727 doin the double bump

[towpainter3]

Ok this ones bafflin the hell out me. Just installed a transgo basic shift kit in my 727 and its double hittin when it goes into drive. I have checked the kickdown lever for proper adjustment and the shift cable. Both good.
By double hitting I mean you can feel it take the gear then it hits again as if its building pressure then fully engaging. I just installed the basic transgo kit, dont remember the number but it came with the new valve and some springs. Followed the directions to the t.
The tranny is good after the double hit. It shifts perfectly and kicks down great. No noises or slipping. And only does this in the forward gears. Any thoughts would be great. Im thinkin its in the v/b but cant figure why or what would be causing this. I cleaned the hell out of the v/b and the trans was in good workin order before. Talked with a guy who I wheel with,[ he builds trannies for a living] He said it sounds like a pressure apply problem, could something in the v/b cause this issue?

 

[towpainter3]

And as an added note it doesnt change hot or cold.
This pisses me off too. The damn thing shifts so good, quick solid shifts when your in the throttle normally and even better when you manually shift.

 

[Michael Mayben]

When you say "basic" transgo shift kit...what does that mean?

The tf-1 is a kit with very limited capability that primarily solves only the issue of torque converter drain back along with a few other items.

The tf-2 kit is full-featured and takes care of all known valve body issues as far as upgrading and enhancing durability and performance.

The tf-3 kit is for off-highway use only with full manual shift (no auto-shift).

Was this an ebay purchase of some really old transgo stuff that was maybe in a sealed poly bag with no id? Several years ago, the current tf-1 version was actually marketed as two separate "kits", one of the parts was called "no yo-yo"

also, did you adjust the bands as spec'd in the transgo stuff you just installed? The band adjustment specs for the transgo stuff is not the same as the oem specs.

The "double hit" deal is not something I'm familiar with.

I must know exactly which kit/parts you installed, then we can move ahead with this one. And by the same token, the various other brand names of these various shift reprogramming systems for the 727 vary tremendously in design and execution. And their parts don't mix and match with transgo parts even though some of the systems do call for similar/same mods.

Did you separate the upper and lower valve body segments and drill the separator plate and valve body channels?

 

[towpainter3]

Ok ill have to go back to the dacco dealer and get the part number for the kit, but it did only contain a new valve and a few springs and the seperator plate was drilled as per instructions in the kit. If I remember correctly there was no specific band adjustment instructions. I will get down there tomorrow or fri and get back. Thanks for the response I will get a copy of the instructions and the number off the kit

 

[towpainter3]

Ok ,m/m, after further investigation the transgo kit I installed was the sktfsc torqueflite shift kit, not the tf1.
There are possibly 2 issues I can forsee. The adjustment of the manual valve being to far in the partition or the adjustment of the pr valve which could be too loose. Not sure.I made no other mods to ths trans other than venting the cases and resealing. Spoke with a guy on the mopar forum and he suggested turning the pr valve adjustment in 3 turns to give it more pressure at the initial engage and during shifts any thoughts on this? Thanks in advance. Brad

 

[Michael Mayben]

The "sk® tfsc" is not a shift kit nor is it a shift reprogramming system. It is what was once referred to as the "no yo-yo" solution for a few specific potential problems that "some" 904 and 727 transmissions might develop. In other words, a fix for specific issues that the manufacturer never did address until several years after the fact, this is typical in the autotrans industry and most especially for any autotrans manufactured by the GM/hydramatic division.

In actuality, by the time ihc began using the 727, those issues had been corrected and only crop up after a rebuild when incorrect parts were installed instead of the updated stuff.

I don't mess with that repair part since it's not needed on the units I build which involve only the tf-2 or tf-3 shift reprogramming kits or the B&M equivalent of same. Therefore, I don't have the instructions for those.

As far as installing the replacement manual valve in that sk® tfsc kit, that is a no brainer, and none of that install involved separating the valve body as the other system do. If you installed the correct spring for your application, and then you adjusted the spring limits correctly, you will have a functional system that is completely benign in operation. In other words, it does nothing for enhancing or beefing the shift characteristics.

And when installing that transgo valve, you must set the spring stop exactly to the specification given, I totally disagree with what your other advice is regarding diddling control pressures as that is simply not possible unless you have a gauge set connected and fully understand what the ramifications of diddling will entail!

If it worked fine before doing the spring change (the replacement manual valve is not creating this issue, it can't!), then that is the problem, something was not adjusted by the instructions supplied with the parts.

I'd put it back like it was in the beginning. Then if you want to improve the overall performance of the slushbox, do the job right and install a full tf-2 shift reprogramming system.