something that strong that weighs as much as a Powerglide? I have no idea why more drag racers don't use them.
Along the same train of thought as AX-15, I was thinking AW4 out of a 2wd Cherokee. The TCM is stupid simple and can be adapted to button or paddle shifting with a little Google-Fu and a soldering iron. AW4s also have a lot of interchangable parts with the A340E from the Supra. Surely something semi-awesome can be made from this.
MrChaos wrote:
Kenny_McCormic wrote:
Swap in a AX-15 manual out of a XJ?
there is no way an ax15 will last with 400 ftlbs of torque
I was under the impression there are plenty of V8 swap jeeps running around just fine with the stock AX-15? Novak calls it "well matched" to the LSx. The Supra people don't seem to complain about them in R154 trim.
Rebuilt it. 904s make great drag transmissions.
The only fatal flaw with Torqueflites, literally, is manually shifting them into second at high rpm's. The band applies to the direct drum to stop something turning 2x engine rpm.... Eventually the drum fatigues and explodes taking everything from your knees down off if you are unlucky. That's why they make an aluminum direct drum and it costs $600.
In reply to Kenny_McCormic:
that is because they are cheap and plentiful. the ax15 is marginal at best along with the NV3550 being a slight upgrade in strength. The NV4550 is the better option for a manual.
In reply to MrChaos:
So how many have you blown up?
I’d love to swap in a manual but I think that might be more expensive then fixing the 904. I’d need to source a pedal assembly, clutch master and lines, flywheel, decent clutch, and the transmission its self. The AX-15 has a low first gear and would not be too ideal. If I went with a manual I’d try to find a R154 from the Toyota Supra Turbo MKIII because it can be adapted since its closely related to the AX-15 but with better gearing. The other option is finding a WC T5 and a AMC bellhousing. I’m not ruling any of these out yet incase I find a great deal on parts or whole cars.
I know people have swapped in 2WD AW4’s but I’m not sure what they used for a driveshafts or if there are any other fitment issues. We are using the stock one in the XJ-R with 240K and its been holding up so far. Shifts are slow but at least we’ve wired it for full manual control using the stock shifter for gears 1-3. This could be a good option since Jeep guys normally scrap the 2wd trans.
Another thought on the 904, some of the shift kits allow full manual control over the transmission. Would I need the throttle valve cable if I only have manual control? Reason I ask is I have $35 into the cable kit since I was short and couldn’t build a junk yard setup. Shift kit would save me $35 if I can ditch the cable.
In reply to PseudoSport:
I mean you could do a cabin mounted cable setup to control the harshness of the shifts with a properly mounted line psi gauge for the ultimate in manual control.... 
