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I've been having a shift issues with my TH400 transmission since I bought this '68 J-3500. Today I finally had time to look into it. Figured I either had a vacuum leak or the vacuum modulator was bad. So, when I went to pull the modulator I found something different. Instead of just the modulator, there is also a 60 deg. adapter it mounts to on the transmission. This is to make clearance to the front drive shaft. As the original style modulator would hit the drive shaft if installed normally. I found NOS modulators and that is not a problem. The issue is with the adapter.

I currently have a new style vacuum modulator installed that fits fine and did fix the shift issue, but I'M trying to keep this totally old school and would like to replace it with original stuff if all possible.

Has anyone ever seen an adapter like this? (see pic's below) I've been googleing it all weekend and haven't found a single picture or info on this adapter yet. The curved piece and roll pin fell out when I removed the Modulator from the adapter. I figure this was the plunger that actuated the transmission via the adapter.

(btw, these are the cleaned up pictures. When it was first removed it looked more like a ball of black mud/crust. It took about 30 minutes with a screw driver chipping away at it to clean it to this point.)

Those are very hard to come buy.. If you find one it will be very pricey . I do not now how many years that they used those angled adapters . I have one but it is on a complete transmission out of a 1974 Cherokee so that gives you a 6 year span. I have seen then go for as much as a 100.00 bucks .GOOD LUCK

I don't like them because they fail more frequently than the newer style. They changed them for a reason. Do you want original or do you want it to work?

Did you get a new style 'Adjustable' modulator? Replace any rubber on either ends of the metal line to the manifold with new rubber. Take the metal line out if you can and clean it out with parts cleaner and blow it out with air afterwards. I was surprised what came out of the metal line on my 79. Good clamp on the rubber hose down at the modulator is a good idea too.

Yes, I did get the adjustable module along with all new rubber. The metal line no longer exist's, so no issue there. Everything from the module to the manifold is new.

As for the adapter. I can wait until I find one on the cheap. I have something that works installed in it's place right now. Plus, this isn't a normal driver, so it can sit if need be. There is a transmission scrap yard nearby that I'm going look at Monday. I might, doubtfully, get lucky and find one that won't cost a fortune.

I get the fact the new style stuff works better. The idea here is to keep it as old school mod "original" as possible. From when the engine swap was first completed in the very early 70's. That goes with a pain in the ass stuff as much as it does the cool stuff. Everybody does Chevy small blocks, 4L80E's and ford 9". That's why I'm keeping the Buick 430 with original points ignition, TH400, Dana 20 and Dana 53 rear axle. It's not because they work better, as they don't, but rather that's what they had back then. I believe some of that old school mod stuff needs to be preserved. Yeah, you just don't see that stuff anymore "for a reason", but sometimes you still need to keep some of the past to appreciate the current.

Faded, I agree with you 100%. I bought a 79 Chief because I like the 1979 technology and the ease and simplicity to work on these vehicles. Coming from the 67-72 Chevy truck restoration world, I have a deep appreciation for preserving factory equipment. I have found that aftermarket and re-pop parts rarely meet the quality level of OEM. China and Taiwan aren't known for sending us their 'best' of anything. lol

I've got that whole assembly I could send you if you pay shipping. I've thrown so many of those away it's not even funny.

What modulator goes in its place.??? Cnt get new 1 to fit??

HeavyMetalThunder_81 wrote: ↑Mon Sep 24, 2018 6:39 pm I've got that whole assembly I could send you if you pay shipping. I've thrown so many of those away it's not even funny.

Oh, man! I haven't been to this post since it was original. I never saw a notice for your reply. Should you see this and still have one, let me know. I would still be interested.

Sorry for bringing up such an old post, but its still worth trying.

fadec wrote: ↑Mon Nov 18, 2019 1:10 pm

HeavyMetalThunder_81 wrote: ↑Mon Sep 24, 2018 6:39 pm I've got that whole assembly I could send you if you pay shipping. I've thrown so many of those away it's not even funny.

Oh, man! I haven't been to this post since it was original. I never saw a notice for your reply. Should you see this and still have one, let me know. I would still be interested.

Sorry for bringing up such an old post, but its still worth trying.

Being so long ago it probably got thrown away, honestly lol sorry

I have one laying in my parts ..BUT....there is a direct replacement that my Trans rebuild guy installed …..That's why I have one in my parts box...
I'll get info and a foto by tomorrow...also, there is a piston like pin missing in your fotos , it's about 2-1/2 " long

HeavyMetalThunder_81 wrote: ↑Wed Nov 20, 2019 7:16 am Being so long ago it probably got thrown away, honestly lol sorry

No problem. Was worth a try.

itselliott wrote: ↑Wed Nov 20, 2019 11:45 am I have one laying in my parts ..BUT....there is a direct replacement that my Trans rebuild guy installed …..That's why I have one in my parts box...
I'll get info and a foto by tomorrow...also, there is a piston like pin missing in your fotos , it's about 2-1/2 " long

Yeah, I knew I was missing parts the second I took it apart. How and why they put it together like that is beyond me. If you have one that is complete, I'll take it.

Oh, and I finally fixed the notification's settings. I should now get an email when there is a reply.

fadec wrote: ↑Sat Nov 23, 2019 10:41 pm

itselliott wrote: ↑Wed Nov 20, 2019 11:45 am I have one laying in my parts ..BUT....there is a direct replacement that my Trans rebuild guy installed …..That's why I have one in my parts box...
I'll get info and a foto by tomorrow...also, there is a piston like pin missing in your fotos , it's about 2-1/2 " long

Yeah, I knew I was missing parts the second I took it apart. How and why they put it together like that is beyond me. If you have one that is complete, I'll take it.

Oh, and I finally fixed the notification's settings. I should now get an email when there is a reply.

What is your location?

itselliott wrote: ↑Mon Nov 25, 2019 6:00 pm What is your location?

PM sent.