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View Full Version : Is this guy correct, or all wrong???


BillyGman
02-19-2006, 02:48 PM
This is what someone is telling me on another board about running a full manual valvebodied automatic transmission on the street (a TH400 trans). Is he right or wrong??......


"Most manual valve bodies eliminate engine braking because they eliminate the intermediate band and some of the circuits that operate the low gear clutches or band.

On a race car that only operates under a powered upshift this isn't really an issue. However you can stress parts on the street when you are decelerating and the trans is over-running, or "free-wheeling" and you accelerate hard.

Most trans-brakes for a Th400 are of the full manual reverse pattern type VB and eliminate the engine braking feature. That is why it was brought up."
chasrein01
02-19-2006, 03:06 PM
I had a reverse manual on my '65 Mustang C-4 trans. It eliminated the engine braking on low only, which makes sense - your rpms would really shoot up if you were to shift from 2nd to 1st (let alone a miss from 3rd to 1st, just because of the gear ratios inside the tranny) and tear up your engine even if you weren't giving it gas to keep the rpms up. Your valves could "float" and make contact with pistons, they could even break off the stems and land on the pistons..... you get the picture.
BillyGman
02-19-2006, 03:24 PM
So then what this guy is saying is garbage??? Thanks for sharing. I was hoping to hear from somebody like you who actually has driven a car on the street with a full manual VB.
chasrein01
02-19-2006, 04:35 PM
I don't know about the exact internals about the tranny, but that was the reason explained and needed for my version. I was running 11.5:1 compression and .60 over pistons, 2.02 / 1.60 valves, erson roller rockers, mechanical cam, and 750 cfm carb. Only the water pump, fan, and alternater to pull hp from the engine, so I thought the extra safety of the "non-engine braking" in 1st really made sense to me. I frequently ramped up the rpms over the 6,000 rpm tach in while in 2nd (somewhere around 1.36 gear in the tranny / the 1st gear is somewhere around 2....) so you could imagine the rpm jump if I messed up!
TheDealer
02-19-2006, 08:24 PM
My 67 Comet has a 460 engine with a th350 manual valve body with a trans brake. Street driven car.
chasrein01
02-20-2006, 06:50 AM
Probably moves out promptly!!
BillyGman
02-20-2006, 12:11 PM
My 67 Comet has a 460 engine with a th350 manual valve body with a trans brake. Street driven car. Thanks Ray.