Swapping a SM465 with TBI

[JCampbell]

I’m really considering ditching my TH400 and replacing it with a SM465 in my dually.

I like the durability of the 465 and the fact that if anything were to go south with it, the general consensus is that anyone with a Craftsman tool set can tear one apart and completely rebuild it. Plus, I like shifting my own gears in these trucks. Granted, I won’t be doing any speed shifting or drag racing, but c’mon, it’s a 1-ton truck, not a Porsche.

I have a handle on the mechanic’s of the swap, but I’m specifically curious to know how this will affect my TBI swap. Different VSS I assume. Also, I read on Novak’s site that the later-model 465’s (‘88+) had a switch for a lean cruise condition in the ECM. Should I be on the lookout for a late model trans? Looking at you, RFMaster.

Any thoughts, experiences, or opinions?

[rfmaster]

No experience with SM465, but I did one swap TKO-600 in a Camaro.

1) Depending on the SM465 variant VSS selection should be basically the same - i.e. inline with speedometer cable 2000 ppm unit.

2) The top gear switch can be wired into ECM harness and basically equivalent to forth gear indicator line used in 700R4 applications. Incidentally, EPA forced GM to disable lean cruise due to increased NoX levels when engine is running AFR above 14.9:1 (Lean cruise can improve highway gas millage by 2 MPG in SBC 3/4 ton truck!)

In other words - go for it, but keep in mind that we'll have get you a manual box ECM EPROM calibration (readily available). To optimize this combo 454+ SM465 some DIY tuning will be required.

//RF

[1BadAction]

VSS should be located in the speedometer head, so that can likely stay the same as long as your speedometer is reading correctly.

I would get it tuned for the manual trans, though. There are differences in timing tables for the manual trans vehicles vs the autos (at least the ones that I've seen) That said, I swapped a T56 into my 5.7 TPI IROC in the late 90s and drove it for at least 2 years on the stock tune.

[JCampbell]

Originally Posted by rfmaster

In other words - go for it...

RF, you’re the man. I’ll definitely owe you a few cases of brew by the time this truck is done.

[JCampbell]

Originally Posted by 1BadAction

VSS should be located in the speedometer head, so that can likely stay the same as long as your speedometer is reading correctly.

Good to know. Thanks!

[rfmaster]

Originally Posted by 1BadAction

VSS should be located in the speedometer head, so that can likely stay the same as long as your speedometer is reading correctly.

I would get it tuned for the manual trans, though. There are differences in timing tables for the manual trans vehicles vs the autos (at least the ones that I've seen) That said, I swapped a T56 into my 5.7 TPI IROC in the late 90s and drove it for at least 2 years on the stock tune.

Exactly, just keep in mind that 1977 dash uses old school mechanical 1000 revolutions per mile travel speedometer. There is no built in VSS. To get around this minor inconvenience I use inline 2000 PPM VSS module from JTR.com. That's take care of about 99% conversions.

SA, tables are different between auto and stick. There are other subtle differences in IAC routines. IMHO realistically we'll have to spend a little bit of time dialing in VE, AE and PE tables once all said and done. Just make sure that beer is cold when it is all done (and bbq lit)

//RF

[Jonboy]

You can use the 2PRS VSS from stealth conversions (Jags that Run) that will go inline with the speedometer cable (preferrably right on the trans to avoid any signal interference from speedometer cable bounce). This is what I used on my '74. It also allows you to use the original cluster, too.

edit- RF sure types fast.

[1BadAction]

Doh, I thought he was refering to the 88. I agree, in the case of the older cluster, the JTR adapter is the best bet. It also eliminates the speedo bounce problem and I think they are more reliable than the ones in the cluster...

[JCampbell]

Originally Posted by rfmaster

Just make sure that beer is cold when it is all done (and bbq lit)

//RF

Roger that.

[JCampbell]

Well, everything for the TBI swap, including the cluster, will be sourced from the '90 Suburban donor I picked up.

[1BadAction]

Originally Posted by JCampbell

Well, everything for the TBI swap, including the cluster, will be sourced from the '90 Suburban donor I picked up.

In that case, that's an electronic speedo. Make sure you get the correct VSS and you should be good to go.

[JCampbell]

Cool. Thanks.

[JCampbell]

Originally Posted by rfmaster

The top gear switch can be wired into ECM harness and basically equivalent to forth gear indicator line used in 700R4 applications. Incidentally, EPA forced GM to disable lean cruise due to increased NoX levels when engine is running AFR above 14.9:1 (Lean cruise can improve highway gas millage by 2 MPG in SBC 3/4 ton truck!)

Okay, wait…

You’re saying the lean cruise was deleted by the EPA, so I don’t need to look for a late-model trans with the top gear switch, but, if I go with that programmable ECM you were telling me about, won’t I need the late-model trans if I want to use the lean cruise?

I’m lost.

I want to enable lean cruise when it’s all said and done. What do I need to do that?

[rfmaster]

Originally Posted by JCampbell

Okay, wait…

You’re saying the lean cruise was deleted by the EPA, so I don’t need to look for a late-model trans with the top gear switch, but, if I go with that programmable ECM you were telling me about, won’t I need the late-model trans if I want to use the lean cruise?

I’m lost.

I want to enable lean cruise when it’s all said and done. What do I need to do that?

I would keep my options open.

If you get late model box - hook up switch to the harness (forth gear indicator).
If you get older version of the trany - ECM can live without high gear indicator switch. I'll have to research this configuration for a stock ECM. In either case to enable lean cruise the ECM firmware needs to be updated (or to put it correctly lean cruise patch applied). This can be done at much later date, when basic particulars have been addressed.

Side note
The EBL upgraded ECM does not require high gear switch - it uses VSS signal as one of many parameters when to enable lean cruise. It can be readily configured to ignore 4th gear indicator (set option bit).

//RF

[JCampbell]

Roger that.

If I can source a late-model trans, I'll pick one up, but if not, an earlier-model will be sufficient.