C4 Tech/Performance L98 Corvette and LT1 Corvette Technical Info, Internal Engine, External Engine

Th400 rebuild..

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Old Apr 22, 2015 | 07:40 PM
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Originally Posted by Chevrolet12
Also my speedometer hole is in the case not the extension housing..
Yes that's correct. I got somewhat carried away there trying to mix/match.
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Old Apr 22, 2015 | 07:45 PM
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It's fine.. So is there no adapter I can thread on where the cable would go that I could plug in the speedometer connector?
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Old Apr 22, 2015 | 10:12 PM
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All you need is the reluctor wheel and VSS.
It will output the same signal as the 700R4's reluctor wheel and VSS.

The 700R4's VSS might look like it will work but the o-ring groove is further outward. The th400's reluctor wheel has a larger ID.

Otherwise it will all put out the same signal.

1988 GMC sierra 2500 parts would work.

Last edited by 8a8mfh; Apr 22, 2015 at 10:16 PM.
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Old Apr 23, 2015 | 04:44 AM
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Originally Posted by 8a8mfh
All you need is the reluctor wheel and VSS.
It will output the same signal as the 700R4's reluctor wheel and VSS.

The 700R4's VSS might look like it will work but the o-ring groove is further outward. The th400's reluctor wheel has a larger ID.

Otherwise it will all put out the same signal.

1988 GMC sierra 2500 parts would work.
That style cluster used a "plug-in" chip for the cluster that you broke off legs of the plug-in for various tire diameters. Old bodied trucks used a module for the same. Some have engineered "dip-switch" arrangements for the style cluster you mention. I'm quite sure the signal out of the VSS won't satisfy the speedometer request. I used a few of these for various SS 454 cluster exchanges and various tire sizes for a dually. I might still have a couple.

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Old Apr 23, 2015 | 07:22 AM
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??????????????? If he takes out a 700R4 with a 40 tooth reluctor wheel and puts in a th400 with a 40 tooth reluctor wheel the entire rest of the car will not "know" anything is different.
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Old Apr 23, 2015 | 08:38 AM
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Originally Posted by 8a8mfh
??????????????? If he takes out a 700R4 with a 40 tooth reluctor wheel and puts in a th400 with a 40 tooth reluctor wheel the entire rest of the car will not "know" anything is different.
That is NOT what he's dealing with. His original used a mechanical drive/driven lets say 17/38 ('84) and not an electronic pick-up ('94 in which case maybe it would be an easy swap). Any electronic pick-up method requires some sort of calibration done by a DRA, DRAC or some sort resistance altering device for speedometer/odometer.

The Painless piece "could" work, it's intention was for ECM controlled engines that required VSS input for control.

Last edited by WVZR-1; Apr 23, 2015 at 08:51 AM.
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Old Apr 23, 2015 | 09:03 AM
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Idk what I need.. My engine is converted to carb. If that makes a difference. It's a 385 stroker. And I'm really not too worried if it dead accurate as long as it's working.
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Old Apr 23, 2015 | 09:23 AM
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Originally Posted by Chevrolet12
Idk what I need.. My engine is converted to carb. If that makes a difference. It's a 385 stroker. And I'm really not too worried if it dead accurate as long as it's working.
If it's that heavily a modified piece then maybe consider a cluster change with an aftermarket electronic gauge pack that could use the TH400 VSS and reluctor feed. Not inexpensive I'm sure but it's maybe a solution. The TH400 reluctor might be a difficult find, it's likely NLA from GM so it might take a JY find. I don't know but maybe GearVendors might offer the reluctor wheel, the VSS is likely still available in the after-market. Take the OE/GM and have NAPA or someone change it to theirs.

Do you have the drive and driven from the TH400 still? How many on the drive? The driven? The drive/driven could be used that should make the speedo correct and then if the Painless worked as thought you would have a functional speedo/odo.

If you found a JY 1-ton G-van or old style GM 1-ton truck (with vent window), '90 or '91 you could maybe gather the reluctor and VSS for cheap. The 1-ton truck needs to be a 2WD.

Last edited by WVZR-1; Apr 23, 2015 at 09:36 AM.
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Old Apr 23, 2015 | 10:12 AM
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Dakota digital has an adapter to convert the th400 to vss but they can't tell me if the 700r4 vss would be the same as any other 700r4... Shouldn't that one work?
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Old Apr 23, 2015 | 10:22 AM
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Originally Posted by Chevrolet12
Dakota digital has an adapter to convert the th400 to vss but they can't tell me if the 700r4 vss would be the same as any other 700r4... Shouldn't that one work?
What is their product number?

I've just looked at their 8K offerings that convert cable driven but then I believe you would still need the DRA from them. You would put your trans together with what you have and buy 2 products from them I believe. Maybe from them an SEN-01-1 plus their DRA to convert the 8K. Very similar to the Painless offering but less expensive and no cable connection to terminate from the looks of it.

Last edited by WVZR-1; Apr 23, 2015 at 10:31 AM.
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Old Apr 23, 2015 | 10:26 AM
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Sen-01-1
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Old Apr 23, 2015 | 10:28 AM
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They asked me how many pulses per mile....
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Old Apr 23, 2015 | 11:12 AM
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Originally Posted by Chevrolet12
They asked me how many pulses per mile....
4K for speedometer.

If you used the correct gears "maybe" the painless works with no DRA. You might be able to land one of those "for cheap" eBay or wherever.

Yours is a very different "ONE OF" so give the entire project maybe to DD and let us know what works. I've seen the Painless done for numerous resto-rods successfully. If you used the TH400 reluctor/VSS you would still need the same DRA like I mentioned from DD or someone else. Does someone do a cable to 4K like the DD? I've never looked. Abbott is where I'd look if I were considering a DRA first. More expensive but quite reliable. I've used Abbott many times.

Last edited by WVZR-1; Apr 23, 2015 at 11:19 AM.
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Old Apr 23, 2015 | 11:13 AM
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That one should be correct then. Cool. Thank you
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Old Apr 23, 2015 | 11:28 AM
  #35  
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Originally Posted by Chevrolet12
That one should be correct then. Cool. Thank you
Ask them about a 4K cable adapter for GM, they may have done in the past for their cruise-control packages and just don't offer it any longer "as cataloged". Maybe some old stock on their shelves. The only important thing is the GM cable drive connection.
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Old Apr 23, 2015 | 11:31 AM
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Ok I will.. The sensor they gave me the part# for should convert from cable to electronic and plug right in they said.. Just needed to make sure it was 4k
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Old Apr 23, 2015 | 11:45 AM
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Originally Posted by Chevrolet12
Ok I will.. The sensor they gave me the part# for should convert from cable to electronic and plug right in they said.. Just needed to make sure it was 4k
If they're mentioning a single piece replacement then you're going to need to do the internal transmission drive/driven to provide the correct revolutions for the DD to convert. That's why I asked what you had. Drive number of teeth, driven number of teeth. A potential ratio for the 27" & 3.07 might be 18/38, other combinations might be possible depending on what you've got in hand.

Ask DD if that's not correct. One piece can't do all of the correction.

I saw their specs on the SEN-01-1 as an 8K

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Old Apr 23, 2015 | 01:18 PM
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Maybe I wasn't paying attention... I can call them back and make sure. I know one of them was 4k. And as long as it's close I would be happy.
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Old Apr 23, 2015 | 01:29 PM
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I will also pull the gears out of the transmission and see what's in it
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Old Apr 23, 2015 | 04:28 PM
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Called them back and I was wrong again.. Sorry. They said it's 8k.and they sell something else to lower the output to 4
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