Trying to determine what converter I’ll need

[chevytech87]

So I’m planning on tearing down my 87’ this weekend to swap my “new” 383 in. I’m currently running a bone stock 700r4 and a 305. I’m confident I’ll need a large, possibly very large, converter for the cam that’s in this thing. Disclaimer, I didn’t build this motor or select the parts. A coworker put it together for his OBS and decided to go LS instead. I’d love to hear everyone’s thoughts on 1: if the stock 700 will survive this swap 2: what size converter do you think it’ll need.
I’ve got a 3:73 Eaton posi that’s going in at the same time.

Here’s the build sheet:

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Thanks for taking a look!

 

[yevgenievich]

If plan driving it hard with a stock 700r4, will have to send the torque converter out to be opened and cleaned once transmission sends its internals through it. Maybe something on the used market for now and not beat up the transmission much until decide to take care of the transmission

 

[chevytech87]

If plan driving it hard with a stock 700r4, will have to send the torque converter out to be opened and cleaned once transmission sends its internals through it.

I figured that was pretty likely. I don’t drive super hard, but I like to make things as bulletproof as possible. How built does it really need to be I guess is my question. I can’t imagine that motor will make more than 450? On a good day? I just don’t want to spend more time and money than I need to on the trans, but I’m definitely not wanting to smoke a brand new expensive converter

 

[NickTransmissions]

So I’m planning on tearing down my 87’ this weekend to swap my “new” 383 in. I’m currently running a bone stock 700r4 and a 305. I’m confident I’ll need a large, possibly very large, converter for the cam that’s in this thing. Disclaimer, I didn’t build this motor or select the parts. A coworker put it together for his OBS and decided to go LS instead. I’d love to hear everyone’s thoughts on 1: if the stock 700 will survive this swap 2: what size converter do you think it’ll need.
I’ve got a 3:73 Eaton posi that’s going in at the same time.

Here’s the build sheet:

You must be registered for see images attach

Thanks for taking a look!

The stock trans won't last too long unless you drive it like an 80-year old going to the grocery store. You will also need a converter with a much higher stall than stock. Contact the manufacturer of your cam to obtain guidance on stall speed range for the grind you'll be using. Depending on power levels and pct time at the track (if any), you'll need to case and hydraulic upgrades, starting with:

- Corvette 2nd gear servo assembly (at minimum); should consider Sonnax super hold 2nd gear servo (and 4th gear servo if planning on doing high-speed street pulls in OD, etc)
- Governor mods depending on desired shift points and converter stall
- New detent (TV) cable
- .500 boost valve
- Ground-down land on the PR valve for line to lube
- Pump working surface reconditioning to bring your rotor/slide clearance into spec (.002-.0025 rotor and slide to deck surface clearance)
- Unbreakable pump ring kit (Transgo)
- Updated TV valve (Transgo SK700R4JR shift kit)
- Clutch feed/exhaust holes spacer plate drilled per requirements/vehicle overall set up/intended use
- Certain case and v/b check balls left out, depending on other mods
- MTV upshift valve spring removed
- Line Bias valve spring removed and replaced w/rod to block valve movement
- Modified/shimmed 1-2 accumulator housing w/piston (or Sonnax pinless)
- New rev input drum with wide kevlar lined or Alto red 2-4 band (20% wider than a stock BW high energy band)
- Blocked-off 3-4 accumulator
- Beefed up 3-4 clutch pack
- High energies throughout unit
- high rate return springs in the forward drum (Transgo's kit works fine)
- 4L60E late model bonded pistons and ret spring assembly
- Sonnax reinforcement sleeve kit for the forward drum (comes with it's own coast clutch apply piston).
- Lube mods to your front/rear sun gears to promote better lube to planetaries/ring gears
- Possibly 5 pinion GM OEM front and rear planets
- 07+ 4L70E induction hardened reaction shaft w/bearing
- Sonnax smart shell

Let me know if you need more info or have ?s.

 

[Matt69olds]

Call your converter company of choice. Have as much info on the vehicle and engine as possible, the more info you have, the better job they can do selecting the right pump/stator/turbine combination to match.

Don’t panic if they tell you a much higher stall speed than you think you need. Converter design has come a long way. A loose converter won’t feel mushy at part throttle. And if you keep the lockup functioning, once it’s locked you won’t notice the converter stall speed.

Install a good transmission cooler, and above all, make SURE the TV cable is right!! You will burn up a transmission driving around the block if the cable is wrong. Get the right tv cable brackets, ideally set up the cable with a line pressure gauge.

Too many people think as long as the cable is tight at WOT, all is good. Tight at full throttle is important, but it’s the other 95% of throttle position that will bite your ass.

 

[Snoots]

At this point, I'd put it on a pallet and send it to Nick.

 

[chevytech87]

At this point, I'd put it on a pallet and send it to Nick.

Not a terrible idea…

Install a good transmission cooler, and above all, make SURE the TV cable is right!! You will burn up a transmission driving around the block if the cable is wrong. Get the right tv cable brackets, ideally set up the cable with a line pressure gauge.

I do already have 2 additional coolers waiting in the pile of parts for the truck, however my transmission knowledge pretty much ends at heat=bad as I’m sure y’all can tell. The TV cable thing scares me a lot. I’ve seen others stress the importance and probably need to do some YouTube research on setting all of that business up.

Would it be foolish to buy a unit at this point as opposed to building my current one? Just from a cost standpoint?

 

[Camar068]

Another option to look at is upgrading to a 4l60E or 6l80e trans. You'll need to get a controller, the transmission, as well as adapters.

Make a list of prices for each option/benefit and figure out whats in your budget.

Or......convert to manual ...probably cheaper.

All to eliminate the trans cable worries if you want to.

 

[chevytech87]

Another option to look at is upgrading to a 4l60E or 6l80e trans.

If I had decided earlier to go LS instead of the 383 then that’d be the way I’d go for sure. However, for this build I’d really like to keep the 700. This is a driver, so I want to keep the OD otherwise I’d put a cheaper more reliable (from what I’ve been told) trans like a turbo 350 in it.

I probably could have saved a bundle swapping to newer tech, but hey, I’m here now. Oh well. That being said, I do appreciate the suggestions. I’ll see if I can make a cost comparison with what Nick so kindly provided and see where the numbers fall. I know a new complete unit with similar components will be north of 2K, probably closer to 3K? I’ll get some stuff together and post it up.

 

[bucket]

Converters are very expensive these days, compared to just a few years ago. I don't think I'd want to spend the $ on a newer high stall unit, just to smoke the trans in a few thousand miles and render the "new" converter as junk.

 

[chevytech87]

Converters are very expensive these days, compared to just a few years ago. I don't think I'd want to spend the $ on a newer high stall unit, just to smoke the trans in a few thousand miles and render the "new" converter as junk.

My thoughts exactly.

 

[chevytech87]

So after some looking, I’m wondering if this may be the right direction to go in for me. The thought is buy a new unit, build the old one on my own time without having to rush to get it back in the truck so I can still learn. Here’s what I’m thinking about:

Performance Rebuilt 700R4 Transmission, Level 3

Level 3 - Performance Rebuilt 700R4 Transmission, Call to order your 700 Raptor from Performance Automotive Transmission Center today! 318-742-7754!

transmissioncenter.net

Maybe overkill, but hopefully pretty solid? Open to thoughts…

 

[NickTransmissions]

So after some looking, I’m wondering if this may be the right direction to go in for me. The thought is buy a new unit, build the old one on my own time without having to rush to get it back in the truck so I can still learn. Here’s what I’m thinking about:

Performance Rebuilt 700R4 Transmission, Level 3

Level 3 - Performance Rebuilt 700R4 Transmission, Call to order your 700 Raptor from Performance Automotive Transmission Center today! 318-742-7754!

transmissioncenter.net

Maybe overkill, but hopefully pretty solid? Open to thoughts…

All those parts they're installing great but you can likely have a local builder build you the same or better transmission using your unit for a good deal less. Plus he'd be local to you so if it needs to go back to him under warranty, you dont have to worry about shipping.

Re that 700r4 in the link, I'd swap their sun gear reaction shell with a Sonnax smart shell as it's fully rollerized when paired with a 07+ induction hardend reaction shaft from a 4L70e. I also dont see Transgo unbreakable pump rings, late model 4L60E bonded steel/rubber forward drum pistons and ret spring, Sonnax fwd drum reinforcement sleeve kit, tubular steels in the low reverse and reverse input drum, wide Alto 2-4 band. I also sometimes rollerize the pump-rev input thrust surface using a th350 pump bearing and 200-4R direct clutch bushing in place of the factory bushing to locate the bearing (this mod has you omit the plastic thrust washer on the back of the pump). Doesnt mean they cant do those as well but likely means price goes up from there.

Just a few initial thoughts...

 

[festina_lente]

FWIW, I drive my turbo 400 backed motor all over the place at highway speeds and it's just fine.
The motor has to spin a little, but 70 mph is fine and probably about as fast as I should drive a 6-in lift 'Burban anyway.
I'm about to swap in a similar (slightly milder) 383. Other than a converter swap, I have no worries about it holding up. Indefinitely.

 

[NickTransmissions]

FWIW, I drive my turbo 400 backed motor all over the place at highway speeds and it's just fine.
The motor has to spin a little, but 70 mph is fine and probably about as fast as I should drive a 6-in lift 'Burban anyway.
I'm about to swap in a similar (slightly milder) 383. Other than a converter swap, I have no worries about it holding up. Indefinitely.

They're great transmissions. Up to 700 hp street/strip the only major hard part upgrade I typically do is a billet, rollerized fwd clutch hub (and sometimes a 97+ 4L80E direct drum for its 34-element intermediate sprag).

Have you considered a Gear Vendors unit for OD?