HELP/ADVICE -4BT swap into '82 GMC step van
Hi and thank you for your help and thank you for a very helpful site.
I plan on swapping a 4bt into my '82 GMC step van and would like any advice/suggestions to speed up the process and avoid any setbacks.
It currently has a 292 (4.9) I-6,4 speed stick,4:10,16.5x9.5 wheel tire combo,power brakes,manual steering & weighs 6,880 with me in it.
Currently used for ice cream vending,80% of the time 8-10 mph but I need to travel on occasion at 55.
I need to make it more fuel efficient and nimble so I also plan on rebuilding a TH 3L80 with straight cut gears and change the 4:10 gears.
Any advice on the rear gears,what pieces/components that I need to swap the trans and any advice on swapping in the 4BT?
I've been looking for a complete donor but no luck.
Thanks again to any one that can offer any assistance.
Ice Cream Man
Any reason why you want a 3L80 instead of a turbo 400 (did the 3L80 have a lockup converter)?
If you are looking for a 4BT still, you might try for one out of a Chevy chassis van, as it should come with a TH400 screwed to it.
If yo decide you have to change the trans anyway, why not a 4L80E.
You shouldn't have to build it up as much, unless you are planning on crazy power and the controllers out there have come down in price a bunch (I've seen a thread about an Optishift group buy, don't know if it's still open) and of course there's the overdrive.
How much "more nimble" (I take that to mean more power) do you need it to be?
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If this is a P30 dual rear wheel van and not a P20 single rear wheel van I would recommend finding a Dodge 92 or 93 6BT engine with the A518 overdrive transmission. Get the engine complete with all of the coolers, the radiatior, etc. Mount the radiator in front of the radiator support. This gives you a heavy duty transmission that is double water cooled and has overdrive.
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90 Dodge W250 6BT Cummins 5 speed Getrag
91 Dodge W250 6BTA Cummins NV-4500 conversion
Originally Posted by nexxussian
I was told the 3l80 has straight cut gears making it a more durable trans in a 7,000 lb vehicle and I'm trying to stay away from purchasing electronics to keep costs low.I don't know if any of the one's that I've found have a lockup converter.
I've looked around for a 4BT but can't locate one locally.What other vehicles or equipment could I find 1 in?
By "nimble" I mean quicker around town.The 4 speed stick & 4:10's make her a slug/slow.
I'm trying to find out as much as I can before I do the swap so down time is cut down as much as possible.
Thanks for your interest and help.
No,it's not a dual rear wheel setup. I need better fuel economy than the I6 292 and was told that the 4BT would haul the step van around no problem and double my fuel mileage and be much more economical than the 6BT. Is this true? Thanks very much for your advive. I need all the help I can get.
Lockup converter seems to be worth 200-300 rpm at the top of the range.
It stands to reason that straight cut gears would be stronger, I don't know if that's necessary in your application.
If you were going to tow heavy loads, and shock load the trans with the engine turned way up, sure, but the use you describe isn't that horrible.
If you have the 3L80 core, and the rebuild parts, go for it, but I would expect the Turbo 400 that Cummins would use in the repowered Chevy box vans to hold up fine with the proper converter and a good enough cooler.
If I read your posts correctly, you have your van loaded to 7000 Lbs ish, IIRC the delivery vans with the 120 HP 4BT were rated (and used) at 10,000 Lbs +.
For whatever that's worth.
Other equipment with 4BTs for power include portable air compressors, gensets, and aircraft ground power units, that I know of.
I'm sure there are others.
If, on the other hand, you aren't insistent on a gm trans (if you already have one, please disregard) there is always the 47RH.
Overdrive, lockup, and no computer required. If you wanted one, get one from behind a 6BT, it's already stronger.
That should allow you to use the dodge spec flywheel housing, flywheel and bolts.
I've been told that the overdrive and converter lockup can be controlled with a switch (each), but I seem to recall there is a control box available for them that allows some automatic functioning of those, and doesn't cost obscene amounts.
All you should need to know about that to make an informed decision should be in the tech stickey under "transmission". (IIRC, might be "drivetrain", kinda tired at the moment )
I can help
I can probably help you out some. I just saw a 47RH transmission for sale if you want to go the Dodge route. I also have a 4BT; however, I haven't advertised it for sale yet.
1987 Mercedes 300SDL (D stands for diesel); 152K+ miles
4BT into a 00 Dakota 4wd
<--- my build thread
various other random diesel projects
Originally Posted by nexxussian
A friend of mine who is a transmission specialist/biz owner suggested the 3L80.He likes to overbuild,less chance of breakage.
I'm not that mechanically savvy so I don't know how to answer to you or understand clearly about the torque converter and how it plays into my particular need/application.Forgive me for my current lack of knowledge.
Yes,7,000 lb's with me in it.6,880 to be exact but I may install other equipment in the future such as a generator,RV - roof mounted AC.Doubt I'll ever go over 10,000 lb's or near it.
Will a 4BT bolt up to the 3L80 or a TH 400?I hope to replaace the I6 292
Thanks again greatly for your time,assistance and knowledge
With an automatic it's all about making the combination match your planned use, vehicle and engine, choosing the correct converter is part of that (much more involved than just finding one that physically fits into the trans).
Nothing wrong with over building, it usually means less maintenance in the future.
When the 4BT was put in a chevy chassied box van, like yours, they were screwed to a turbo 400.
Unlike the 292 you have, the part of the engine that the transmission bolts to on the 4BT unbolts from the engine.
It's called a flywheel housing and since it unbolts it can be swapped with one that uses a different pattern.
All of these are a matched set though, so if you are planning to change, make sure you get the housing, flywheel (and it's bolts) as well as the starter, any spacers or a "wave ring" if equipped.
Some of it may interchange, but you don't want to try and figure it out while you are assembling it.
Point being, if you get an engine that already has the Chevy pattern flywheel housing, and all the bits, you should be golden as it's the same pattern housing your 292 has.
I don't want to get your hopes up though, I don't know if your trans will cooperate with that setup (as I recall you have a stick, and I don't know if the Cummins flywheel will accept a clutch disc, or if you need a different flywheel, I'm sure that's in the stickies, but I haven't looked for that).
From what I read, if you decide to go with the Dodge trans you can (supposedly) get the flywheel, housing and all the associated parts off a 6BT out of a Dodge Pickup, they tend to be cheaper as they are more common than the Ford and Chevy pattern housings as they were only used in repowers (repower is when they replace the engine that came in a vehicle with a different one, here we call that a swap).
As always, best of luck, but if you are that mechanically disinclined, a swap may not be for you.
Yes Cummins did it in their repower program, but unless you are ready to duplicate their setup, it will likely get cost prohibitive as the tuning required to match a non standard combo isn't especially difficult, but it can be time consuming and shop rate adds up fast.
Your 292 can be made both more powerful and more economical, just an option.
If you are willing to learn how to work on it yourself, it can be a very rewarding experience, not to mention it's real handy to have the skills if you are in the middle of nowhere and it decides to be cantankerous.
Not trying to discourage you, but it bears mention, especially when you mention you aren't particularly mechanically savvy.