700r4 wont go into 4th after rebuild, total mystery.
09-15-2011, 10:20 PM
#1
700r4 wont go into 4th after rebuild, total mystery.
So i rebuilt my 700r4 with a trans-go jr. shift kit, .500 boost valve and corvette servo. I used a rebuild kit with alto clutches and replaced all the piston seals down to the low-reverse pack. Lucky for me i have a trans dyno at my disposal so i didn't put it back in the car yet, thankfully. So everything shifts smooth up to 3rd gear. Reverse, 1,2,3 works perfect, but then you hear it trying to going into 4th gear but it doesn't happen. As it tries to go into 4th, the trans started heating up and white smoke poured out of the fill tube.
I pulled it apart and the band was smoked. I replaced the drum and band and put it back together.The clutches in the 3-4 pack were perfect, not even engaged once, but it still does the same thing. This time I shut it down before it got hot enough to burn up the band again. So far i tried with the original non vette servo, and three different valve bodies, two of which didn't have the shift kit. It still does the same thing. the check-***** are all in the correct places, and i air checked the clutch packs before putting them in. Also the line pressure is good.
I have no idea what to do next. If anyone has any info on this I would be greatly super duper Highly thankful. Everything i look up online doesn't say anything about this issue.
I pulled it apart and the band was smoked. I replaced the drum and band and put it back together.The clutches in the 3-4 pack were perfect, not even engaged once, but it still does the same thing. This time I shut it down before it got hot enough to burn up the band again. So far i tried with the original non vette servo, and three different valve bodies, two of which didn't have the shift kit. It still does the same thing. the check-***** are all in the correct places, and i air checked the clutch packs before putting them in. Also the line pressure is good.
I have no idea what to do next. If anyone has any info on this I would be greatly super duper Highly thankful. Everything i look up online doesn't say anything about this issue.
09-16-2011, 11:28 PM
#3
Re: 700r4 wont go into 4th after rebuild, total mystery.
I already checked that and it was good. I was thinking maybe the seals where the pump slides over the 3-4 drum. I replaced the half orange and yellow seals with the once piece white ones. I also got a 4l60e drum which holds an extra clutch and steel, so its a little more beefy. Its been air tested with the pump on top and everything is good outside of the trans. Between the new drum and seals it SHOULD work now. Just gotta get the rest back together and put it back on the dyno.
09-29-2011, 09:18 PM
#5
Re: 700r4 wont go into 4th after rebuild, total mystery.
Pressure was leaking past the seals on the end of the 3-4 pack where the pump slides on. I replaced those yellow/orange rings with the solid white ones and it shifts into every gear with no issues. Thankyou for the replies.
09-30-2011, 12:47 AM
#7
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Re: 700r4 wont go into 4th after rebuild, total mystery.
if you put the input sprag in backwards, it will smoke the band every time. No, it will fry the overrun clutches immediately. The 2-4 band will be fine. If the input sprag is in backwards, the vehicle will not move with the shifter in "OD" position, but will move in "D" position.
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09-30-2011, 10:10 PM
#8
Re: 700r4 wont go into 4th after rebuild, total mystery.
Because i didnt replace them when i initially put it back together. For some reason the rebuild kit i got didn't have the new seals. I just reused the crappy yellow and orange seals that aren't a solid piece. After took it apart again all i did was replace those seals with the updated ones and it worked. It probably didn't have enough pressure to fully hold the band do to some pressure leaking past one of those seals, which was why it burned the band up. Works perfect now though.
10-02-2011, 02:11 AM
#9
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Re: 700r4 wont go into 4th after rebuild, total mystery.
If you are talking about the 4 seals on the input shaft being a scarf cut and the rings not filling up the groove. They had all kinds of problems with those type of rings. Always replace them with the step cut solid type rings or the solid rings that are not step cut. The step cut requires no special tool to install them, and installs in seconds. Glad your problem is solved. I have not seen anybody use the early scarf cut rings since the early 1990's. The scarf cut rings on the back of the pump have never been a problem. Again, much easier to install than the solid rings here.
10-03-2011, 12:12 PM
#10
Re: 700r4 wont go into 4th after rebuild, total mystery.
if you put the input sprag in backwards, it will smoke the band every time. No, it will fry the overrun clutches immediately. The 2-4 band will be fine. If the input sprag is in backwards, the vehicle will not move with the shifter in "OD" position, but will move in "D" position.
10-03-2011, 12:16 PM
#11
Re: 700r4 wont go into 4th after rebuild, total mystery.
I always air test the input housing before I put it in the case, and again after I bolt on the pump -- the correct size air nozzle can fit in the holes where the valve body sends fluid through the case, through the pump into the shaft... learned that from trial and error, mostly error.... LOL
glad you found the problem. I always use the one piece teflons, I have the tool.
glad you found the problem. I always use the one piece teflons, I have the tool.
Last edited by greggbruce; 10-03-2011 at 02:56 PM.
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