904: should I switch to 727?

[QuickDart360]

Keep the 904.
Even better if you can find a 999 or 998 from the late 70's to early 90's (Basically a beefed up 904 the 1980's version had wide-ratio 1st & 2nd gears, 2.74/1.54/1.0 vs. the normal 2.45/1.45/.1.0 1st, 2nd and 3rd gears)
--A lot of the F, M & J platform cars in the late 70's & 80's had these as well as V6 magnum Dakotas and some vans etc. For Example mine came out of a *1988 Dodge Diplomat Police Cruiser. (Plymouth Gran Fury was the "corporate twin")
I've been daily driving a 10.2 compression 360 with it for nearly 60,000 miles. No issues. Done many 500+ and 1000+ mile trips, it has never let me down.
Mine was rebuilt using a deluxe HP rebuild kit Kevlar bands, kolene steels and red eagle clutches.
I also put in a stage 2 Cheetah valve body kit from Turbo Action.
The ole' transmission tech who helped me rebuild mine (he's been doing it for over 30 years) assures me that mine can easily handle the 450+ hp 408 stroker I'm building at the moment.
---> He did tell me to get rid of the 8 1/4 rear axle that have. (I also have an 8 3/4 that I'm assembling)
Don't get me wrong the 727 is a good transmission it's just heavy and soaks a bit more horsepower than the 904. (I read somewhere that it's like 45 hp vs. 24 hp)
There's a guy locally here in UT that I talked to years ago at a car show, he had a 490HP 3G Scat Pak Hemi bolted to a modified 904 and has no issues.
-- (yes the new 3G hemi's will bolt up to a SBM pattern transmission, they just don't utilize the 12 o'clock bolt and need a spacer due to crank offset)
This is not the exact site I used in the past but something similar: A904 HP Rebuild Kit A998 A999 Master Banner Overhaul Automatic Transmission Dodge Chrysler Jeep

*Those Diplomats & Gran Fury's were sure ugly but in a kind of a lovable way (like a warthog), but they do make great unassuming "Sleepers" (they do have a following with respect to the dippy.org goons)
Nothing like watching a some young guys face when his new Mustang GT gets left in the dust by some ugly 1980's Minecraft looking monstrosity of a car.

FYI 8 1/4 rear ends are strong with sure grip units. No need to go to 8 3/4.

 

[CudaFactHackJob]

I wouldn't slam the th200. I built one with stock parts and a shift kit back in about 90 and ran it behind a 400 sbc in a 78 Futura....no problems..

 

[Dale Davies]

I would suggest a shift kit or valve body upgrade for ALL transmissions. I put manual valve bodies in all my trans, 904 and 727. The TA RMVB in my 904 would swap right into a 727 if I were to choose to. If the 904 in my Duster fails, I will rebuild it or the other 904 in my garage. How would I be "money ahead" by purchasing a SB 727 along with the proper slip yoke rather than just slightly beefing up the 904 I have ?

I wouldn't slam the th200. I built one with stock parts and a shift kit back in about 90 and ran it behind a 400 sbc in a 78 Futura....no problems..

Built they are OK with the shift kit. Off the factory floor they were a bit limp wristed. Worked at a Chev dealer and did warranty repairs on many of those. Of course under warranty you only tear it down as far as necessary to repair the failure. The ther of course is under warranty there was no shift kits installed.

 

[crackedback]

If you are gonna spend money on something like a valve body scrap the 904 and go 727 instead. You'll be money ahead

same valve body

904 don't detonate is my primary reason to not run a 727 behind a SB. You can spank a 727 sprag spinning the tires and them suddenly hooking in first gear. Only way I'll ever run a 727 is with a billet drum in it and that isn't even a guarantee to not explode (seen two of those let loose).

 

[Dale Davies]

Yup, same valve bodies. Reprogrammed with some drilled restrictors and different springs. Takes the slip and slide out of the shift to improve durability without giving whiplash.

 

[Just Send It]

My Cope Racing 904 RMVB is rated up to 850hp with a transbrake. I've owned 3 of them and they've never given me an issue. When fully built, they cost about the same as a 727. My car weighs just under 3000lbs.

Cope told me the 2 things that kill 904s are heat and shifting too low in the RPM range. 904s like to spin. Not too difficult to manage with a MVB but if your kickdown linkage isn't set right, you can hurt them. Just my experience

Both the 904 and 727 have their advantages and disadvantages. Just depends on the goals for your car.

 

[Cuprum-74]

FYI 8 1/4 rear ends are strong with sure grip units. No need to go to 8 3/4.

Not with a 408 Stroker pushing over 450 HP.
I have a Mike McCoy here in Lehi, UT whose been building rearends and transmissions for over 30 years tell me the same thing, he told me about 350HP & below is what he calls "safe" for a stock sure-grip 8 1/4.
Plus, I already have all the parts minus the ring & pinion to assemble an 8 3/4.