700R4 to SM465 maybe

[SirRobyn0]

So I'm going to be up front. I don't really think I'll go though with the conversion but I have been thinking about it and I think it is worth while for me to explore and consider it before having my 700R4 rebuilt. If it makes enough sense financially I might do it. The truck is:

1984 C20 305 - 700R4 2WD

So this is my understanding so far.
I will need a SM465 & bellhousing bellhousing is different for mechanical vs hydraulic clutch pedal.
I will need a clutch pedal and linkage or slave and master
I will need a shift lever and a boot
I will need a clutch kit and a flywheel

Here's what I don't know / unsure of.
I think the transmission cross member might have to be moved, but I don't know that for a 100% fact.

This is an 84, with a low hump floor. Is that going to be a problem? I think by 84 the hump is no longer removable, and there really aren't any squares in wrecking yards around here so if I need to cut and paste a different hump in that might be a bit of a problem. At the very least it's an added complication I'd need to consider.

What about the driveshaft. Obviously I'd need a SM465 yoke, but not sure about the actual shaft itself if it would be the same length or different?

 

[AuroraGirl]

So I'm going to be up front. I don't really think I'll go though with the conversion but I have been thinking about it and I think it is worth while for me to explore and consider it before having my 700R4 rebuilt. If it makes enough sense financially I might do it. The truck is:

1984 C20 305 - 700R4 2WD

So this is my understanding so far.
I will need a SM465 & bellhousing bellhousing is different for mechanical vs hydraulic clutch pedal.
I will need a clutch pedal and linkage or slave and master
I will need a shift lever and a boot
I will need a clutch kit and a flywheel

Here's what I don't know / unsure of.
I think the transmission cross member might have to be moved, but I don't know that for a 100% fact.

This is an 84, with a low hump floor. Is that going to be a problem? I think by 84 the hump is no longer removable, and there really aren't any squares in wrecking yards around here so if I need to cut and paste a different hump in that might be a bit of a problem. At the very least it's an added complication I'd need to consider.

What about the driveshaft. Obviously I'd need a SM465 yoke, but not sure about the actual shaft itself if it would be the same length or different?

for a 1984 ,i seem to recall soemthigng about 4x4 driveshafts being interchanged and everythign else was set to make that work. but for 2wd...

My vote: too much work, and too much time. unless a donor is had

 

[SirRobyn0]

for a 1984 ,i seem to recall soemthigng about 4x4 driveshafts being interchanged and everythign else was set to make that work. but for 2wd...

My vote: too much work, and too much time. unless a donor is had

Ya I mean frankly that's kind of where I'm at too. "to much work to much time" I'm hoping some that has done a swap like this on a 2wd will come along. Like I said I'm unlike really to do the swap, but if it were cost effective enough vs having the 700R4 rebuilt, maybe....

I don't think I mentioned that in this thread my 700R4 is going out, so in the next few months I will need to something.

 

[nvrenuf]

Pedals are different mechanical vs hydraulic.

That said, Advance Adapters or Novac makes a conversion bracket to put a slave on a mechanical bellhousing.

You will need a pilot bushing or bearing also.

The crossmember will need to move and the driveshaft length will be wrong. The '85+ 4wd's interchange because GM standardized the crossmember location by manipulating the tcase adapter lengths so that will not apply to your 2wd.

 

[Frankenchevy]

You drive quite a few miles in the truck, correct? To and from getting feed, etc?

With the cost of fuel and not having an OD, it’d seem that you will soon eat into any savings you envisioned going with a 465 over a rebuild. Although, I doubt any savings would be had unless you already had all the parts.

However, if the load you’re placing on the truck means it’s rarely in OD locked up, none of the previous statement is applicable.

If that’s the case, a more simple and much more robust th400 would be worth considering.

 

[SirRobyn0]

You drive quite a few miles in the truck, correct? To and from getting feed, etc?

With the cost of fuel and not having an OD, it’d seem that you will soon eat into any savings you envisioned going with a 465 over a rebuild. Although, I doubt any savings would be had unless you already had all the parts.

However, if the load you’re placing on the truck means it’s rarely in OD locked up, none of the previous statement is applicable.

If that’s the case, a more simple and much more robust th400 would be worth considering.

Thanks Jeremy I've thought about that. My commute to the shop consists of country roads with 35 - 50MPH lmits and a state route with 55MPH speed limit, about a mile of freeway and then a bit of city traffic. I may or may not see an economy loss on that drive. The main thing I've actually thought as far as down sides is the relatively heavy clutch pedal in city traffic.

Ya, obviously when loaded I'm in drive, and that's when the manual would be nice, for the added control. So basically it would great if it had a 700R4 on daily basis and SM465 when I'm hauling....

In the automatic family I'd stay with the 700R4, even though it's not the strongest, the over drive and low first gear ratio are nice. The TH400 requires a driveline length change I can't remember if it needs to be longer or shorter but I remember reading it would need to be changed. The main attraction would be the heavy duty of the TH400. The TH350 is a direct swap for the 700R4, but what's the point in that... loose the low first, loose the over drive and don't gain much strength. I'd rather have the 700R4 built up a little bit for strength.

@nvrenuf Thanks for the info that's what I was afraid of. I don't mind the cross member move or the driveshaft really but it adds more to the project idea and for my purposes it's enough to kill it. Thanks.

I appreciate everyones thoughts. This is exactly what I thought would happen but I wanted to at least explore it. The end conclusion is for me it's not worthwhile to swap. I'll have the 700R4 rebuilt. Thanks.

 

[wanderinthru]

As much of an automatic hater as I am. It would be hard for me to go thru the trouble of changing to a standard instead of just a good rebuild of the auto. On top of that unless you have a known 465, it would need a good "going thru" before you went through the trouble of putting it in the truck.

 

[SirRobyn0]

As much of an automatic hater as I am. It would be hard for me to go thru the trouble of changing to a standard instead of just a good rebuild of the auto. On top of that unless you have a known 465, it would need a good "going thru" before you went through the trouble of putting it in the truck.

Yea, I mean that's my thinking too. And I just wanted find out what was involved that I wasn't aware of. The good thing about having an auto trans rebuilt is at least it will or should come back shifting more the way I want it too, so it'll still be better than before and that will be nice.

 

[wanderinthru]

Yea, I mean that's my thinking too. And I just wanted find out what was involved that I wasn't aware of. The good thing about having an auto trans rebuilt is at least it will or should come back shifting more the way I want it too, so it'll still be better than before and that will be nice.

HaHa Yes Sir. And if you were to have done it 10 times there will be things 'we were not aware of" on this one! Or, thats how it works for me. Plus, we need to think of the value of these old trucks. The closer to original they are the more value they hold, and they are getting valuable. I'm sure your like me and the old squares ain't for sale. Personally, my crystal ball been broke since the get go, and I've no idea what tommorow holds.

 

[SirRobyn0]

HaHa Yes Sir. And if you were to have done it 10 times there will be things 'we were not aware of" on this one! Or, thats how it works for me. Plus, we need to think of the value of these old trucks. The closer to original they are the more value they hold, and they are getting valuable. I'm sure your like me and the old squares ain't for sale. Personally, my crystal ball been broke since the get go, and I've no idea what tommorow holds.

Yea I hear you on the crystal ball thing. And you have a good point, it appears likely that I might have a numbers matching truck. I've not run the numbers on the motor but the tranny is from 84 so it's pretty likely the original. Whether it's been rebuilt before of not who knows...

 

[bucket]

Knowing what you do with the truck and your time constraints, a manual trans swap isn't for you. However, I do believe that having a th400 rebuilt to swap in may still be worth considering.

If having the 700r4 done, definitely have all the common upgrades done.

 

[Redfish]

Regarding #'s matching and all original...there are just too many of these trucks out there for it to matter. If you study the Results on BringaTrailer you will find that installing a modern engine and drivetrain makes the selling price of these trucks skyrocket. Same with the first Gen Broncos and the '67 to '72 era Blazers. A Coyote or an LS "upgrade" sends the price way up.

What does matter is that MOST folks want an automatic and that affects the resale. Only some of us Dinosaurs want to shift a manual transmission these days.

My Opinion (which is free and worth nothing) is that the SM 465 might not be a good idea from a towing standpoint regardless of price. Even though it is technically a 4 speed it gets used as a 3 speed 99 percent of the time. There is a pretty big dip between 1st and 2nd. That old 700R4 may actually put the power down better for towing. I realize that is a matter of opinion but I actually grew up driving a SM 465 in a 4wd GMC. The 4 speed 700R4 we had in Mom's '84 K5 Blazer was able to get the anemic 305 to pull decently...for that era.

I would rebuild that old 700R4 for all the reasons everyone else has stated and for the fact that you already know what you have and how it is supposed to feel and work. Swapping all of those components might be fine for a Play Toy. But this is a Work Truck. And a Very Good Work Truck at that.

 

[SirRobyn0]

Knowing what you do with the truck and your time constraints, a manual trans swap isn't for you. However, I do believe that having a th400 rebuilt to swap in may still be worth considering.

If having the 700r4 done, definitely have all the common upgrades done.

Thanks I think your right about the manual swap I just kind of wanted to gather a little more info on it. I thought about going to the TH400 at one point and also the TH350. Other than the TH350 is the same length as the 700R4 there aren't really any benefits that I can see. Although I know guys will debate the the gear ratios in the 350 & 400 are closer together and that can be a good thing, but I've come to like the lower 1st ratio in the 700, and I'd like it more with a lower rear end ratio. The benefit in the TH400 is the added strength, but the driveline length has to be changed, or am I wrong about that? If the 700 & the 400 are the same length I'd give it some consideration.

Regarding #'s matching and all original...there are just too many of these trucks out there for it to matter. If you study the Results on BringaTrailer you will find that installing a modern engine and drivetrain makes the selling price of these trucks skyrocket. Same with the first Gen Broncos and the '67 to '72 era Blazers. A Coyote or an LS "upgrade" sends the price way up.

What does matter is that MOST folks want an automatic and that affects the resale. Only some of us Dinosaurs want to shift a manual transmission these days.

My Opinion (which is free and worth nothing) is that the SM 465 might not be a good idea from a towing standpoint regardless of price. Even though it is technically a 4 speed it gets used as a 3 speed 99 percent of the time. There is a pretty big dip between 1st and 2nd. That old 700R4 may actually put the power down better for towing. I realize that is a matter of opinion but I actually grew up driving a SM 465 in a 4wd GMC. The 4 speed 700R4 we had in Mom's '84 K5 Blazer was able to get the anemic 305 to pull decently...for that era.

I would rebuild that old 700R4 for all the reasons everyone else has stated and for the fact that you already know what you have and how it is supposed to feel and work. Swapping all of those components might be fine for a Play Toy. But this is a Work Truck. And a Very Good Work Truck at that.

I am not tuned into values in the slightest. I don't watch Bringatrailer, and I do not like modern drive train in an old truck. To me that ruins them, I do like original, or factoryish. Hence the reason why when the 305 dies, I'll likely be putting in a 350, possibly mildly built, of course with hauling and towing in mind. (I will tell the builder the future plan when I get the 700R4 rebuilt). My point is from that prospective I do place some personal value on keeping a truck born an automatic and automatic. The big plus to the SM465 really is control and durability. I've already written off the SM465 idea really.

I haven't hauled a load in pickup with a SM465 in it in probably 25 years, but I get to drive customer rigs at the shop with them, and not this year but the prior several years a medium duty truck one of the valley farms owns during harvest, but as you'd expect it has a 2 speed rear end, which kind of changes things since there is 8 forward gears instead of 4. I also remember the amount of time it takes to change gears with an SM465 can be problematic when loaded or towing.

In the end it's all a trade off one way or another. I don't wanna rebuild the 700R4 and kill it in a couple years, I can hardly afford that, but on the other hand it made it all these years, and I've got a huge cooler and temp gauge. I've never overheated this one and I'll be sure not to do that to the rebuild. I do value the low first gear, and the over drive for the added economy when empty. When I eventually get around to changing the rear end gearing (currently 3.41 (Yikes)), keeping the 700R4 makes 4.10 or even 4.56 gears reasonable, even on the highway at moderate speeds (I did a lot of the RPM calculations a year or more ago)

Yea, she's a good work truck for me for sure and I'm sure I'll still be using it for work for a LONG time to come.

So if I have the local guy overhaul my 700R4, maybe while it's out I should be swapping that semi-float 3.41 ratio for that FF 4.10 or 4.56 I've been wanting for years now. I gotta get on my bicycle and find me a rear end and installation parts if that's going to happen.

 

[SirRobyn0]

Oh BTW @Redfish you said your opinion was worth nothing, and I disagree with that statement, it is valuable in my thought process anyway. In fact I'd say if your statement was a physical item it would probably look like hammered goat chit, give yourself some credit man!

 

[Redfish]

Oh BTW @Redfish you said your opinion was worth nothing, and I disagree with that statement, it is valuable in my thought process anyway. In fact I'd say if your statement was a physical item it would probably look like hammered goat chit, give yourself some credit man!

Well then, In My Opinion...

Your superb Work Truck should be kept with its original automatic transmission. I personally didn't buy a 1987 year model truck to put in a 2017 drivetrain. I wanted the original engine and transmission. The SM465 is a slow shifting transmission. It will never win any drag races but I love shifting it.

I do sort of keep up with the current market values and I know that a modern drivetrain drives the value up... but for me that completely kills any desire on my part to own that vehicle. I have a modern GMC with a modern diesel. There is a trailer hooked to that truck right now and I will be using it later today. But I will be getting in my '87 with its original motor and slow shifting original transmission to drive into Baton Rouge in just a few minutes. I will be trying to revive a 1982 Land Rover that also has its original drivetrain.

Also just an opinion... A man that treats his truck the way you do is probably going to have better "luck" with his transmission lasting a long time than the average man. You know that not everyone drives the same and not everyone performs proper maintenance.