SM465 swap into 92 suburban.

[AyWoSch Motors]

Okay, i know its not a squarebody, but its not far off, and i involves alot of squarebody donor parts.
Have a 1992 GMC Suburban K1500, with a TBI 350, and a 700r4.
After 300k plus miles, the 700 is finally slipping, never been real pleased with it anyway, so want to manual swap it..
Im also working out doing a nv3500 swap into my 86. So that leaves me with a spare sm465 with nothing wrong with it. No the burb has a real high rear gear like 3:08 or somthing, so a non OD 4 speed will be fine.
Measured transmissions, the 700r4 amd the SM465 also are the same case lenght, same mount lenght, same bell housing, same T-case pattern.
Ive collected parts. I have a clutch pedal amd brake pedal assembly out of a 91 pickup. I have a clutch master cyl, line, slave cylinder. I have a flywheel off the 91 pickup. Also have a trans tunnel extension and cutout, shiftboot and trim peice for inside. I don't care about the column being auto.

Now my big questions are these...
1: is the output shaft spline count the same from a 86 sm465 to a 92 NP241 that was pairer with a 700?
2: will a squarebody bell housing with a external slave cyl on the drives side fit a 92 with the drive shaft on the drivers side, or will they collide.
3: will the speedometer still work? I think the speedo plugs in in the transfer, but not sure...
4: will a clutch set from a squarebody fit the 91 truck flywheel and match the trans? (Because the one in the 86 is nearly new)
And 5: will any of the TBI electronics care or will the computer have a panic attack not getting a signal from the transmission?


Any help is appreciated, thank you.

 

[nvrenuf]

I don't know much about the newer body style trucks but I do know the sm465's used in them had the shift tower located a few inches rearward of where the square body version was located. You may want to take some measurements and make sure the earlier forward placement won't interfere with the dash.

Is the sm465 from a 4wd or 2wd? A 4wd version will have a 32 spline tailshaft. I believe the 700 will be 27 spline as well as the input on 241. You'd need to swap input shafts on the 241 to fit the 32 spline sm465.

A 2wd sm465 will have a 35 spline tailshaft and will not any tcase regardless of application / year.

 

[AyWoSch Motors]

I don't know much about the newer body style trucks but I do know the sm465's used in them had the shift tower located a few inches rearward of where the square body version was located. You may want to take some measurements and make sure the earlier forward placement won't interfere with the dash.

Is the sm465 from a 4wd or 2wd? A 4wd version will have a 32 spline tailshaft. I believe the 700 will be 27 spline as well as the input on 241. You'd need to swap input shafts on the 241 to fit the 32 spline sm465.

A 2wd sm465 will have a 35 spline tailshaft and will not any tcase regardless of application / year.

Okay, good to know.
The sm465 is 4wd. Is currently paired with a np208.
I have 2 other NP 241s that were paired with a NV4500 and a 4L80E. Those should be the larger 32 spline input shaft.

As far as the shift tower location, i think ill be okay. I have alot of room there, and i will probably use the offset shifter rod thats orginal to the squarebody. The distance is closer in a 90s chevy than a squarebody. Should be okay.
Thank you.

 

[bucket]

Your existing clutch will work, it's just standard Chevy stuff.

I don't think the squarebody bellhousing and slave will fit at all.

The TBI might behave ok-ish, but you might have some quirks like stalling at slower speeds with the clutch depressed, trouble light for EGR or other random stuff. Or it might be fine, there's really only one way to find out I think.

I think I still have a gmt 400 bellhousing for the 465, but it needs some work. There's some cracking at the trans mount holes and they have already been helicoiled, so it really needs welded and re-drilled I believe.

 

[AyWoSch Motors]

Your existing clutch will work, it's just standard Chevy stuff.

I don't think the squarebody bellhousing and slave will fit at all.

The TBI might behave ok-ish, but you might have some quirks like stalling at slower speeds with the clutch depressed, trouble light for EGR or other random stuff. Or it might be fine, there's really only one way to find out I think.

I think I still have a gmt 400 bellhousing for the 465, but it needs some work. There's some cracking at the trans mount holes and they have already been helicoiled, so it really needs welded and re-drilled I believe.

Good to know on the clutch.

Bummer on the housing...

A friend of mine told me the computer should be okay, because 92 was a dumbed down system electrically. Only think i was curious about was speedometer.

Hmm, tempting. If i can find one locally, id be interested in yours if for sale...

 

[bucket]

Good to know on the clutch.

Bummer on the housing...

A friend of mine told me the computer should be okay, because 92 was a dumbed down system electrically. Only think i was curious about was speedometer.

Hmm, tempting. If i can find one locally, id be interested in yours if for sale...

Yeah, hopefully you can find one local. If you got the one I have, there'd be shipping AND you'd still have to repair it too.

 

[AyWoSch Motors]

Yeah, hopefully you can find one local. If you got the one I have, there'd be shipping AND you'd still have to repair it too.

Understood. Thanks. Ill shop around here first, see what i can get.

I do have a friend thats good at welding aluminum.

 

[AyWoSch Motors]

Yeah, hopefully you can find one local. If you got the one I have, there'd be shipping AND you'd still have to repair it too.

Could you take a pic of it, if you get a chance? No rush..
I have a stack of bellhousings, wondering if i have one. Doubt it but who knows.

 

[PrairieDrifter]

Squarebody bell.

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GMT bell

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Crappy pic of the gmt bell lol
You can also kind of see the shift tower difference.

 

[Hunter79764]

I'm zero help, but I have a question you might be able to answer... On the SM465, especially with tall gearing, is it practical to use Low gear as 1st gear in normal/street driving? Or is the non-synchro that big of a deal? I've only driven two trucks with non-synchro low gear, and both were conventionally geared so Low gear was just for crawling around, basically, and both were 15-20 years ago and only ranch duty. I'm curious if a big tire/3.73 truck could use low as first gear, as "1st" would be pretty tall.

 

[legopnuematic]

Non synchro first isn’t an issue up shifting. Down shifting on the other hand is where the fun begins. Pretty much have to float it in.

In the Advance Design (47.5-55.1) trucks I had played with in years prior I would always start in first (low if you want to call it that), but being a fairly heavy straight truck, and fairly low power, stock worn 235 stovebolt (still a Babbitt beater!), as it was pretty much needed to get things moving. I had tried there and there starting off in 2nd (or first if you subscribe to the L123 instead of 1234), it would do it but required too much clutch to get things moving, in my opinion.

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[Hunter79764]

My 2 trucks I have experience with, one was a '48 Chevy, but it had been chopped up beyond recognition. a few feet cut out of the wheelbase, cab was essentially removed except for floor pan and firewall, dash was made out of the original tailgate but folded to be a trough that help misc hunting gear, and homemade sheetmetal fenders and hood. Fabric top on a copper tube frame, and flip up windshield... Fun truck on the hunting lease. But since it was so light and still had a 235 (but upgraded/replaced with a 60's model with forced lubrication way back in the 70's), starting in 2nd was no problem. It had a 57 passenger car rear end, not sure the gearing, and probably 29" tires. L/1st was about walking pace, and only used when going up the rough stuff or to literally walk alongside for doing road maintenance or things like that.
The other truck was a 73 3/4T, 4.10's and 32" tires I think. It was grandpa's hunting truck so I only drove it a few times and rarely used L gear. The only thing I really remember in particular was that the clutch was heavy, long, and out of reach for me as a 14 year old kid who didn't know that the bench seat could slide forward... Double clutching seemed to be the name of the game though, but no more than I go into 1st while moving in any stickshift I've driven, I'm tempted to think it would be fine for a swap on my Suburban.

Thanks for the side info, back to the regularly scheduled programming here

 

[nvrenuf]

If you need to use granny gear while street driving the truck is grossly under geared.

 

[AyWoSch Motors]

My 86 is 4:10 rear, and i use low gear 1st alot. Usually around the yard or when towing. Not usually in town just driving around. In my burb it should be even more usable.

 

[AyWoSch Motors]

If you need to use granny gear while street driving the truck is grossly under geared.

My buddy has a c20 service rig with ridiculously under geared rear. He cruises around and does burnouts in low.
We've done 140 in that thing on the highway.