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Discussion Starter #1
I am looking for some ideas and advice on how to put together an effective solution for a TH400 to be used in autocross/roadracing.

The car is a 1987 Buick Turbo T with a stock engine and a laundry list of bolt-ons which has allowed the car to run 12.1 @ 113mph using a modified 200-4R with non-lock-up 3000rpm stall converter and 3.08 gears. The car currently runs a built TH400 with a transbrake, reverse shift pattern manual valvebody and small diameter 3300+ rpm stall converter (which slips ~20% at the dragstrip). For street driving and semi-competitive autocrossing this iteration of a TH400 has proven to be pretty damn ineffective compared to the old 200-4R with a tight 12” 2000 stall converter (installed prior to the 3000rpm unit mentioned above) in the cones.

I’d like to keep the functionality of the RMVB, but would like to add engine braking back in (this is a bit of a heavy pig and needs all the help it can get slowing down); TCI offers this with one of their RMVBs (P/N 221201). When autocrossing I typically leave in 1st gear and grab 2nd once moving and leave it there for the entire run. The car makes very little boost on most autocross courses so I spend a lot of time running off the wheezing V6 in NA mode; that said I believe small diameter converter, with anti-ballooning plates, in the 2200 to 2400 range is going to be preferred due to maximizing low-end torque. I am not concerned about the low stall speed impacting the car at the drag strip as there is a yet-to-be tested nitrous kit in the car for off the line spooling.

If the TCI RVMB seems like a good idea, what else should I be looking to add to a stock TH400 (I am looking into a new core) in order to build it up to handle a car that should do 400-500hp and gobs of turbocharged torque?

Specifically: general modifications, hard parts, clutch material type, bushings and bearings, seals etc? And what vendors should I be looking to for this stuff?
 

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I think the best way to do an autocross TH400 would be to make a spragless version. The intermediate band will be short lived in any real loaded decel situation.

That doesn't really exist so I would call Hughes for the RMVB with engine braking.
 

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Discussion Starter #3
I think the best way to do an autocross TH400 would be to make a spragless version. The intermediate band will be short lived in any real loaded decel situation.

That doesn't really exist so I would call Hughes for the RMVB with engine braking.
The good news with auto-x is the car never really gets going that fast for very long, and in most cases the brakes do most of the braking. However, there is a distinct advantage to having assisted braking from the engine; especially in a nose heavy car where more balanced braking is preferred.

Is there a particular advantage to the Hughes RVMB over the TCI unit? From a price point perspective they are in the same ballpark, but I am wondering if there is a quality/functionality benefit to the Hughes product line?
 

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Discussion Starter #5
The Hughes valve body works...
Simple enough. Thanks for the input.

Can anyone suggest what I need with respect to hard and soft parts (any recommended kits)? Is modifying the internals to fit extra clutches a worthwhile endeavour?
 

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Discussion Starter #7
Why not put a TH350 in it. Most all manual valve body's for the TH350 retain 2nd gear engine braking. Plus it will use less HP than the th400.
If I do an alternate transmission that uses less power I am going to drop another 200-4R back in the car. But, given that being robbed of a few ponies isn't a concern for me - I doubt that'll sway me. Plus I've already got a fair bit invested in having had already modified the car for the TH400 (everything from electronics to the driveshaft), so switching transmission types again means a fair bit more work and cost.

Okay this raises a question: Does the Hughes TH400 RMVB suggested above only provide engine braking in 1st gear? I got the impression that engine braking was maintained throughout all 3 gears.

If there are other ideas out there on how to build a TH400 for my application I am all ears.
 

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No BUILD advice from me but here's a significant data point:

In my area of Eastern PA, the SCAA had a class where the 2 top cars were a 1970 SBC Z28 with the stick 4-speed and a 75 455 T/A with the TH400. Those 2 cars traded 1st place numerous times in their common class, showing the TH400 is competitive when the CAR is driven properly.

Quite familiar with the engine.
 

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Discussion Starter #9
It seems that I have asked an extremely unconventional question, which is limiting peoples' ability to respond? Or I am looking for a complex answer to a simple question and no one wants to answer the samething over and over again...

If the answer is: "just build a basic TH400 and you'll be fine..." Please say so and I'll get on with it.
 
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It seems that I have asked an extremely unconventional question, which is limiting peoples' ability to respond? Or I am looking for a complex answer to a simple question and no one wants to answer the samething over and over again...

If the answer is: "just build a basic TH400 and you'll be fine..." Please say so and I'll get on with it.
A good stock rebuild on a th400 will hold 400-500hp all day. Use your choice of VB I would say a stage 2 transgo kit in a stock VB would work fine. If you want a full manual the get one that has engine breaking. Oh, and put the biggest tranny cooler you can fit, a aluminum pan would be a good idea too. :D There I said it secrets out. Sorry guys. :rolleyes:
 

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It seems that I have asked an extremely unconventional question, which is limiting peoples' ability to respond? Or I am looking for a complex answer to a simple question and no one wants to answer the samething over and over again...

If the answer is: "just build a basic TH400 and you'll be fine..." Please say so and I'll get on with it.
Use a late 4L80E intermediate band and servo assembly. Crank the pressure up to 200 lbs. Use the Hughes VB it has engine braking in low and 2nd.
I don't typically use them but this is a good application for waffled clutches in the intermediate and directs.
Stock shafts will probably be fine.
If you are seeing higher rpms and running mostly in 2nd, leave the clutch pack clearance on the directs on the looser side.

A TH350 would be a disaster in this application AND probably consume as much or more HP as the TH400.
 

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A rebuild with updated parts will serve you well. IMO you would be better served with a smaller tranny. you want the smallest transmission that can be reliable. that 400 is probably killing that cars performance.
 

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Why not put a TH350 in it. Most all manual valve body's for the TH350 retain 2nd gear engine braking. Plus it will use less HP than the th400.
I think the 350 or 2004r would be the best choices.Very low drag.The 400 is the choice for drag racing but for road course and autocross there is really no sense in dragging around all of that extra weight.The band is only used as a wedge for driveshaft input.This is evident by the side of the case the engineers put the servo piston and the diameter of the piston.You could even run 3 clutches in low gear in either 2 and reduce parasitc drag when the rear carrier is driven in all forward gears except 1st.250 and 350 c liteweight parts and youve got a big reduction in power loss.A lot of circle track guys run the th350 with excellent experiences.
 

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No BUILD advice from me but here's a significant data point:

In my area of Eastern PA, the SCCA had a class where the 2 top cars were a 1970 SBC Z28 with the stick 4-speed and a 75 455 T/A with the TH400. Those 2 cars traded 1st place numerous times in their common class, showing the TH400 is competitive when the CAR is driven properly.

Quite familiar with the engine.
Auto-crossed TH400 was reliable. The Case took the hi-gs. The guts took the 455 accels and decels. Bars & tires, then driver. Or is it driver & tires, then bars? Driver, bars, then tired?
 

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Discussion Starter #15
The good news is that the car already has a deep pan and large Derale oil cooler with a fan so that will transfer over easy enough.

The car/trans will not see significantly high RPMs as this POS Buick engine chokes out at 4800-5000rpm... and takes forever to get there thanks to a lousy head design, wimpy cam and 3.08s in the diff.

With respect to the power sapping issues using a TH400 vs. the 200-4R: this car has ET'd the exact same off the footbrake with no change in MPH despite the transmission used. Remember this little 3.8L only makes torque and likes to be loaded up because of the turbo. I think it is better suited for towin', than racin'!?!

I am pretty sure it is driver, tires and then a trip to the bar...

Gents thank you for all the feedback. You've given me a lot to consider and I hope to pass some business on where ever possible.
 
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