Hey guys. I thought I heard that someone was running a “low first gear 904”. Can someone explain what that is? Was that a specific factory model type or a modified first gear?
Low First Gear 904?
- Thread starter 340inabbody
- Start date
-
Vaanth
Well-Known Member
The wide ratio version of the A-904 was introduced in all Chrysler domestic rear wheel drive cars for the 1981 model year, both A-904 and A-998 variants. It was also introduced into the trucks using the A-904T and A-998. The new gear ratio set was released to work with the higher ratio (lower numerically) rear axles for better fuel economy in eight cylinder applications and improved performance in six cylinder applications.
The new wide ratio set changed the first and second gear ratio as shown in the following table:
| Gear | 1981 WIde-Ratio Gear Ratios | Previous Standard Gear Ratios |
| 1st | 2.74:1 | 2.45:1 |
| 2nd | 1.54:1 | 1.45:1 |
| 3rd | 1.00:1 | 1.00:1 |
| Reverse | 2.21:1 | 2.21:1 |
The change included a new front planetary and ring gear set, sun gear with sun shell, with matching bushings and thrust washers.
Last edited:
Thanks! So thats a completely different gear set. Ate TCI’s and other aftermarket trans run their own gear ratios or do they use factory ratios?
64mopar
Well-Known Member
I pick up a built up 904 with the low first gear for my Barracuda.
Vaanth
Well-Known Member
I haven't used any aftermarket stuff, but from what I've seen, some make their own, and some refurbish or reinforce factory parts. What I have seen listed is just the factory ratios. It can be added to earlier transmissions.
Was this an 81 or later core that was rebuilt?
64mopar
Well-Known Member
It was built by Hughs.
Locomotion
Well-Known Member
I believe a lot of the OEM low gear transmissions also had lock-up converters which don't interchange with regular converters. But they can be swapped into regular 904s if you know what parts to swap (including valve body?). Not sure what aftermarket low gears were made for a 904 but I've seen 2.77 and something like 2.30...something for 727s. Very expensive.
I used OEM 2.74 gearsets in my Dart Sport 904s. More gear usually helps heavier vehicles and smaller less torquey engines in drag racing.
I used OEM 2.74 gearsets in my Dart Sport 904s. More gear usually helps heavier vehicles and smaller less torquey engines in drag racing.
That’s kind of why I’m asking. My 340 is in a Bbody 1970 satellite which is 2 to 300 pounds more than an Abody.
What irony....
I asked a similar question just a few minutes ago on this forum. I didn't know that THIS thread was started a couple hours before me.
I have a 904 in my Dart, it was in my '70 Charger when I got the car in 2000. I wondered if it were a low gear version but wondered if ALL low gear versions came with lockup converters because mine is not one. I'd just look up the numbers but my transmission has none stamped where they are usually found.
I asked a similar question just a few minutes ago on this forum. I didn't know that THIS thread was started a couple hours before me.
I have a 904 in my Dart, it was in my '70 Charger when I got the car in 2000. I wondered if it were a low gear version but wondered if ALL low gear versions came with lockup converters because mine is not one. I'd just look up the numbers but my transmission has none stamped where they are usually found.
Locomotion
Well-Known Member
Lock-up started in the late '70's. I don't know if it's possible to I.D. lock-up & low gear transmissions externally aside from the pic I posted. No trans pan rail numbers may represent a warranty trans. Hopefully @Vaanth can offer more details from his wealth of information.
Vaanth
Well-Known Member
The lockup converter first appeared in the 1978 model cars as follows:
- 225 with A-904, federal applications
- 318 with A-904, federal and California applications
- 360 with A-999, federal and California applications
- 400 with A-727, federal and California applications
- 440 with A-727, California applications
- 225 with A-904T, federal and California applications
- 318 with A-998, federal and California applications
As noted, and shown in post #9, the input shaft differs on the transmissions between the non-lockup and the lockup. For the A-904, including A998 and A999 versions, the non-lockup input shaft has 27 splines and the lockup has 26 splines plus a smooth machined area without splines at the nose of the shaft. For the A-727, the non-lockup input shaft has 24 splines and the lockup has 23 splines plus a smooth machined area without splines at the nose of the shaft.
Transmissions with a lockup converter have a smooth turned down surface at the end of the shaft and a hole in the center of the shaft for the oil feed.
The following image also shows a comparison of the lock-up and non-lockup input shafts:
Although it may be gone, the original lockup converters were identified with a decal on the face of the converter which could be seen without transmission removal behind the lower cover. All lockup converters were 10-3/4" diameter, so a colored decal was placed on the front face of the converter to distinguish the use and whether low stall or high stall as follows:
- Blue on the 225
- White on the 318
- Red on the 360 and 400 (plus 440 in California)
NOTE: The lockup torque converter also has no drain plug, due the clutch friction area blocking the location. However, lack of a drain plug is not conclusive, because Chrysler removed the drain plug from converters in 1977, one year prior to the lockup introduction.
Externally, there is no ready way to identify the hydraulic lockup converter, other than the converter decal, if present, except by application part number. If the valve body is out, there are differences, but the tell-tale sign is the S-shaped aluminum tube on the upper part of the valve body.
The part number, date code, and build that day number, should be present on the left side pan rail. If missing, it might have been removed or missed. Errors in stampings occured, but it seems odd it would be missing entirely.
A warranty or service replacement transmission would normally still have this information stamped, but a 1969 or later transmission would not have the VIN stamped. 1968 and prior did not have the VIN on the transmission. Note that truck transmissions did not have the VIN stamped until the late 1970s.
Service replacement transmissions have a different number than the production number. These can usually be determined from information in the parts catalogs.
1969 and later housings have the VIN pad on the right side.
Beginning November 1, 1964, 1965 and later transmission housings had the base transmission designation cast into the lower left side toward the front on the converter housing area as shown in the following diagram:
The designations are generally as follows:
- 904G - six cylinder
- 904LA - 273, and later 318, 360
- 727A - 318 Poly, and later 340,360
- 727B - 361, 383, 413, and later 400, 440
A pre-1966 A-904 transmission will not have a splined output shaft for a slip yoke.
If a pre-1969 transmission, and if it is the original neutral safety switch, it will have a single threaded post terminal.
If 1969 and later, and if it is the original neutral safety switch, a 1969 - 1976 transmission has a slightly different three terminal neutral safety switch than 1977 and later.
Without the pan rail identifiers, and if things have not changed, then using some of these other external clues, plus main housing and extension housing casting numbers and date codes, the transmission model year might be narrowed down.
Last edited:
-
Similar threads
