Dave M

Hi,

I recently replaced a bad tranny (G58) with a W56/RF1A combo on my 91 ext. cab and I was saddened to find that I no longer have shift on the fly capability. I do a lot of driving on intermittently icy roads and this is must have feature for me. My question is where can I find a forward shift RF1A with syncros? I think they might have been available on trucks with automatic hubs and possibly 4 cyl. trucks with ADD although I think most came with the G series trans? If I can get one I'd be more that happy to trade a perfectly good forward shift RF1A. Any other info or help would be greatly appreciated.

Here is my other thought if I can't find one. I could put a solenoid that would bypass the vacuum switches that run the disconnecting diff. and hook it up to a switch in the cab. I would hit the switch, the ADD system would see vacuum without the case lever being moved and connect the differential. This would cause the entire front drivetrain including the front driveline to start rotating, correct? Then, assuming I wasn't in some soft of crazy rear wheel spinout my front and back drivelines would be rotating at the same, or nearly the same speed and the lever would easily slide into 4hi, hopefully without any horrible grinding noises or huge repair bills. So, does this idea work? I guess it all depends on if the diff is normally connected by the ADD system before or after the case lever is thrown. I suspect that it's after in which case this won't work and instead of a terrific grinding in the case, I'll get a terrific grinding in the diff. The other option would be to connect permanent vacuum to the diff but I really don't want my front driveline rotating all the time. Thanks for any help, a have a great Christmas!

Dave

MMA_Alex

my rf1a shifts fine on the fly. only issue is shifting out of 4wd if you get some binding by driving on dry roads you have to back up a little sometimes to relieve the strain to shift back into 2wd.

seafarinman

I have a perfectly good forward shift VF1A transfercase from a G58 transmission that is just sitting in the garage. Where are you located?

Dave M

Thanks for the help!

MMA_alex: It sounds like you have one with syncros in it, and that's the kind that I'm after. Mine is absolutely not shift on the fly, I get really bad grinding if I try to push it even at speeds around 10 mph or so. I also get some binding when I try to shift out that I didn't have with my chain driven case. I've found if I hit the gas hard for a second and then let off right before I shift out it helps.

Seafarinman: Does the VF1A bolt to a W series tranny? I don't think it does but I'm not sure. I really don't wan't to have to switch trannies, just cases. I'm actually in your neck of the woods, or at least I am when I'm not on Christmas break.

MMA_Alex

I wasn't aware there was one with and one without.

DeathCougar

iTrader: (23)

A VF1A will not bolt to a w56 trans. First of all the VF1A is a chain drive case, and the RF1A is a gear drive case. Second would be the splines on the input shaft. Gear drive cases use a 21 spline (23 for turbo) input shaft. Chain driven VF1A cases use a 26 spline input shaft.

The RF1A (gear drive) Does NOT have shift on the fly capabilities.

Alex: Are you sure you do not have a chain drive case? And what speeds can you shift into 4x4 at? Chain driven cases can be shifted at up to 50mph.

MMA_Alex

I have a w56, and as far as i've read the rf1a is the only t-case they used behind it. I haven't shifted at high speeds typically 10-15mph.

DeathCougar

iTrader: (23)

Does it grind in at all? I cannot make my RF1A cases shift in anything but under 5mph. Maybe the later model cases shift easier at slightly higher speeds. Not sure. But I do know they are not technically designed to be true shift on the fly.

The chain driven VF1A cases were only used in trucks with ADD, so it really was a true shift on the fly option.

MMA_Alex

no grinding, just tends to get stuck in 4x4 when you make a lot of turns in good traction situations, and then try to shift back to 4x2. I just ran out and checked and it does have the 7 bolts on the cover which would indicate its a rf1a. I tend to shift at low speeds, while coasting to keep strain off the case while shifting.

DeathCougar

iTrader: (23)

well perhaps they can be shifted up to 10-15 then. But still, a chain drive can be shifted at up to 50. Methinks your trans wouldn't agree to that one lol.

I sometimes have issues getting mine back out of 4WD. It off an on, likely just the position of the gears. A little slow forward driving, and everything is right as rain.

JamesD

On my 87 I had a G58 with a RF1A and I could shift on the fly up to 60 mph. The only problem I had was going from 4 to 2. Sometimes it wouldn't go until I was going slow around 20. So I do not know what you are talking about.

James

Dave M

MMA_alex: What type of truck do you have? I'm almost sure some trucks came with R1FA's with syncros in them. If you can shift into 4 at 15 mph without grinding then yours probably has them. My syncro-less case will grind at pretty much any speed.

JamesD: Did your truck have auto hubs (not ADD or manual)?

MMA_Alex

They didn't use auto hubs on 93's. I believe mine came with the manual hubs, but i'm not 100% sure as i'm the 4th owner.

oh, its a 22re reg cab manual with the w56

Dave M

Yeah, auto hubs bit the dust (thank god) in 89

DeathCougar

iTrader: (23)

Well if yiou had a G58 trans, you would not have a gear drive RF1A case, you would have the VF1A chain driven case.

However, the 87 trucks didn't have a G58 from the factory, they gad the G54 with a gear drive forward shiftin case.

It is possible that the previous owner of your truck swapped the G54 out for the G58 and thats why you have shift on the fly capabilities.

The gear driven have no syncros, so they are not supposed to be able to be shifted on the fly. Dont know what to tell you in the case of your 87.

seafarinman

AHEM! My 1994 DLX truck has a R150F/VF1A chain drive case with manual locking hubs just as it came from the factory. (My hubs just have 30 spline Longfield hub gears in them now to mate up with the birfield joint behind them)

JamesD

Manual hubs.

James

JamesD

My bad I made a mistake, I had the G52/G54. It was a regular cab, manual hubs, carb 22R and bucket seats all factory. I was the second owner and personally knew the previous owner who bought it with only 10k miles on it so no nothing ever got swapped. Mine would have been a top mounted case.

James

JamesD

Mine is auto but has the V6 with manual hubs from the factory and it is shift on the fly as well.

James

DeathCougar

iTrader: (23)

lol i was refering to the G58 transfer case. Sorry didn't clarify that lol. Im not sure, but I dont think the case from a V6 truck will bolt up to a G58?